Search Results (199)

Photoelectrochemical (PEC) energy conversion is a promising approach for solar-to-chemical fuel production, but its practical performance is limited by insufficient visible-light utilization and charge-carrier recombination. Here, poly(3,4-ethylenedioxythiophene) (PEDOT)-centered TiO₂ hybrid electrodes were prepared by electropolymerizing PEDOT on FTO substrates, followed by electrochemical doping/dedoping treatment and coating with commercial TiO₂ as a model oxide semiconductor. SEM, EDS, and LIBS analyses confirmed the successful deposition of TiO₂ onto PEDOT-based films. Four-probe measurements showed that electrochemical doping reduced the apparent resistance of PEDOT-based electrodes, while UV–vis spectroscopy revealed enhanced long-wavelength absorption for doped PEDOT-containing films. PEC measurements using TiO₂, PEDOT, and TiO₂–PEDOT electrodes showed that PEDOT-containing electrodes exhibited much stronger photoresponses than commercial TiO₂ alone under both HER- and OER-relevant conditions. The TiO₂–PEDOT electrode showed stable photocurrent responses under chopped illumination and retained photoresponse under illumination transmitted through a 410 nm UV-cut filter, supporting the primary role of PEDOT in visible-light utilization. Long-term chronoamperometry further showed that TiO₂–PEDOT retained approximately 99.0% of its cathodic current under HER-relevant conditions and 91.9% of its anodic current under OER-relevant conditions after 5200 s of continuous illumination. The improved response of TiO₂–PEDOT compared with PEDOT alone suggests that TiO₂/PEDOT physical contact may assist interfacial charge separation and transport. These findings demonstrate that PEDOT-centered metal oxide/conducting polymer hybrids provide a useful model platform for visible-light-responsive PEC energy-conversion applications. Full article

Two-dimensional (2D) semiconductors have attracted significant attention for their potential in low-power and high-performance electronic applications. Among these, bismuth oxysulfide (Bi₂O₂S) has recently emerged as a candidate owing to its wide bandgap, low effective electron mass, and environmental stability. This review summarizes the synthesis strategies and device applications of 2D Bi₂O₂S. It systematically analyzes recent advancements in synthesis methodologies, ranging from scalable solution-based synthesis to back-end-of-line compatible, low-temperature metal–organic chemical vapor deposition. Furthermore, defect engineering, particularly through oxygen-vacancy control and doping, is discussed as a strategy to modulate the electronic band structure, enhance broadband nonlinear optical properties, and accelerate the photocarrier relaxation kinetics of 2D Bi₂O₂S. These tunable characteristics have enabled 2D Bi₂O₂S to be employed in electronic and optoelectronic devices. The review, therefore, discusses recent developments in device applications of Bi₂O₂S, including field-effect transistors, broadband photodetectors, and flexible photoelectrochemical sensors. Finally, the remaining challenges, such as wafer-scale single-crystal growth and reliable p-type doping, and future research directions are discussed for integrating Bi₂O₂S into three-dimensional integrated circuits and neuromorphic computing. Full article

Copper oxide (CuO) is a narrow-bandgap p-type semiconductor promising for visible-light photocatalysis, yet it suffers from rapid charge recombination and low carrier transfer efficiency. In this study, two distinct CuO photocatalysts were fabricated via different routes: two-dimensional CuO nanosheets derived from annealing a CuBDC metal–organic framework (MOF) precursor, and oriented one-dimensional CuO nanoflower arrays prepared by electrochemical deposition, followed by annealing. The crystal structure, morphology, optical absorption, and photoelectrochemical properties were systematically characterized by XRD, SEM, XPS, UV-Vis spectroscopy, transient photocurrent response, EIS, and PL spectroscopy. The CuO nanoflower thin film exhibits a broad visible-light absorption, a markedly higher photocurrent density (42.25 μA cm⁻²), and lower charge-transfer resistance compared to CuO nanosheets. When evaluated for visible-light photocatalytic degradation of methylene blue (MB), rhodamine B (RhB), and malachite green (MG), the CuO thin film completely degraded MB within 15 min, with an apparent rate constant of 20.15 h⁻¹—approximately three times that of CuO nanosheets. It also showed 1.2- and 1.28-fold higher activity for RhB and MG, respectively. The enhanced performance is attributed to the oriented nanoflower architecture that provides continuous charge transport pathways, suppresses carrier recombination, and extends light propagation via multiple reflections. This work demonstrates that microstructural engineering is an effective strategy to overcome the intrinsic limitations of CuO photocatalysts for wastewater treatment. Full article

