MoSe₂ as Electrode Material for Super-Capacitor, Hydrogen Evolution, and Electrochemical Sensing Applications: A Review

Abstract

In the past few years, metal chalcogenides have received extensive consideration because of their excellent physicochemical belongings. Particularly, molybdenum selenide (MoSe₂) is a promising metal dichalcogenide which possesses decent optical, electrical, and chemical properties and can be explored for a variety of applications. MoSe₂ has been extensively used for several applications such as energy storage and sensing. Since the energy crisis is one of the major challenges of today’s world, super-capacitors and hydrogen evolution are promising energy technologies that may benefit the global world in the future. Thus, researchers have been motivated towards the strategy and fabrication of electrode materials for super-capacitors and hydrogen evolution applications. MoSe₂ is a multifunctional material, and previous years have witnessed the rapid growth in the publication of MoSe₂-based electrode materials for super-capacitors, hydrogen evolution, and electrochemical sensing applications. Thus, it is of great significance to merge the previous reports into a single review article on MoSe₂-based modified electrode materials for super-capacitors, hydrogen evolution, and electrochemical sensing applications. Therefore, we have compiled the previous reports on the design and fabrication of MoSe₂ and electrodes based on its composites for super-capacitors, hydrogen evolution, and electrochemical sensing applications. It is believed that this article may benefit the researchers working in the research field of super-capacitors, hydrogen evolution, and electrochemical sensing applications.

1. Introduction

In the previous years, it has been observed that carbon dioxide (CO₂) emission crossed 33 metric gigatons (Gt) annually which may increase the temperature of the earth [1]. In the present scenario, it is difficult to reduce the emissions due to the dependency of the present world on fossil fuels, which contribute a significant role in CO₂ emissions [2]. Therefore, it is clear that it is the need of today’s world to develop renewable energy sources for a neat, clean environment. Thus, the global pursuit of clean and sustainable energy solutions has brought about critical challenges associated with environmental sustainability and energy security [3]. Addressing these challenges requires the development of innovative materials capable of driving advancements across diverse energy-related technologies [4]. The development and utilization of renewable energy sources will not only diminish the dependence on fossil fuels but also decrease the severity of the energy crisis in the future [5]. In this regard, various kinds of energy technologies have been developed, but energy storage and hydrogen evolution are the two promising energy technologies which have received extensive interest from researchers.

Energy storage devices such as super-capacitors play a very vital role in modern energy systems and they bridge the gap between the batteries and conventional capacitors in terms of energy and power density [6,7]. Super-capacitors exhibit attractive features such as power density, charging-discharging duration cycle life, energy density, environmental friendliness, and cost-effectiveness [8]. Previous years have witnessed rapid growth in the design and fabrication of nanostructured electrode materials for the expansion of next-generation super-capacitors [9,10,11]. It is expected that super-capacitors with high specific capacitance may contribute towards energy-related applications [12]. Thus, the preparation of highly stable and cost-effective nanostructured materials with eco-friendly nature are desirable candidates for the construction of next-generation super-capacitors [13,14,15].

Recently, hydrogen (H₂) evolution has received wide interest owing to its environmentally friendly nature and cost-effectiveness [16]. In particular, electro-catalytic H₂ evolution reactions (HER) are a promising cost-effective and environmentally friendly approach to generate H₂ [17]. It is well known that HER is a half-reaction in the electro-catalytic water-splitting process [18]. The performance of the H₂ evolution in HER depends on the properties of the electrode materials [19,20]. Thus, the progress of vastly active and stable catalysts is needed for HER applications.

Recently, transition metal dichalcogenides (TMDs) have appeared as a class of versatile ingredients with wide-ranging applications [21]. Their atomically thin, layered structure and quantum confinement effects underpin their utility in areas such as sensors, batteries, optoelectronics, and other energy-related industries [22,23]. In particular, molybdenum diselenide (MoSe₂), a prominent member of the TMD family, has garnered growing interest due to its distinctive properties [24]. MoSe₂ also offers promising characteristics such as acceptable conductivity, which might be attributed to the intrinsic metallic nature of Se element [25]. MoSe₂ layered architecture, bound by van der Waals interactions, is structurally analogous to that of graphite, enabling it to serve as a viable alternative to graphene in certain applications [26]. In previous years, MoSe₂ has been explored for super-capacitors [27], HER [28], solar cells [29], and sensing applications [30].

This review proposes to deliver a comprehensive overview of the recent advances in MoSe₂-based electrode materials for super-capacitors, HER, and electrochemical sensing applications. The challenges, and future prospects for MoSe₂-based materials for recent super-capacitors, HER, and electrochemical sensing applications have been discussed.

Before the discussion of the MoSe₂-based applications, it is worthy to mention that MoSe₂ may have some toxic impacts on human health, thus, proper handling should be monitored before its use in the fabrication of electrodes.

2. MoSe₂-Based Materials for Super-Capacitors

Two-dimensional (2D) transition metal-based nanomaterials have attracted significant attention for electrochemical applications, owing to their extensive surface area and plentiful active sites. But, their effectiveness is often limited by challenges such as agglomeration and poor electrical conductivity, which diminish their electrochemical activity. To overcome these obstacles, developing advanced 2D hybrid nanomaterials is crucial for enhancing super-capacitor efficiency. In this connection, 2D MoX₂ nanostructures, particularly molybdenum-based materials like MoX₂ (X = S or Se), have shown significant potential in energy storage and harvesting applications, including high-performance super-capacitors. Specifically, MoSe₂-based composites are highly promising because of their adaptable oxidation states, high surface area, and excellent electronic conductivity. The energy storage capacity of super-capacitors is closely tied to the electrode structure and the capacitance-related properties of the active material. Engineering approaches to improve these characteristics are vital for achieving high-energy super-capacitors. Nevertheless, the widespread use of layered MoSe₂ is constrained by its low specific capacity, slow kinetics and considerable volume changes during electrochemical reactions. Vattikuti et al. [31] reported that homogeneous, dry, leaf-like mesoporous nanostructured MoSe₂ was effectively synthesized using a microwave-assisted technique. The mechanism for the construction of dry leaf-like mesoporous MoSe₂ can be seen in Figure 1.

Sophisticated characterizations such as high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) confirmed the formation of a unique leaf-like morphology and mesoporous structure in the synthesized MoSe₂ material. When tested as an electrode in super-capacitor applications, the MoSe₂ nanosheets attained a remarkable capacitance of 257.38 F·g⁻¹ at a low current density of 1 A·g⁻¹. Additionally, the MoSe₂ electrode demonstrated excellent long-term stability, retaining approximately 95% of its capacitance after 5000 charge–discharge cycles, highlighting its potential for energy storage and conversion technologies. In another study [32], NiSe/MoSe₂/MoO₂ 3D hierarchical hollow microspheres (HHM) were synthesized via a two-step growing and annealing progression, optimized for reaction time and Ni/Mo molar ratios. The authors performed FESEM and TEM analysis as shown in Figure 2a–i, correspondingly. The authors investigated the effect of time on the growth of the NiSe/MoSe₂/MoO₂ 3D HHM using SEM and TEM analysis. Figure 2a shows that the synthesized sample shows microspheres-like surface morphology which comprises various nanoparticles (NPs) and nanoflakes. In addition, Figure 2d,g indicate that the obtained sample is fully solid. At 8 h, the authors found that microspheres comprise a decline in NPs but increased nanoflakes as shown in Figure 2b. The FESEM and TEM results show the emergence of hollow microspheres (Figure 2e,h). At 12 h (Figure 2c), it was observed that fewer NPs were present, but the nanoflakes became larger and their shell was found to be thinner, with an approximate thickness of 200 nm (Figure 2f,i). The schematic representation of the development of NiSe/MoSe₂/MoO₂ 3D HHM has been depicted in Figure 2j.

