Search Results (161)

The global energy transition and the implementation of carbon capture, utilization, and storage (CCUS) strategies require energy-efficient and scalable CO₂ separation technologies. Mixed-matrix membranes (MMMs), combining polymer matrices with functional inorganic or hybrid nanofillers, have emerged as advanced separation platforms capable of surpassing the conventional permeability–selectivity trade-off observed in neat polymer membranes. This review critically evaluates recent developments in modern hybrid membranes for CO₂ separation from synthetic and industrial gas mixtures, including CO₂/N₂ (flue gas), CO₂/CH₄ (natural gas and biogas upgrading), and syngas systems. Particular emphasis is placed on MMMs incorporating covalent organic frameworks (COFs), metal–organic frameworks (MOFs), graphene oxide (GO), MXenes, transition metal dichalcogenides (TMDs), carbon nanotubes (CNTs), g-C₃N₄, layered double hydroxides (LDH), zeolites, metal oxides, and magnetic nanoparticles. Reported performance ranges include CO₂ permeability (P_CO2) typically between 100 and 800 Barrer, CO₂/N₂ selectivity up to 319, and CO₂/CH₄ selectivity up to 249, depending on filler chemistry, loading, and interfacial compatibility. The mechanisms governing gas transport—molecular sieving, selective adsorption, facilitated transport, and diffusion-pathway engineering—are systematically discussed. Key challenges addressed include filler dispersion, polymer–filler interfacial defects, physical aging, moisture sensitivity, oxidation (particularly in MXenes), and scalability toward industrial membrane modules. Future perspectives focus on sub-nanometer pore engineering, surface functionalization to enhance CO₂ affinity, controlled alignment of 2D nanosheets to promote directional transport, multifunctional core–shell and hollow structures, and the integration of computational modeling and machine learning for accelerated material design. Modern hybrid MMMs are identified as strategically important materials enabling high-efficiency CO₂ separation processes aligned with decarbonization and energy transition objectives. Full article

Photocatalytic H₂O₂ synthesis emerges as a promising green substitute for the energy-intensive anthraquinone process, yet its efficiency is limited by rapid charge recombination and limited surface active sites in bulk polymeric semiconductors. Herein, we report a topology-directed strategy to tailor the interlayer interactions of graphitic carbon nitride (g-C₃N₄), yielding ultrathin nanosheets with optimized electronic structures. The resulting catalyst exhibits an exceptional H₂O₂ production rate of 1.34 mmol g⁻¹ h⁻¹ under visible light, surpassing bulk g-C₃N₄ by a factor of 2.48. Water contact angle measurements confirm the superior hydrophilicity of the engineered nanosheets, facilitating interfacial mass transfer, while in situ FTIR and EPR spectroscopies unravel that the abundant exposed active sites optimize the adsorption configuration of the key *OOH intermediate and promote the generation of •O₂⁻ and •OH radicals. Regarding charge transfer dynamics, in situ EPR trapping experiments and Kelvin probe force microscopy (KPFM) reveal that the attenuated interlayer coupling induces a robust internal electric field, effectively suppressing carrier recombination and prolonging the exciton lifetime by a factor of 1.249. This work establishes a quantitative structure–activity relationship between interlayer engineering and exciton dynamics, offering a reliable protocol for the rational design of high-performance molecular photocatalysts. Full article

Two-dimensional graphitic carbon nitride 2D g-C₃N₄ has the potential for gas sensing as a metal-free semiconductor with a layered structure, high surface area, and tunability of electronic properties. In this context, 2D g-C₃N₄ nanosheets were prepared by the thermal polycondensation of urea followed by ultrasonic exfoliation. X-ray diffraction revealed diffraction peaks corresponding to the (110) and (002) crystallographic planes of g-C₃N₄. Scanning electron microscopy showed a nanosheet structure with a 10-nm crystallite size, while energy-dispersive X-ray spectroscopy demonstrated a uniform distribution of carbon and nitrogen. Ultraviolet–visible absorption spectroscopy revealed a band gap of 2.8 eV. Gas sensing measurements exhibited an increase in response to isopropanol and ethanol as the operating temperature and gas concentration increased. Impedance spectroscopy provided additional insight into the sensing mechanism. Observed depressed semicircles in Nyquist plots were fitted with a charge transfer resistance R_ct in parallel with a constant phase element model. The charge transfer resistance R_ct fell systematically with isopropanol exposure, confirming the crucial role of adsorption-induced electron transfer in the gas sensing response. Full article