Substantial advances have been made since the 1970s in reducing the environmental impacts of ammonia production. Renewable-driven electrochemical synthesis offers a promising pathway to decarbonize ammonia production. This review examines an integrated route in which hydrogen is generated photoelectrochemically under concentrated solar irradiation and subsequently used in electrochemical ammonia synthesis. Photoelectrochemical cells are fabricated by electrostatically depositing photosensitive particles onto cathodes to enhance light-driven hydrogen production. Hydrogen production rates and ammonia yield depend strongly on temperature and electrolyte composition. The synthesized hydrogen is fed into a molten salt electrochemical reactor that operates at atmospheric pressure and receives nitrogen from a dedicated supply. This combined solar–electrochemical approach can produce low-carbon ammonia with improved safety and reduced environmental impact, offering a scalable alternative to conventional processes. Full article

This work targets efficient visible-light-driven hydrogen evolution by construction of a dendritic CdS-based photocatalytic system decorated with Pt-Ni bimetallic cocatalysts (CdS@PtNi). The dendritic CdS was synthesized via a hydrothermal method, followed by in situ deposition of Pt and Ni using NaBH₄ chemical reduction, with cocatalyst loading tuned between 2 and 5 wt%. Among them, C@PN4 (4 wt% total metal loading) demonstrated the best performance, with a bandgap of ~2.15 eV. XRD results show that the samples retain the hexagonal CdS phase without significant impurities. SEM/TEM and elemental mapping confirm uniform dispersion of Pt and Ni, forming intimate interfaces with CdS. XPS results reveal positive shifts in S 2p and Cd 3d binding energies, indicating that the bimetallic cocatalyst promotes electron transfer from CdS to the metals and enhances interfacial coupling. Photoelectrochemical analysis shows C@PN4 features enhanced absorption above 500 nm, significantly reduced PL, extended carrier lifetime, higher transient photocurrent, and lower charge-transfer resistance, suggesting greater efficiency in charge separation and transport. Band structure analysis reveals a negative shift of the conduction band to a more reductive potential. In photocatalytic tests, C@PN4 achieves an H₂ yield of 15.6 mmol g⁻¹ over 4 h (3.9 mmol g⁻¹ h⁻¹), with <5% activity loss after four cycles. AQY reaches 0.0483% at 420 nm, with a monochromatic photon-to-hydrogen conversion efficiency (MPH) of up to 2.01%. Mechanistically, the Pt/CdS Schottky junction drives directional electron extraction, while Ni likely synergistically optimizes interfacial electronic distribution and facilitates water activation/dissociation; together, they accelerate surface reaction kinetics and suppress photocorrosion, achieving efficient and stable hydrogen evolution with low noble metal loading. Full article

Black TiO₂-impregnated electrodes were prepared via a modified dip-coating method, using six deposition layers to investigate the influence of the TiO₂ precursor phase (anatase, rutile, and P25) on their structural and optical properties, as well as their photoelectrooxidation performance toward acetaminophen degradation. A reductive thermal treatment under a H₂/Ar atmosphere successfully modified the band gap energy and promoted the formation of oxygen vacancies (Vo) and Ti³⁺ species, as evidenced by UV–Vis diffuse reflectance spectroscopy and photoluminescence analysis. Among the precursor phases, anatase exhibited the most significant band gap reduction, whereas rutile and P25 showed greater structural stability after the reduction process. Photoelectrochemical experiments revealed that the supporting electrolyte plays a dominant role in the degradation process, with significantly higher removal efficiencies observed in chloride medium (0.1 M NaCl) compared with sulfate medium (0.1 M Na₂SO₄) due to the formation of active chlorine species. Among the tested materials, rutile- and P25-derived electrodes showed the highest degradation efficiencies, reaching concentrations (C/C₀) of 0.631 and 0.650, respectively. The results highlight the combined influence of precursor phase, defect structure, and electrolyte composition on the photoelectrooxidation behavior of black TiO₂ electrodes and provide insights for the design of electrochemical systems for pharmaceutical contaminants removal. Full article