The synthesized materials were employed for asymmetric super-capacitor (ASC) applications, achieving a high specific capacitance of 1061 F·g⁻¹ at a current density of 2 A·g⁻¹. They also revealed excellent cycling stability, retaining 93.9% of their initial capacitance after 10,000 cycles, alongside an energy density of 48.1 Wh·kg⁻¹ at a power density of 428 W·kg⁻¹. The superior electrochemical activity is attributed to the large specific surface area and well-developed mesoporous structure, which enhance the contact area among the electrolyte and active material while reducing the ion transport path and time. In other reports [33], a hydrothermal approach was adopted for the formation of a distinctive 2D-2D Co(OH)₂-MoSe₂ hybrid nanosheets. These nanosheets showcased excellent electrical performance with a specific capacitance of 541.55 F·g⁻¹ at 1 A·g⁻¹ in a three-electrode setup. Impressively, the hybrid material retained 91.4% of its capacitance after 3000 cycles. An ASC fabricated with Co(OH)₂-MoSe₂ hybrid nanosheets and activated carbon is a positive and negative electrode material, which can achieve an energy density of 30.12 Wh·kg⁻¹ at a power density of 985.74 W·kg⁻¹. Furthermore, the ASC device engaged 86.2% of its initial capacitance after 3000 cycles, demonstrating the material’s probable for the application of high-performance energy storage. Also, the sodium-ion capacitors have also gained prominence with the integration of few-layer MoSe₂ nanosheets. In a study by Zhao et al. [34], MoO₂@MoSe₂/rGO was used as an anode material for sodium-ion capacitors. Improved sodium-ion diffusion and electron transfer were primarily ascribed to the synergistic belongings of metallic MoO₂ and graphene. Density functional theory (DFT) simulations and characteristic electrochemical impedance spectroscopy (EIS) analyses further validated the electronic coupling between MoO₂ and MoSe₂ at their interface. The anode material achieved a sodium-ion storage capacity of 394 mAh.g⁻¹ at 3.2 A·g⁻¹ and displayed negligible capacity degradation over 5000 cycles at 5 A·g⁻¹. Upon assembling a sodium-ion capacitor with activated carbon as the counter electrode, it demonstrated an energy density of 51 Wh·kg⁻¹ at 7920 W·kg⁻¹. This dual-interface engineering strategy covers the way of a rational strategy of next-generation composite electrodes for sodium-ion capacitors and batteries. An in situ selenization route was employed to fabricate layered 2H-MoSe₂ nanosheets, which were subsequently evaluated for their electrochemical charge storage properties [35]. Structural and morphological examinations confirmed the effective synthesis of these nanosheets. In a three-electrode cell setup with 2 M KOH electrolyte, the MoSe₂ nanosheets exhibited a specific capacity of 46.22 mAh.g⁻¹ at 2 A·g⁻¹, along with impressive cyclic stability over 2000 charge–discharge cycles. A symmetric supercapacitor constructed with MoSe₂ nanosheets displayed a specific capacitance of 4.1 F·g⁻¹ at 0.5 A·g⁻¹, with capacitance retention reaching 105% after 10,000 cycles. This improvement was likely due to the nanosheet activation after initial cycles and a coulombic efficiency of nearly 100%. Gowrisankar et al. [36] developed Mo- and W-based dichalcogenides for supercapacitor applications. By incorporating 2D reduced graphene oxide (rGO) nanosheets into Mo dichalcogenides via an effective one-pot hydrothermal synthesis way, they achieved a MoSSe/rGO composite with a specific capacitance of 373 F·g⁻¹ at 1 A·g⁻¹. The synergistic contact between the materials, facilitated by electrostatic forces, significantly enhanced cyclic durability and structural robustness, making the composite highly reliable for supercapacitor applications. For energy storage purposes [37], a liquid exfoliation technique was employed to synthesize few-layer MoSe₂ nanosheets. When tested as an electrode material for super-capacitors, these nanosheets delivered a specific capacitance of 15 F·g⁻¹ at 0.1 A·g⁻¹ and maintained 95% efficiency over 12 cycles. The sheet-like morphology provided a supreme electrolyte-accessible surface area, enhancing electrochemical performance. A hydrothermal-assisted chemical blending method was utilized to synthesize a MoSe₂ nanoflower-FeOOH nanorod hybrid composite [38]. The formation of the FeOOH and MoSe₂/FeOOH composite is demonstrated in Figure 3. After physicochemical characterizations, the produced materials were adopted as super-capacitor electrode materials. When integrated into a symmetric super-capacitor configuration, the device displayed a specific capacitance of 132 F·g⁻¹ at 1 A·g⁻¹, with minimal capacitance loss over 3000 cycles. Impressively, the device powered a panel of 42 red LEDs continuously for 10 min, showcasing its practical applicability. Additionally, the device achieved an energy density of 18.3 Wh·kg⁻¹ at a power density of 1174 W·kg⁻¹.

In another work by Tanwar et al. [39], the aging effects of selenium powder were explored for its application in super-capacitors. The schematic graph in Figure 4a shows the formation of a MoSe₂ and activated carbon (MoSe₂/AC) composite, whereas Figure 4b demonstrates the preparation of a super-capacitor electrode. The MoSe₂/AC composite was made via a facile hydrothermal method, and its properties were analyzed using numerous characterization techniques. Among the synthesized composites, M6AC exhibited superior performance, achieving a specific capacitance of 394 F·g⁻¹ at a current density of 1 A·g⁻¹, with energy and power densities of 55 Wh·kg⁻¹ and 845 W·kg⁻¹, respectively. In practical applications, this composite was utilized in a symmetric cell capable of illuminating 26 red LED bulbs connected in parallel.

A Ni_0.85Se/N-MoSe₂ hybrid material was synthesized via the facile hydrothermal method with formamide and water as mixed solvents [40]. The synthesized samples (Ni_0.85Se/N-MoSe₂, Ni_0.85Se, and N-MoSe₂) were used as electrode materials for super-capacitor applications. The cyclic voltammetry (CV) results for Ni_0.85Se/N-MoSe₂, Ni_0.85Se, and N-MoSe₂ at a scan rate of 40 mV/s are shown in Figure 5a. The higher electrochemical activity for Ni_0.85Se/N-MoSe₂ was observed and CV curves of the Ni_0.85Se/N-MoSe₂ at different scan rates were collected as shown in Figure 5b. The synergistic effect and N-doping significantly enhanced energy storage capabilities. The GCD curves of the Ni_0.85Se/N-MoSe₂ at different current densities are exhibited in Figure 5c. It can be seen that higher electrochemical performance was observed at 0.25 A·g⁻¹. In addition, the specific capacity versus current density graph is depicted in Figure 5d. The hybrid achieved a specific capacity of 276.5 C·g⁻¹ at 250 mA·g⁻¹, while an asymmetric super-capacitor fabricated with this material showed a specific capacitance of 58.4 F·g⁻¹ at 500 mA·g⁻¹, an energy density of 20.8 Wh·kg⁻¹, and remarkable cycling stability, retaining performance after 15,000 cycles.