Transition-metal dichalcogenides have emerged as promising non-noble-metal electrocatalysts for efficient hydrogen production through the hydrogen evolution reaction (HER). In this work, we fabricated the graphitic carbon nitride-decorated cobalt diselenide (gC₃N₄-CoSe₂) nanocomposites via the facile hydrothermal method. The prepared gC₃N₄-CoSe₂ nanocomposites displayed an interconnected and aggregated morphology of gC₃N₄-decorated CoSe₂ nanoparticles with offering large surface area of 82 m²/g. The gC₃N₄-CoSe₂ nanocomposites exhibited excellent HER activity with a low overpotential (141 mV) and tiny Tafel slope (62 mV/dec) with excellent durability for 100 h at 10 mA/cm² in an alkaline electrolyte. These outstanding HER performances of gC₃N₄-CoSe₂ can be ascribed to the synergistic interaction between the electrochemically active porous CoSe₂ nanoparticles and the highly conductive gC₃N₄ nanosheets. These results indicate that the gC₃N₄-CoSe₂ nanocomposites hold promising and efficient HER electrocatalysts for sustainable green hydrogen production. Full article

The photocatalytic reduction of CO₂ in aqueous media offers a sustainable route for solar-to-fuel conversion, yet remains challenged by CO₂’s thermodynamic stability and kinetic inertness, low solubility, and competitive hydrogen evolution. Here, we investigate the interplay between ionic liquids (ILs), photocatalyst supports, and additive composition in directing product selectivity among CO, CH₄, and H₂. Using imidazolium acetate as a benchmark, we demonstrate that ILs not only pre-activate CO₂ but can also undergo decomposition pathways under illumination, notably Kolbe-type reactions leading to methane formation from acetate rather than from CO₂. Comparative studies of Pd-decorated TiO₂ and g-C₃N₄ nanosheets reveal distinct behaviors driven by their interfacial interactions with the imidazolim-based ionic liquid: weak interaction with TiO₂ strongly promotes hydrogen evolution, whereas strong coupling with g-C₃N₄ synergizes with C₁C₄ImOAc to trigger acetate-derived Kolbe reactivity. The systematic evaluation of alternative salts confirms the determinant role of anion basicity and medium-pH-basic anions facilitate CO₂ activation, whereas weakly basic or non-coordinating anions favor water splitting. Overall, these results clarify the dual role of ionic liquids as both CO₂ activators and sacrificial agents, and highlight design principles for improving product selectivity and efficiency in aqueous CO₂ photoreduction systems. Full article

Highly permeable and selective membranes are crucial for energy-efficient gas separation. Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) has attracted significant attention due to its unique structural characteristics, including ultra-thin thickness, inherent surface porosity, and abundant amine groups. However, the interfacial defects caused by poor compatibility between g-C₃N₄ and polymers deteriorate the separation performance of membrane materials. In this study, amino-functionalized g-C₃N₄ nanosheets (CN@PEI) was prepared by a post-synthesis method, then blended with the polymer Pebax to fabricate Pebax/CN@PEI mixed matrix membranes (MMMs). Compared to g-C₃N₄, MMMs with CN@PEI loading of 20 wt% as nanofiller exhibited a CO₂ permeance of 241 Barrer as well as the CO₂/CH₄ and CO₂/N₂ selectivity of 39.7 and 61.2, respectively, at the feed gas pressure of 2 bar, which approaches the 2008 Robeson upper bound and exceeded the 1991 Robeson upper bound. The Pebax/CN@PEI (20) membrane showed robust stability performance over 70 h continuous gas permeability testing, and no significant decline was observed. SEM characterization revealed a uniform dispersion of CN@PEI throughout the Pebax matrix, demonstrating excellent interfacial compatibility between the components. The increased free volume fraction, enhanced solubility, and higher diffusion coefficient demonstrated that the incorporation of CN@PEI nanosheets introduced more CO₂-philic amino groups and disrupted the chain packing of the Pebax matrix, thereby creating additional diffusion channels and facilitating CO₂ transport. Full article