The photocatalytic activity of TiO₂ can be increased by incorporating it into a composite with an electron-trapping co-catalyst. MXene can perform this task as an electron-conducting material. In addition to trapping electrons, it also affects the defects in TiO₂ near the interface. To screen for the best photocatalytic performance, three types of composites were prepared: by physical mixing, chemical deposition, and ALD. During characterization, the structural, optical, and photoelectrochemical properties were determined. Photocatalytic activity was examined in suspension (phenol conversion) and on a layer (gas phase ethanol conversion). It was found that the composite containing the lowest proportion of cocatalyst (1 wt.%) had the highest photocatalytic activity. According to the results of photocatalytic activity measured in suspension, the physical mixtures were proven to be more effective than neat TiO₂, with the composites converting approximately the total amount of phenol in ~40 min, while TiO₂ required ~80–90 min to do so under the same conditions. Thus, the electron-trapping role of MXene is clearly demonstrated in suspension applications, which is also confirmed by other characterization methods (photoluminescence, photocurrent density). TiO₂ performed best during ethanol conversion, as it has the highest ethanol adsorption capacity (33.41%). During ethanol conversion tests, the MXene electron-trapping property was most effectively demonstrated in composites formed using the ALD method. Full article

A ternary CdS–MoS₂–rGO photocathode was developed to enhance visible light-driven hydrogen evolution through interfacial heterostructure engineering. The composite was fabricated via a solution-based deposition method followed by thermal conversion, resulting in crystalline CdS and MoS₂ phases that were uniformly integrated within a conductive reduced graphene oxide (rGO) framework. Structural and surface analyses (XRD and XPS) confirmed the coexistence of Cd²⁺, Mo⁴⁺, and S²⁻ chemical states without detectable secondary phases. Photoelectrochemical measurements revealed that the ternary architecture significantly improves charge separation efficiency and interfacial charge-transfer kinetics compared to binary and single-component films. The CdS–MoS₂–rGO photocathode exhibited the highest photocurrent density, reduced charge-transfer resistance, and favorable Tafel slope under visible-light irradiation (0.25 sun, neutral electrolyte). Gas chromatography measurements verified that these electrochemical enhancements translate into increased hydrogen production rates, following the trend: CdS–MoS₂–rGO > CdS–rGO > MoS₂–rGO >> rGO. Applied bias photon-to-current efficiency (ABPE) analysis further confirmed improved photon utilization efficiency in the ternary system. The enhanced performance is attributed to synergistic integration of CdS (light harvesting), rGO (rapid electron transport), and MoS₂ (catalytic edge sites), which suppresses recombination and accelerates proton reduction kinetics. These findings demonstrate that rational multi-component heterostructure design is an effective strategy for improving hydrogen evolution rate under mild operating conditions. Full article

The photoelectrochemical splitting (PEC) of water provides a direct route to converting solar energy into storable chemical fuels. When illuminated, a semiconductor photoelectrode can absorb light and generate electron-hole pairs, which participate in interfacial redox reactions at the semiconductor-electrolyte junction. Therefore, to achieve high-performance PEC, photoelectrodes with optimized optical absorption and charge have been explored. This review analyzes recent fabrication strategies used to design photoelectrodes for the PEC dissociation of water. Physical fabrication techniques, including pulsed laser deposition, magnetron sputtering, and physical vapor deposition, allow for precise control of film thickness, crystallinity, and defect density, critical parameters for efficient charge transport. Typically, in physical methods, reported photocurrent densities span from ~10⁻² to 10¹ mAcm⁻², depending on the semiconductor material, nanostructure design, and interfacial engineering strategies. Chemical synthesis methods, such as hydrothermal growth, successive ion layer adsorption and reaction, and microemulsion techniques, provide greater compositional flexibility and enable controlled doping, surface functionalization, and the formation of nanostructured morphologies. Finally, hybrid fabrication strategies integrate physical and chemical processes within a single synthesis framework to combine structural precision with compositional tuning capabilities. These approaches enable the development of advanced architecture such as heterojunctions, core–shell nanostructures, and catalyst-modified interfaces, which enhance light absorption and optimize interfacial transfer. Furthermore, theoretical and computational tools are here analyzed as complementary approaches that guide the rational design and optimization of photoelectrochemical materials and devices. Full article