MoSe₂ nanosheets grown on rGO via hydrothermal synthesis displayed excellent structural stability and electrical conductivity, facilitated by synergistic interactions and Na⁺ ion intercalation [41]. This material achieved a specific capacitance of 169.3 F·g⁻¹ at 0.5 A·g⁻¹. A solid-state symmetric supercapacitor assembled from this material delivered an energy density of 4.88 Wh·kg⁻¹ at a power density of 150 W·kg⁻¹, with 83.1% retention after 10,000 cycles.

In a research work proposed by Arulkumar et al. [42], the MoSe₂-MXene hybrid nanostructure was synthesized via a hydrothermal method, as shown in Figure 6. The proposed electrode material was used as super-capacitor material and showed a specific capacitance of 1531.2 F·g⁻¹ at 1 A·g⁻¹. Even at a high current density of 5 A·g⁻¹, it retained 94.1% of its capacitance after 10,000 cycles. The MXene incorporation enhanced conductivity, charge transfer, and active site availability.

Velpandian et al. [43] described the fabrication of three MoSe₂-based materials (MoSe₂-P, MoSe₂-E, and MoSe₂-E/C) by employing a hydrothermal method followed by a subsequent liquid phase exfoliation approach. The authors found that MoSe₂-E/C parades a high specific capacitance of 734 F g⁻¹ (@ 1 A g⁻¹). Layek et al. [44] reported MoSe₂ nanosheets composited with noble metals such as Pt, Ag, and Au, synthesized via hydrothermal techniques. Likewise, the electrical conductivity of the noble metal and large surface area of the MoSe₂ nanosheets drastically modified the reaction kinetics electrode by fully exploring the available active site present on nanosheets. The composite with Au nanoparticles exhibited the best performance, with a specific capacitance of 1338 F·g⁻¹ at 1 A·g⁻¹ and excellent cyclic stability, retaining 95% capacitance after 500 cycles. Selenium-enriched MoSe₂ nanoflowers synthesized via hydrothermal methods showed a specific capacitance of 275 F·g⁻¹ at a scan rate of 10 mV s⁻¹ [45]. With an energy density of 36.72 Wh·kg⁻¹ at 400 W·kg⁻¹, the enrichment of selenium enhanced conductivity and electrochemical performance by increasing active site density. Metal–organic frameworks (MOFs) and polyoxometalates were used to synthesize MoSe₂/(Ni, Co)Se₂ hollow nanostructures through encapsulation and selenization [46]. The resulting electrode material achieved a specific capacity of 359.9 mAh g⁻¹ at 1 A·g⁻¹. An asymmetric supercapacitor fabricated with this material distributed an energy density of 40.3 Wh·kg⁻¹ at 800.9 W·kg⁻¹, benefiting from improved active site exposure and charge storage. The incorporation of MWCNTs into NiSe₂@ MoSe₂ composites synthesized via hydrothermal methods enhanced crystallinity, porosity, and ionic interactions [47]. The composite demonstrated a specific capacity retention of 96% after 1000 cycles. Singal et al. [48] proposed that transition metal borides (TMBs) are promising electrode materials for energy storage applications. The authors synthesized cobalt boride (CoB) and optimized various parameters to study the morphological topographies of the CoB. The CoB nanowires showed a charge storage of 273 F·g⁻¹ at 1 A·g⁻¹. Furthermore, MoSe₂ was engineered and incorporated with graphitic carbon nitride (gCN), as shown in Figure 7. The authors achieved an excellent energy density of 97.44 Wh/kg at 621.3 W/kg with an acceptable retention capacitance of 93% using the CoB||gCN/MoSe₂ system.

A titanium dioxide (TiO₂) nanotube/MoSe₂ composite synthesized via hydrothermal methods displayed performance nearly 10 times better than TiO₂ nanotubes alone, with a capacitance of 239 mF cm⁻² at 1 mA cm⁻², combining electric double-layer and pseudo-capacitive behavior [49]. Huang et al. [50] developed (Ni_xCo_1−x)_0.85Se/N-MoSe₂ hybrids, with the combination of Ni and Co (0.8:0.2) providing the best performance. The material achieved a specific capacity of 397.9 C g⁻¹ at 0.5 A·g⁻¹, and the asymmetric device powered a timer for 24 min, highlighting its practical utility. A Ni₂P/NiSe₂/MoSe₂ hybrid material synthesized via hydrothermal methods exhibited improved interlayer spacing, active site exposure, and electrochemical properties [51]. The hybrid attained a specific capacitance of 607.5 F·g⁻¹ at 0.5 A·g⁻¹, while the fabricated super-capacitor delivered 66.1 F·g⁻¹ at 0.5 A·g⁻¹. The MoSe₂@NiSe₂ hybrid nanostructure (0D/1D), prepared hydrothermally, achieved a high capacitance of 802 F·g⁻¹ with 92.7% retention [52]. The abundant active sites reduced internal resistance, enhancing ionic transport and electrochemical performance. The dual-activation process, through the introduction of oxygen-containing active functional groups, enhances the structural properties of carbon nanotubes (CNTs) while significantly increasing their specific surface area [53]. This leads to the development of activated functional carbon nanotubes (AFCNTs) with augmented pore structures and an abundance of active sites. MoSe₂/AFCNT composites, fabricated by decorating MoSe₂ nanoflowers onto AFCNT via hydrothermal methods, demonstrated excellent energy storage. The composite achieved 335 F·g⁻¹ at 1 A·g⁻¹, and the symmetric super-capacitor exhibited a power density of 1.25 kW·kg⁻¹ and an energy density of 1.39 Wh·kg⁻¹, sufficient to power an electric watch.

The comprehensive studies on MoSe₂-based materials affirm their viability as high-performance electrode materials for super-capacitors. The incorporation of hybrid nanostructures, conductive composites, and novel fabrication techniques has significantly improved their electrochemical performance. MoSe₂-based electrodes exhibit high specific capacitance, excellent cycling stability, and enhanced energy and power densities, making them promising candidates for future energy storage applications. However, challenges such as limited cycling durability, structural degradation, and fabrication costs necessitate further advancements in material design and synthesis techniques. Future research should focus on optimizing electrode architectures, exploring novel dopants, and developing eco-friendly and scalable production methods. By overcoming these issues, MoSe₂-based SCs may contribute significantly to the development of sustainable and efficient energy storage technologies.

Table 1. Electrochemical performance of the reported MoSe₂-based SCs.