Gallic acid (GA), a polyphenol extensively used in the food, wine, and pharmaceutical industries, is known for its inhibitory effects on soil microbial activity. Photocatalytic degradation offers an environmentally friendly solution for GA removal from water. In this work, graphitic carbon nitride (g-C₃N₄) photocatalysts were synthesized by two methods: thermal exfoliation (CN-E) and supramolecular assembly via hydrothermal processing (HCN-II). Structural analyses by XRD, FTIR, and XPS confirmed the formation of the g-C₃N₄ framework, while SEM revealed that CN-E consisted of folded and curled nanosheets, whereas HCN-II displayed a polyhedral–nanosheet hybrid architecture with internal channels. Both materials achieved approximately 80% GA degradation within 180 min under visible-light irradiation, yet HCN-II exhibited a superior apparent rate constant (k = 0.01156 min⁻¹) compared with CN-E. Radical trapping experiments demonstrated that O₂•⁻ and h⁺ were the primary reactive oxygen species involved, with OH• making a minor contribution. The enhanced performance of HCN-II is attributed to its higher surface area, improved light harvesting, and efficient charge separation derived from supramolecular assembly. These findings highlight the potential of engineered g-C₃N₄ nanostructures as efficient, metal-free photocatalysts for the degradation of recalcitrant organic pollutants in water treatment applications. Full article

Constructing heterojunction photocatalysts with efficient interfacial charge transfer is critical for solar-driven hydrogen evolution. In this study, a highly dispersed MoS₂/g-C₃N₄ composite was successfully synthesized via a stirring-assisted hydrothermal in situ growth strategy. The introduction of stirring during synthesis significantly enhanced the uniform dispersion of MoS₂ nanosheets and exposed abundant edge sites, leading to well-integrated heterojunctions with enhanced interfacial contact. Comprehensive structural and photoelectronic characterizations (XRD, SEM, TEM, EDS mapping, UV–Vis, TRPL, EIS, EPR) confirmed that the composite exhibited improved visible-light absorption, accelerated charge separation, and suppressed recombination. Under simulated solar irradiation with triethanolamine (TEOA) as a sacrificial agent, the optimized 24% MoS₂/g-C₃N₄-S catalyst achieved a high hydrogen evolution rate of 14.33 mmol·g⁻¹·h⁻¹ at a catalyst loading of 3.2 mg, significantly outperforming the unstirred and pristine components, and demonstrating excellent cycling stability. Mechanistic studies revealed that the performance enhancement is attributed to the synergistic effects of Type-II heterojunction formation and edge-site-rich MoS₂ co-catalysis. This work provides a scalable approach for non-noble metal interface engineering and offers insight into the design of efficient and durable photocatalysts for solar hydrogen production. Full article

For future clean and renewable energy technology, designing highly efficient and robust electrocatalysts is of great importance. Particularly, creating efficient bifunctional electrocatalysts capable of effectively catalyzing both hydrogen- and oxygen-evolution reactions (HERs and OERs) is vital for overall water electrolysis. In this study, we employ 2D molybdenum disulfide (MoS₂) nanosheets and pyrolytically fabricated 2D graphitic carbon nitride (gC₃N₄) nanosheets to create 2D gC₃N₄-decorated 2D MoS₂ (2D–2D gC₃N₄–MoS₂) nanocomposites using a facile sonochemical method. The 2D–2D gC₃N₄–MoS₂ nanocomposites show an interconnected and agglomerated structure of 2D gC₃N₄ nanosheets decorated on 2D MoS₂ nanosheets. For water electrolysis, the gC₃N₄–MoS₂ nanocomposites exhibit low overpotentials (OER: 225 mV, HER: 156 mV), small Tafel slope values (OER: 49 mV/dec, HER: 101 mV/dec), and excellent durability (up to 100 h for both OER and HER) at 10 mA/cm² in 1 M KOH. Furthermore, the gC₃N₄–MoS₂ nanocomposites show excellent overall water electrolysis performance with a low full-cell voltage (1.52 V at 10 mA/cm²) and outstanding long-term cell stability. The superb bifunctional activities of the gC₃N₄–MoS₂ nanocomposites are attributed to the synergistic effects of 2D gC₃N₄ (i.e., low charge-transfer resistance) and 2D MoS₂ (i.e., a large electrochemically active surface area). These findings suggest that the 2D–2D gC₃N₄–MoS₂ nanocomposites could serve as excellent bifunctional catalysts for overall water electrolysis. Full article