In this study, enhancement- and depletion-mode (E- and D-mode) GaN-based 120 nm-wide fin-gated multiple nanochannel metal–oxide–semiconductor high-electron-mobility transistors (MOS-HEMTs) were manufactured on the epitaxial Al_0.83In_0.17N/GaN/Al_0.18Ga_0.82N/GaN two-dimensional electron gas (2DEG) channel layers grown on Si substrates using a metal-organic chemical vapor deposition system. The oxide layer grown directly by the photoelectrochemical oxidation method was used as the gate oxide layer in D-mode MOS-HEMTs. Furthermore, E-mode MOS-HEMTs used ferroelectric stacked LiNbO₃/HfO₂/Al₂O₃ layers as the gate oxide layers. The 120 nm-wide multiple nanochannels and various-length source field plates (SFPs) were fabricated and incorporated into monolithic complementary MOS-HEMTs (CMOS-HEMTs) consisting of D- and E-mode MOS-HEMTs. The resulting monolithic unskewed inverter was achieved by modulating the drain-source current of the D-mode MOS-HEMTs. The noise low margin of 2.03 V and noise high margin of 2.10 V of the unskewed monolithic inverter were obtained. From the dynamic experimental results, the rising time and falling time of the unskewed monolithic inverter were 4.9 μs and 3.2 μs, respectively. The breakdown voltage could be improved by incorporating an SFP. When the SFP edge was located at the center between the gate electrode and the drain electrode, the maximum breakdown voltage of 855 V was obtained. Full article

Photoelectrochemical (PEC) water splitting offers a sustainable route for solar-to-hydrogen conversion, yet its large-scale deployment is often hindered by energy-intensive and costly fabrication processes for semiconductor photoelectrodes. Electrodeposition provides an attractive alternative owing to its solution-based, low-temperature, and scalable nature; however, the relationship between electrochemical deposition parameters and photoelectrode functionality remains insufficiently understood. Herein, we systematically investigate system-level control in electrodeposition for photoelectrode synthesis using BiVO₄ photoanodes and CuO/Cu₂O photocathodes as model systems. By modulating deposition potential, current density, and electrical control modes, we elucidate how interfacial ion dynamics and growth kinetics govern film morphology, phase evolution, and PEC performance. DC electrodeposition establishes a baseline structure–performance relationship governed by precursor concentration and current density, while pulsed operation enables decoupling of nucleation and growth, leading to refined nanostructures and enhanced photocurrent responses. Further incorporation of reverse-pulsed potentials provides dynamic interfacial reset, enabling precise control over porosity and grain connectivity. The optimized BiVO₄ photoanodes fabricated under tailored reverse-pulsed conditions exhibit improved photocurrent density compared to continuously deposited counterparts. The insights presented here provide practical guidelines for rationally engineering high-performance, scalable, and environmentally benign photoelectrodes for PEC water splitting. Full article

The transition to clean and renewable energy sources is of prime importance in addressing environmental challenges related to the consumption of fossil fuels. Hydrogen, being a clean fuel with a high energy density, has huge potential, especially when it can be obtained through solar-driven PEC water splitting. Herein, $Mo{S}_2$ photocatalysts were synthesized by sulfurizing $Mo{O}_3$ thin films, using a CVD technique. The deposited $Mo{O}_3$ films by thermal evaporation at 450 °C were further sulfurized at 500 °C, 550 °C, and 600 °C. XRD results confirmed the successful conversion of $Mo{O}_3$ into $Mo{S}_2$. The optical properties showed a bandgap reduction from 2.50 eV to 1.30 eV, which leads to better absorption of light in the visible region.The photoelectrochemical experiment shows that the S-$Mo{O}_3$-600 °C thin film has the best performance, and the solar-to-hydrogen conversion efficiency reaches 0.11385% at an applied bias of 1.0 V versus Ag/AgCl, which is about 189 times higher than that of the pristine $Mo{O}_3$ thin film. Full article