Material	Synthesis Method	Electrolyte	Specific Capacitance (F/g)	Current Density (A/g)	Stability	References
MoSe2	Microwave	0.5 H2SO4	257.38	1	95% for 5000 cycles	[31]
NiSe/MoSe2/MoO2	Hydrothermal		1061	2	93.9% for 10,000 cycles	[32]
Co(OH)2-MoSe2	Hydrothermal	6M KOH	541.55	1	91.4% after 3000-cycles	[33]
2H-MoSe2	In situ selenization	2M KOH	46.22 mAh.g−1	2	100% for 10,000 cycles	[35]
MoSSe/rGO	Hydrothermal	6 M KOH	373	1	89.5% for 4600 cycle	[36]
MoSe2	Liquid exfoliation		15	0.1	95% for 12 cycles	[37]
MoSe2/FeOOH	Hydrothermal-assisted chemical blending		132	1	100% for 3000 cycles	[38]
MoSe2/AC (Activated carbon)	Facile hydrothermal	6M KOH	394	1	105.1% for 15,000 cycles	[39]
Ni0.85Se/N-MoSe2	Hydrothermal	4 M KOH	276.5 C·g−1	0.25		[40]
MoSe2-MXene	Hydrothermal	3M KOH	1531.2	1	96% for 10,000 cycles	[42]
MoSe2-Au	Hydrothermal		1338	1	95% for 500 cycles	[44]
Ti/(TiO2) nanotubes/MoSe2	Hydrothermal	0.5 M K2SO4	239 mF cm−2	1 mA cm−2	127% for 1000 cycles	[49]

shows the performance of the reported SCs.

3. Hydrogen Evolution Reactions Using MoSe₂-Based Materials

In the past years, electro-catalytic HER process has been considered as one of utmost hopeful energy technologies. MoSe₂-based materials were reported for HER applications. Burragoni et al. [54] described a one-pot hydrothermal process of flowers like MoSe₂ nanoflakes (NF) for HER applications. The proposed material showed an acceptable current density of 0.02 mA/cm² for HER. Tang et al. [55] stated the development of CoSe₂/MoSe₂ nanospheres by employing the hydrothermal-assisted selenization method, as shown in Figure 8. The synthesized CoSe₂/MoSe₂ nanospheres showed a low overpotential of 168 mV with high stability of more than 12 h.

In another work [56], a carbon-coated MoSe₂/Mo₂CT_x composite (MoSe₂/Mo₂CT_x@C) was fabricated for HER application. The presence of Mo₂CT_x MXene may improve the electrical conductivity of the specified composite and enhanced performance can be observed for HER application. The MoSe₂/Mo₂CT_x@C showed a low overpotential of 108.3 mV at a current density of 10 mA/cm² with long-term cyclic stability in a typical acidic medium. Chouki et al. [57] prepared Mo NPs by the wet chemical method and subsequently used the chemical vapor deposition (CVD) method for the preparation of MoSe₂ thin films. LSV was used for HER activity and an overpotential value of 218 mV was observed at 10 mA/cm² under 0.5 M sulfuric (H₂SO₄) acid. Zhu et al. [58] used silver (Ag)/MoSe₂ composite as electrode material for HER study. The Ag/MoSe₂ shows an overpotential of 187 mV at 10 mA/cm². Li et al. [59] described the electrochemical belongings of the 2H MoSe₂, MoSe₂-CTAB, and MoSe₂-CTAB@F68 for HER studies. Figure 9a shows the LSV graphs of the 2H MoSe₂, MoSe₂-CTAB, and MoSe₂-CTAB@F68, and it can be seen that MoSe₂-CTAB@F68 exhibits better electro-catalytic activities towards HER at 10 mA/cm². This may be attributed to the improved electrochemical properties of the MoSe₂-CTAB@F68. The performance of the MoSe₂-CTAB@F68 is reasonable at 20 wt % Pt/C, as shown in Figure 9a,b. The authors extracted Tafel slops of the 2H MoSe₂, MoSe₂-CTAB, MoSe₂-CTAB@F68, and 20 wt % Pt/C to examine the reaction mechanism for H₂ evolution (Figure 9b). It is understood that a lower Tafel slope suggested the requirement of less additional voltage to improve the current density. The 20 wt. % Pt/C exhibited an excellent low Tafel slope value of 30 mV/dec. However, MoSe₂-CTAB@F68 also exhibited a decent Tafel slope value of 62 mV/dec. Despite this, 2H-MoSe₂ showed a distinctive Tafel slope value of 82 mV/dec.

This revealed that MoSe₂-CTAB@F68 is a promising electrode material for HER. The MoSe₂-CTAB@F68 also demonstrated a low overpotential value compared to the 2H MoSe₂ and MoSe₂-CTAB at different current densities (Figure 9c). The low overpotential of 112, 189, and 240 mV versus RHE was obtained for MoSe₂-CTAB@F68 at 1, 10, and 50 mV/cm², respectively. The double layer capacitance (Cdl) values of the 2H MoSe₂, MoSe₂-CTAB, and MoSe₂-CTAB@F68 were determined as shown in Figure 9d. Electrochemical surface area (ECSA) is crucial for the evaluation of the HER activity of the catalyst. The ECSA of 485 cm², 29 cm², and 171 cm² were observed for MoSe₂-CTAB@F68, 2H MoSe₂, and MoSe₂-CTAB, individually. The EIS graphs of the 2H MoSe₂, MoSe₂-CTAB, and MoSe₂-CTAB@F68 are displayed in Figure 9e, and the equivalent circuit has been displayed in the inset. The observations revealed that MoSe₂-CTAB@F68 has low charge transfer resistance i.e., R_ct compared to the 2H MoSe₂, and MoSe₂-CTAB as shown in Figure 9e. Thus, it is clear that MoSe₂-CTAB@F68 has higher electrical conductivity compared to the 2H MoSe₂ and MoSe₂-CTAB. The stability of the MoSe₂-CTAB@F68 for HER has been displayed in Figure 9f. It is seen that MoSe₂-CTAB@F68 has higher stability up to 2000 cycles. Xiao et al. [60] investigated the theoretical and experimental role of plasma functionalization for HER. Oxygen plasma-treated MoSe₂ was explored for HER and an interesting Tafel slope of 55.2 mV/dec and overpotential of 165 mV at 10 mA/cm² were obtained. In another study [61], the spontaneous formation of the surface electron accumulation, i.e., SEA has appeared in the prepared 2H hexagonal structure of MoSe₂ crystal. Authors found the presence of higher electron concentration in the prepared MoSe₂ compared to the bulk. The SEA was generated due to mechanical exfoliation and deselenization at room temperature. The Se vacancies may be the source for SEA and n-type conductivity and active sites in MoSe₂. The authors observed that SEA conjugated and Se vacancy-based surface defects in the MoSe₂ improved the HER activity, and a low overpotential of 170 mV and a Tafel slope of 60 mV/dec were obtained for 2H MoSe₂. Rahul et al. [62] proposed the electrochemical HER activity of MoSe₂/WSe₂ and reported an overpotential of 275 mV and a Tafel slope of 80 mV/dec. In another study [63], the MoSe₂–Ni(OH)₂ nanocomposite was prepared and its HER activity was checked by the LSV technique. The MoSe₂–Ni(OH)₂ exhibited better electrochemical activity and an interesting Tafel slope value of 54 mV/dec was described. Liu et al. [64] proposed a one-pot hydrothermal synthetic procedure for the formation of a few layered 1T@2H MoSe₂ for HER. The authors observed that 1T@2H MoSe₂ has better HER activity compared to the 2H MoSe₂ and a low overpotential of 118 mV with a small Tafel slope of 65.8 mV/dec.

According to Zhu et al. [65], various catalysts were employed for HER in an alkaline medium. Figure 10a shows the LSV data of the commercial Pt/C and suggests the presence of the lowest overpotential value. Tafel graphs of the various catalysts are shown in Figure 10b, whereas overpotential values of the various catalysts have been exhibited in Figure 10c. It could be seen that CoSe₂-MoSe₂ (1–1)/rGO has relatively better electrochemical activity towards HER, and a low overpotential of 182 mV was obtained at 10 mA/cm². This overpotential value for CoSe₂-MoSe₂ (1–1)/rGO catalyst was superior compared to the other catalysts (CoSe₂/rGO, MoSe₂/rGO, MoSe₂, CoSe₂-MoSe₂ (1–1), and CoSe₂), as shown in Figure 10c. The C_dl values of the various catalysts are summarized in Figure 10d and it was observed that CoSe₂-MoSe₂ (1–1)/rGO has larger Cdl value compared to the other catalysts (CoSe₂/rGO, MoSe₂/rGO, MoSe₂, CoSe₂-MoSe₂ (1–1), and CoSe₂). This reveals that CoSe₂-MoSe₂ (1–1)/rGO has higher ECSA compared to the other catalysts (CoSe₂/rGO, MoSe₂/rGO, MoSe₂, CoSe₂-MoSe₂ (1–1), and CoSe₂). The EIS study revealed the existence of R_ct value of 6.9 Ω, 8.3 Ω, 11.8 Ω, 22.1 Ω, 73.6 Ω, and 124.1 Ω for CoSe₂-MoSe₂ (1–1)/rGO, MoSe₂/rGO, CoSe₂/rGO, CoSe₂-MoSe₂ (1–1), MoSe₂, and CoSe₂, respectively (Figure 10e). Thus, it is clear that CoSe₂-MoSe₂ (1–1)/rGO has high electrical conductivity. The CoSe₂-MoSe₂ (1–1)/rGO showed excellent HER activity and an overpotential of 182 mV at 10 mA/cm² with a Tafel slope of 89 mV/dec were achieved under an alkaline environment. Thus, CoSe₂-MoSe₂ (1–1)/rGO showed a fast electron transfer rate in the representative alkaline solution for HER. The CoSe₂-MoSe₂ (1–1)/rGO also demonstrated excellent stability for 15 h. The stability data are shown in Figure 10f.

According to a previous study [66], MoSe₂/NiSe-1 showed an excellent overpotential value of 30 mV at 10 mA/cm² and stability for 40 h. This may be ascribed to the presence of the synergistic effects in the proposed electrode material. Yang et al. [67] proposed a new Mo@(2H-1T)-MoSe₂ monolithic electrode for HER which demonstrated excellent electrochemical H₂ evolution in acidic and basic medium. The Ce-doped MoSe₂@CNTs displayed an overpotential of 166 mV at 10 mA/cm² under the optimized conditions [68]. N-doped 1T-2H MoSe₂/graphene was also explored as HER material and a low overpotential of 153 mV and Tafel slope of 67 mV/dec was achieved, which is superior to N-MoSe₂ (197 mV; 83 mV/dec) and undoped MoSe₂ (252 mV; 123 mV/dec) [69]. The N-doped 1T-2H MoSe₂/graphene also showed good cyclic stability over 10,000 cycles. It was also found in another study that a low overpotential of 70 mV with a Tafel slope of 39 mV dec⁻¹ can be obtained using Ru-MoSe₂/CMT (carbon microtube) as an electrode material in alkaline conditions (1 M KOH) [70]. According to Li et al. [71], doping may improve the electrochemical performance of MoSe₂ and reported the fabrication of MoSe_2-2xS_2x for HER, which displayed a Tafel slope of 54 mV/dec and an overpotential of 167 mV at 10 mA/cm². Liu et al. [72] prepared a bionic Ni_xSe_y/MoSe₂ coralline-liked structure on 2D nickel foam (NF) for HER. The fabricated electrode showed an overpotential of 76 mV at 10 mA/cm². It was observed that 1T-2H MoSe₂ may enhance the electrical conductivity of single phase MoSe₂, and the presence of multiple phases was authenticated by XPS studies. Salehi et al. [73] also demonstrated the role of the MoSe₂/rGO composite for HER and reported the generation of decent H₂ with a Tafel slope of 49 mV/dec and an overpotential of 271 mV. Luo et al. [74] also proposed the construction of a caterpillar-like 3D graphene nanoscrolls@CNTs (GNS@CNTs) scaffold decorated with Co-doped MoSe₂ towards HER application. The Co-MoSe₂-GNS@CNT shows an overpotential of 113 mV, whereas Kuang et al. [75] reported an overpotential of 25.5 mV and 38.4 mV for Ru/MoSe₂-embedded mesoporous hollow carbon spheres in characteristic acid-and-alkaline media, respectively. Guo et al. [76] stated that metal–organic-framework (MOF)-derived metal-based catalysts may exhibit better electrochemical activity for large-scale commercialization for HER. In this regard, the authors prepared Ni and Mo bimetallic selenide (MoSe₂@NiSe₂) with hollow core–shells. The selenization reaction was carried out to associate MoSe₂ with NiMOF-derived NiSe₂. It was found that spherical clusters of the MoSe₂ may prevent the agglomeration and improved electrochemical activity can be observed. The overpotential of 187 mV and Tafel slope of 71.43 mV/dec were obtained for NiMOF-derived MoSe₂@NiSe₂. The V–WMoSe₂ was fabricated by hydrothermal method and employed towards HER [77]. The obtained results displayed a decent overpotential of 247 mV and a Tafel slope of 70 mV/dec. Dogra et al. [78] reported a decent Tafel slope of 87 mV/dec by utilizing a hydrothermally prepared MoSe₂/ZnO composite. It was observed that the presence of the 1T MoSe₂ phase enhances the catalytic behavior. Alahmadi et al. [79] found that VSe₂/MoSe₂ may be a promising electrode material for HER. Thus, the authors prepared VSe₂/MoSe₂ using a hydrothermal method and applied it as an electro-catalyst for HER and achieved a low onset potential of 330 mV with a Tafel slope of 66 mV/dec. This improved performance might be recognized by the decent electrical conductivity and synergistic interactions in the prepared electro-catalyst. Wang et al. [80] fabricated oxygen-modified 2H-phase MoSe₂ on titanium carbide Mxene (MoSe₂/O@Ti₃C₂T_x), and the formation of the catalyst has been described in Figure 11a.