In this work, we demonstrate the fabrication of gold-decorated silicon column array (Au/SiCAs) photoanodes for photoelectrochemical (PEC) nitrite detection. The SiCAs were synthesized on n-type silicon substrates via photolithography and anisotropic etching, after which Au nanoparticles were deposited by magnetron sputtering. The Au/SiCAs photoanodes exhibited a pronounced PEC photocurrent response under the simulated solar irradiation. For nitrite determination, the sensor achieved two broad linear ranges (10–500 μM and 2000–10,000 μM) with corresponding sensitivities of 0.25 and 0.33 μA·μM⁻¹·cm⁻², along with a detection limit of 0.25 μM (S/N = 3). Moreover, the sensor exhibited excellent selectivity, remarkable stability, and facile fabrication. Successful detection in real sample confirms its potential for practical applications. This study proposes a novel approach for precise and reliable PEC-based nitrite analysis. Full article

A well-defined heterojunction and tailored interface of the photocathode are desired to facilitate the efficient separation and transfer of photogenerated charge carriers for photoelectrochemical (PEC) hydrogen generation. Herein, optimized Z-scheme heterojunction (denoted as F-COF/TiO₂) photoelectrodes were designed and fabricated by solvothermally growing a F-substituted imine-linked covalent organic framework (F-COF) from 1,3,5-tris(3-fluoro-4-formylphenyl)benzene and 1,4-diaminobenzene on the surface of anodized TiO₂ nanotubes for enhanced PEC hydrogen evolution. The F-COF/TiO₂ heterojunction with photo-deposited Pt species as cocatalysts (Pt@F-COF/TiO₂) revealed higher cathodic photocurrent density, decreased interfacial resistance, and improved onset potential due to the improved charge separation and transfer efficiency at the interface. Both the internal electric field between F-COF and TiO₂, as well as the enhanced photophysical nature of F-COF films, contributed to the efficient interfacial charge separation and transfer. The photo-deposited Pt species and applied bias voltage also demonstrated a synergetic effect on facilitating charge separation and transfer for hydrogen production. The Pt@F-COF/TiO₂ photoelectrode featured an improved PEC hydrogen evolution rate under AM 1.5G simulated sunlight irradiation and a durable PEC hydrogen evolution performance. This study provides valuable insights into the design of heterojunction-based photoelectrodes for efficient solar-driven hydrogen production for sustainable energy applications. Full article

In this study, we have investigated heterostructural TiO₂/BiVO₄ anodes to determine the effect of the amount and form of BiVO₄ nanoparticles on TiO₂ on the response of photoanodes under UV and visible illumination. BiVO₄ nanopowders were prepared and annealed at temperatures ranging from 200 to 500 °C. Structural and optical characterization indicates that as the annealing temperature is increased, a phase transition from a weakly ordered to a dominant monoclinic BiVO₄ phase is observed, which is accompanied by an increase in visible light absorption. Subsequently, the most crystalline powder was utilized to deposit BiVO₄ on nanostructured TiO₂ either as a compact overlayer (drop-casting) or as a progressively grown nanoparticle (TiO₂@S series) in the successive ionic layer adsorption and reaction process (SILAR). Photoelectrochemical measurements were performed, revealing a morphology-dependent photocurrent response under UV and visible illumination. A further increase in the number of cycles systematically increases the photocurrent in the visible light range while limiting the response to UV radiation. The TiO₂@d photoanode demonstrates the highest relative activity within the visible range; however, it also generates the lowest absolute photocurrent, indicating the presence of significant transport and recombination losses within the thick BiVO₄ layer. The results demonstrate that the presence of BiVO₄ nanoparticles on TiO₂ exerts a substantial influence on the separation of charge between semiconductors and the synergistic utilization of photons from the UV and visible ranges. This research yielded a proposed scheme of mutual band arrangement and charge carrier transfer mechanism in TiO₂@BiVO₄ heterostructures. Full article