The catalytic activity of the MoSe₂/O@Ti₃C₂T_x has been displayed in Figure 11b. The MoSe₂/O@Ti₃C₂T_x catalyst displayed an overpotential of 121 mV and a Tafel slope of 82 mV/dec. This excellent performance may ascribed to the synergistic effects and high conducting nature of the MXene. Alshgari et al. [81] proposed the excellent catalytic properties of the Ti₃C₂T_x/MoSe₂ nanoflower (T_x = O, and F surface terminations) composite towards HER. The proposed catalyst demonstrated a low overpotential of 135 mV and a Tafel slope value of 72 mV/dec, which might be accredited to the high electrical conductivity of the composite. In another study, Li et al. [82] used a low-temperature nitrogen plasma strategy and prepared a N-doped 1T-2H MoSe₂/N-carbon paper (CP) which showed a Tafel slope of 54.7 mV/dec and overpotential of 274 mV. It was stated that N doping and the presence of 1T/2H structure of MoSe2 exhibited more active sites and enhanced the electrical conductivity of the N-MoSe₂/NCP-30. Thus, improved electrochemical activity was observed towards HER. Ma et al. [83] also employed Ti₃C₂Tsss_x MXene as a substrate to load the 2H MoSe₂ by using a hydrothermal approach. The synthesized MoSe₂/MXene was further modified with atomically-dispersed ruthenium (Ru) single atoms (RuSAs) to form RuSAs@MoSe₂/MXene. Electrochemical studies showed a decent overpotential of 49 mV and a Tafel slope of 52 mV/dec for RuSAs@MoSe₂/MXene in 0.5 M H₂SO₄. This material was also found stable for 120 h at 10 mA/cm². Kozarenko et al. [84] fabricated mechanically exfoliated MoSe₂ (gMoSe₂) and its composite with graphite (Gr) using a benign approach. The obtained gMoSe₂/Gr was adopted as a catalyst for HER. The LSV results showed a Tafel slope of 40 mV/dec and a potential of −75 V at a current density of 10 mA/cm². The proposed catalyst also had decent stability for 20 h under high current density. A study by Zhu et al. [85] reported a remarkably good overpotential of 147.8 mV for RuSe₂/MoSe₂, which was superior compared to the pristine MoSe₂ (351.8 mV). The interface engineering and presence of synergistic interactions between RuSe₂ and MoSe₂ may improve their electrochemical activity for HER. Qin et al. [86] found that pristine MoSe₂ shows sluggish HER kinetics under an alkaline system which might be owed to the intrinsically inferior electrical conductivity/disappearance of active sites. Therefore, the authors synthesized MOF-derived CoSe/MoSe₂ heterogeneous structure for HER. The electrochemical investigations revealed that MOF-derived CoSe/MoSe₂ displayed an overpotential of 135 mV at 10 mA/cm². Vikraman et al. [87] prepared MoSe₂ and MoS₂ on the Mo foil to improve the HER activity. The prepared catalyst shows an overpotential of 81 mV at a current density of 10 mA/cm² with a Tafel slope of 43 mV/dec. Kumar G et al. [88] used top-down strategies to prepare the silicon (Si) NPs via the mechanical ball milling method. Furthermore, the prepared Si NPs were introduced into the 2D MoSe₂ matrix by using the hydrothermal method. The authors varied the percentage of the Si NPs in the range of 0 to 15%, and 10% Si NPs was found to be an optimized amount. The Si: MoSe₂ exhibited onset low overpotential of 76.23 mV with a Tafel slope of 112.3 mV/dec under the optimized conditions. Zhang et al. [89] introduced NiV-MoSe₂ as a catalyst for HER. The LSV results showed that NiV-MoSe₂ has an overpotential of 74.5 mV at 10 mA/cm² and a Tafel slope of 56.2 mV/dec. It was observed that upgrading in the catalytic activity of theNiV-MoSe₂ was likely attributed to the doping with V and Ni. The intrinsic activity, conductivity and ECSA were improved which further enhanced the H₂ evolution.

In summary, MoSe₂-based materials hold significant potential as efficient electrocatalysts for HER applications. Various structural modifications, including metal doping, heterostructure formation, and defect engineering, have been successfully implemented to enhance their electrochemical performance. The integration of MoSe₂ with highly conductive supports, such as MXene and graphene, has further improved its catalytic activity by reducing charge transfer resistance and increasing the number of active sites. Despite these advancements, challenges remain in achieving performance levels comparable to noble metal catalysts like Pt. Future research should focus on optimizing synthesis methods to control phase composition, defect density, and surface chemistry to maximize catalytic efficiency. Moreover, further studies on the stability and scalability of these materials are crucial for their practical implementation in hydrogen production. Overall, MoSe₂-based electrocatalysts provide a promising and cost-effective alternative for sustainable hydrogen generation, with ongoing research expected to further enhance their efficiency and applicability in renewable energy technologies.

Table 2. Electrochemical performance of the reported MoSe₂-based materials for HER.

Material	Synthesis Method	Electrolyte	Tafel Slope (mV.dec−1)	Overpotential mV (at 10 mA cm−2)	References
MoSe2	Microwave	0.5 M H2SO4	58	110	[31]
MoSSe/rGO	hydrothermal	1 M H2SO4	98	285	[36]
MoSe2/Mo2CTx@C	Hydrothermal	0.5 M H2SO4	70.7	108.3	[56]
MoSe2	CVD	0.5 M H2SO4		218	[57]
Ag/MoSe2-5	Self-assemble	0.5 M H2SO4	80.3	187	[58]
MoSe2-CTAB@F68	Hydrothermal	0.5 M H2SO4	62	189	[59]
MoSe2 nanosheets	Hydrothermal	0.5 M H2SO4	55.2	165	[60]
2 H-MoSe2	Chemical vapor transport	0.5 M H2SO4	60	170	[61]
H2O2 assisted MoSe2/WSe2	Liquid exfoliation	0.5 M H2So4	80	275	[62]
MoSe2–Ni(OH)2	Hydrothermal technique	0.5 M H2So4	54	230	[63]
1T@2H–MoSe2	Hydrothermal	0.5 M H2So4	65.8	118.75	[64]
MoSe2-2xS2x	Hydrothermal	0.5 M H2So4	54	167	[71]
Co-MoSe2-GNS@CNT	Solvothermal	0.5 M H2So4	61	151	[74]
MoSe2/ZnO	Hydrothermal	0.5 M H2So4	87	250	[78]
gMoSe2/Gr(2h)	Ball mill	0.5 M H2SO4	40	75	[84]

displayed electrochemical performance of the reported articles for HER applications.

4. Electrochemical Sensing Applications

MoSe₂-based materials are promising electrode materials for various electrochemical applications. MoSe₂-based materials modified electrodes have been widely used in electrochemical applications. In this section, we described the progress in MoSe₂-based materials for electrochemical sensing applications. 17β-estradiol is one of the common environmental endogenous estrogens and it is known to disrupt the endocrine system and has the potential to have negative impacts on growth, reproduction, and development [90]. 17β-estradiol has poor biodegradability and it can be widespread in the environment. Thus, 17β-estradiol can be accumulated into organisms, and it may influence the physiological processes. Thus, the sensing of 17β-estradiol is of great significance and He et al. [90] prepared carbon aerogel nanosphere (CANS)-modified MoSe₂ by using a hydrothermal treatment. The electrochemical sensor for the determination of 17β-estradiol was developed using CANS/MoSe₂ as a biosensing material. Thus, the authors used aptamer/gold nanoparticles (AuNPs)/MoSe₂-CA/GCE as working electrodes and utilized differential pulse voltammetry (DPV) and cyclic voltammetry (CV) for the sensing of 17β-estradiol. The authors reported a decent limit of detection, e.g., LOD of 2.0 × 10⁻¹³ mol/L with a wide dynamic linear range of 5.0 × 10⁻¹² to 5.0 × 10⁻⁹ mol/L. Diphenylamine (DPA) has a formula of C₁₂H₁₁N and is a well-known organic derivative of aniline. DPA is widely used in various applications such as the food industry (as an inhibitor), but it may cause various hazardous effects on human health such as damage to the red blood cells, eczema, and bladder diseases. In this regard, the monitoring of BPA is important and the fabrication of BPA sensors is of great significance. Sakthivel et al. [91] synthesized europium (Eu)-doped MoSe₂ using hydrothermal treatment. The synthesized EuMoSe₂ was coated on the surface of GCE and its electrochemical activity for the determination of BPA was performed on an electrochemical setup. The CV and DPV outcomes exposed that EuMoSe₂-modified GCE has a decent LOD of 0.008 µM, a linear range of 0.01–243.17 µM, and a sensitivity of 2.32 μA μM⁻¹ cm⁻². The working mechanism for the monitoring of BPA can be seen in Figure 12. The EuMoSe₂-modified GCE also showed good recovery in apple juice samples.

Zhang et al. [92] tested the preparation of Au@Pt dendritic nanorods loaded with amino-functionalized MoSe₂ nanosheets (Au@Pt DNRs/NH₂-MoSe₂ NSs) using novel and benign strategies. The surface morphological characteristics of the synthesized material were characterized by SEM and TEM. Furthermore, the authors deposited Au@Pt DNRs/NH₂-MoSe₂ NSs on the surface of GCE and the electrochemical activity for the determination of alpha-fetoprotein (AFP) was examined via CV and amperometry techniques. The LOD of 3.3 fg/mL and the linear range of 10 fg/mL to 200 ng/mL were obtained for the sensing of AFP via Au@Pt DNRs/NH₂-MoSe₂ NSs-modified GCE. This developed sensor also exhibited good recovery in serum samples which suggested its potential for practical applications. Zang et al. [93] informed the fabrication of an imprinted electrochemical sensor by preparing sulfur(S)-MoSe₂/Au/N,S-doped graphene (NSG)/Au composites (S) for the determination of dopamine (DA). The authors employed prepared S-MoSe₂/NSG/Au/ molecularly imprinted polymers (MIPs) as DA sensors. The DPV method was used for the sensing of DA and the authors attained a decent LOD of 0.02 µM and a linear range of 0.05 µM to 1000 µM. It was found that the prepared DA sensor has excellent selectivity and sensing activity in human blood samples. Meanwhile, the extended use of rifamycin antibiotics like rifampicin (RIF) may have negative effects on the environment and human health. Thus, Ganguly et al. [94] described the creation of a RIF sensor by preparing a MoSe₂-embedded reduced graphene oxide (rGO) functionalized β-cyclodextrin (β-cd) polymer electrode material. The development of the electrode material was confirmed by X-ray diffraction (XRD) method. The XRD studies confirm the foundation of MoSe₂/rGO/β-cd. The prepared MoSe₂/rGO/β-cd was coated on the active surface of the GCE. The constructed MoSe₂/rGO/β-cd/GCE was employed as an RIF sensor, which exhibited an LOD of 28 nM and a linear range of 0.019 to 374.5 µM with an acceptable sensitivity of 11.64 μA μM⁻¹ cm⁻². The MoSe₂/rGO/β-cd/GCE also exhibited excellent sensitivity for real sample studies in urine, fish, industrial water, and human serum samples (Figure 13).

In other reported articles, Pothipor et al. [95] reported the fabrication of cancer antigen 15-3 (CA 15-3) and microRNA-21 (miRNA-21) sensors. The authors employed Au NPs-dye/poly(3-aminobenzylamine)/MoSe₂/graphene oxide electrodes for the determination of CA 15-3 and miRNA-21. The authors obtained LOD at the femtomolar level (1.2 fM) for the sensing of miRNA-21 whereas the LOD of 0.14 U/mL was achieved for CA 15-3. Rao et al. [96] proposed a green step involving the synthesis of kudzu biochar (BC)-decorated MoSe₂ via in situ hydrothermal method. It was observed that BC may significantly enhance the electronic conductivity, cyclic stability and electrochemical active area of MoSe₂. The MoSe₂-BC based electrode was employed as a hesperetin (HP) sensor. The MoSe₂-BC based electrode exhibited an LOD of 2 nM and a wide dynamic linear range of 10 nm to 9.5 µM via DPV. The proposed sensor also demonstrated acceptable recovery in the orange peels extraction sample. The improved LOD may be ascribed due to the enhanced conductivity and electrochemical active area of the MoSe₂-BC-based electrode. Shah et al. [97] observed the construction of an endosulfan (En) sensor. The MoSe₂/GO nanohybrid was coupled with a specific immune-recognition element applied for the sensing of En. The authors achieved an LOD of 7.45 ppt using the DPV method. It is well known that miRNA-155 is a distinctive biomarker for breast cancer. The determination of miRNA-155 is of great significance, and Yan et al. [98] proposed the formation of a flower-like MoSe₂@1T-MoS₂ heterojunction via the hydrothermal method. The formation of MoSe₂@1T-MoS₂ has been described in Figure 14a. The morphology of the MoSe₂@1T-MoS₂ was checked by SEM, and it was suggested, from the obtained results, that MoSe₂@1T-MoS₂ has a flowers-like structure (Figure 14b). The presence of elements, i.e., S, Mo, and Se, was confirmed by EDX mapping with uniform particle distribution (Figure 14c). XRD results authenticated the formation of MoSe₂@1T-MoS₂ as demonstrated in Figure 14d. The authors also employed X-ray photoelectron spectroscopy (XPS) for further characterization as revealed in Figure 14e. The XPS confirmed the presence of Mo, S, and Se elements. The high-resolution XPS scan of Mo3d and S2p are displayed in Figure 14f,g, respectively. Furthermore, the authors employed MoSe₂@1T-MoS₂ as an electrode modifier for the sensing of miRNA-155. The reported sensor confirmed an LOD of 0.34 fM and a linear range of 1 fM to 1 nM.

Heavy metals such as chromium (Cr(VI)) are toxic and it is a challenge to eliminate the heavy metal-ions from the waste water. Mittal et al. [99] synthesized MoSe₂-modified ZIF-67 composite for the reduction in Cr(VI). The authors reported an LOD of 0.01 µM for the determination of Cr(VI) with excellent stability. In a report by Wu et al. [100], platinum (Pt)/MoSe₂ was fabricated for the sensing of hydrogen peroxide (H₂O₂). The presence of Pt may significantly augment the conductivity of the MoSe₂ and improve the electrochemical sensing ability for the determination of H₂O₂. The Pt/MoSe₂ exhibited excellent selectivity for the determination of H₂O₂ with an LOD of 2.56 µM. The proposed H₂O₂ sensor also showed good recovery in rain water, human serum, and tap water. Chlorpyrifos (CPS) is one of the pesticides widely used in the agricultural field. The CPS has toxic and hazardous effects on human health and the environment [101]. Thus, monitoring of CPS is of great significance. The hydrothermal method-assisted chemical reduction approach was used for the preparation of the Au nanocluster (AuNCs)/MoSe₂-Porous carbon (PC) material. The synthesized AuNC-MoSe₂-PC was coated on GCE and explored for the sensing of CPS using CV, linear sweep voltammetry (LSV), and amperometry methods. The authors reported an LOD of 0.15 nM and an ultra-sensitivity of 27.027 μA nM⁻¹ cm⁻² with a linear range of 5 to 185 nM towards the sensing of CPS. This sensor also exhibited decent reusability, reproducibility, long-term stability, and repeatability. The pond, paddy, and se water samples were also used for real sample inquiries and adequate recovery was reported for CPS sensing [101]. Yaiwong et al. [102] synthesized toluidine blue (TB)/porous organic polymer (POP)/2D MoSe₂ for the sensing of aflatoxin B₁ (AFB₁). The fabrication of TB/POP/2D MoSe₂/screen-printed carbon electrode (SPCE) is shown in Figure 15.

The TB/POP/2D MoSe₂/SPCE exhibited an acceptable LOD of 0.40 ng/mL with a linear arrange of 2.5 to 40 ng/mL. This established sensor also offers various rewards such as high selectivity, simplicity, reproducibility, and stability. Moreover, this sensor showed good recovery in corn, rice, and peanut samples. Abid et al. [103] described the preparation of AuNPs-MoSe₂-modified electrodes for the sensing of DA. The AuNPs@MoSe₂/SPCE had an LOD of 0.21 µM with a sensitivity of 2.18 µAµM⁻¹ cm⁻² and a linear range of 3 to 20 µM. Xia et al. [104] stated the fabrication of a mercury (Hg(II)) sensor using Co-doped MoSe₂ as electrode material. The authors adopted the square wave anodic stripping voltammetry (SWASV) method for the sensing of Hg (II). The fabricated electrode showed an LOD of 3.96 nM and a sensitivity of 52.17 μA μM⁻¹. These above results show that MoSe₂-based electrode materials have promising features for electrochemical sensing applications.

MoSe₂-based materials have emerged as highly promising candidates for electrochemical sensing applications due to their excellent conductivity, large surface area, and tunable electronic properties. Various modifications, including doping with metals, incorporation with carbon-based materials, and functionalization with biomolecules, have significantly enhanced their electrochemical performance. These advancements have enabled the sensitive and selective detection of a wide range of analytes, including environmental pollutants, hazardous chemicals, biomolecules, and heavy metals. The reviewed studies demonstrate that MoSe₂-based electrodes exhibit remarkable limits of detection (LOD), broad dynamic ranges, and excellent stability, making them suitable for real-world applications in environmental monitoring, biomedical diagnostics, and food safety. The integration of MoSe₂ with novel nanomaterials such as gold nanoparticles, carbon aergels, and graphene derivatives has further improved sensor performance, allowing for precise and rapid analyte detection.

Table 3. Electrochemical performance of the reported MoSe₂-based sensors.

Material	Synthesis Method	LOD (µM)	Linear Range (µM)	Sensing Analyte	Sensing Technique	References
MoSe2-CA hybrids	Hydrothermal	2.0 × 10−13 M	5.0 × 10−12–5.0 × 10−9 M	17β-estradiol	DPV	[90]
EuMoSe2	Hydrothermal	0.008	0.01–243.17	diphenylamine (DPA)	DPV	[91]
S-MoSe2/NSG/Au/MIPs	Hydrothermal	0.02	0.05–1000	dopamine (DA)	DPV	[93]
MoSe2/rGO/β-cd	Hydrothermal	0.0028	0.019–374.5	Rifampicin (RIF)	DPV	[94]
MoSe2@1T-MoS2	Hydrothermal	3.4 × 10−10 M	1 × 10−9–1 × 10−3 M	miRNA-155	DPV	[98]
MoSe2 @ZIF-67	Stirring at RT	0.01	0.01–500	hexavalent chromium (Cr (VI)	LSV	[99]
Pt/MoSe2 nanomesh	Template and in situ modification	2.56		H2O2	CV	[100]
Au-MoSe2-PC-GCE	Hydrothermal	1.5 × 10−4 M	5 × 10−3 to 185 × 10−1 M	Chlorpyrifos (CPS)	Amperometry	[101]
AuNps@MoSe2/SPCE	Liquid-phase exfoliation	0.21	3–20	DA	LSV	[103]

shows the sensing activity of the MoSe₂-based electrode materials for sensing applications.

Despite these advancements, challenges remain, including large-scale fabrication, long-term stability, and practical deployment in complex matrices. Future research should focus on enhancing sensor reproducibility, improving biocompatibility, and exploring new hybrid materials to further expand the capabilities of MoSe₂-based electrochemical sensors. With continued innovation, these materials hold great potential for revolutionizing electrochemical sensing technologies and addressing critical analytical needs across various domains.

5. Conclusions and Perspective

This review highlights the diverse potential of molybdenum diselenide (MoSe₂) as an advanced electrode material for super-capacitors, hydrogen evolution reactions (HER), and electrochemical sensing applications. MoSe₂ exhibits exceptional properties, including superior electrical conductivity, a tunable bandgap, excellent chemical stability, and a high specific surface area. These attributes, coupled with its layered structure and abundant active sites, render it a highly attractive candidate for various electrochemical applications. Its performance in energy storage, energy conversion, and its sensitive detection of biomolecules and pollutants underscores its versatility and significance in these fields. Despite these advantages, several challenges impede the full exploitation of MoSe₂’s capabilities. Key issues include the need to optimize its structural stability, enhance its intrinsic activity, and develop scalable production processes for practical applications. Advances in defect engineering, heterostructure development, and surface modification have shown promise in addressing these limitations. Furthermore, combining MoSe₂ with complementary nanomaterials and leveraging emerging technologies such as 3D printing and artificial intelligence for material design hold significant potential for driving performance improvements.

(1) Designing cost-effective, sustainable, and scalable methods to synthesize MoSe₂ with controlled morphology and high purity.

(2) Utilizing in situ and operando characterization techniques to uncover detailed electrochemical mechanisms and pinpoint performance bottlenecks.

(3) Investigating the synergistic integration of MoSe₂ with other two-dimensional materials, metal oxides, or carbon-based systems to enhance its functionality and broaden its application scope.

(4) Conducting comprehensive stability studies under diverse operating conditions to ensure robustness and practicality for real-world use.

(5) Customizing the properties of MoSe₂ for specific applications, such as high-energy-density super-capacitors, efficient HER electrocatalysts, and ultrasensitive sensors and biosensors.

The convergence of materials engineering, computational modeling, and innovative fabrication techniques presents exciting opportunities to overcome existing challenges. With sustained research efforts and collaborative initiatives, MoSe₂ is well positioned to contribute expressively to expanding sustainable energy technologies and advanced sensing systems.