This study reported covalent organic frameworks (COFs) and their hybrid composites with two-dimensional materials, graphene oxide (GO), graphitic carbon nitride (g-C₃N₄), and boron nitride (BN), to examine their structural, textural, and gas adsorption properties. Material characterization confirmed the crystallinity of COF-1 and the preservation of framework integrity after integrating the 2D nanomaterials. FT-IR spectra exhibited pronounced vibrational fingerprints of imine linkages and validated the functional groups from the COF and the integrated nanomaterials. TEM images revealed the integration of the two components, porous, layered structures with indications of interfacial interactions between COF and 2D nanosheets. Nitrogen adsorption–desorption isotherms revealed the microporous characteristics of the COFs, with hysteresis loops evident, indicating the development of supplementary mesopores at the interface between COF-1 and the 2D materials. The BET surface area of pristine COF-1 was maximal at 437 m²/g, accompanied by significant micropore and Langmuir surface areas of 348 and 1290 m²/g, respectively, offering enhanced average pore widths and hierarchical porous strcuture. CO₂ adsorption tests were investigated showing maximum adsorption capacitiy of 1.47 mmol/g, for COF-1, closely followed by COF@BN at 1.40 mmol/g, underscoring the preserved sorption capabilities of these materials. These findings demonstrate the promise of designed COF-based hybrids for gas capture, separation, and environmental remediation applications. Full article

The use of semiconductors for photocatalytic degradation of organic pollutants has garnered considerable attention as a promising solution to environmental challenges. Compared to TiO₂, BiPO₄ exhibits superior photocatalytic activity. However, its large band gap restricts its light absorption to the UV region. One effective technique for extending BiPO₄’s absorption wavelength into the visible spectrum is the construction of the heterostructure. This study aimed to synthesize monodisperse BiPO₄ nanorods via a solvothermal approach and fabricate BiPO₄/g-C₃N₄ heterojunctions with varying loadings through in situ deposition. Tetracyclines were employed as the target pollutant to evaluate the photocatalytic performance and stability of the prepared materials. The results indicated that 5 wt% of composite exhibited better photocatalytic performance than single catalysts, which showed the highest photodegradation efficiency of approximately 98% for tetracyclines. The prepared bi-photocatalyst presented favorable stability under sunlight irradiation, the photocatalytic activity of which remained almost unchanged after four cycles. The enhanced photocatalytic activity was attributed to the synergistic effect. Additionally, the possible degradation mechanism was elucidated utilizing the semiconductor energy band theory. Overall, this work presents new perspectives on synthesizing innovative and efficient visible-light-driven photocatalysts. It also offers a mechanistic analysis approach by integrating theoretical calculations with experimental observations. Full article

Owing to global energy demands and climate change resulting from fossil fuel use, technologies capable of converting greenhouse gases into renewable energy resources are needed. One such technology is photocatalytic CO₂ reduction, which utilises solar energy to transform CO₂ into value-added hydrocarbons. However, the application of photocatalytic CO₂ reduction is limited by the inefficiency of existing photocatalysts. In this study, we developed a nitrogen-deficient g-C₃N₄-confined PtCu dual-atom catalyst (PtCu/V_N-C₃N₄) for photocatalytic CO₂ reduction. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomic-level anchoring of PtCu pairs onto the nitrogen-vacancy-rich g-C₃N₄ nanosheets. The optimised PtCu/V_N-C₃N₄ exhibited superior photocatalytic performance, with CO and CH₄ evolution rates of 13.3 µmol/g/h and 2.5 µmol/g/h, respectively, under visible-light irradiation. Mechanistic investigations revealed that CO₂ molecules were preferentially adsorbed onto the PtCu dual sites, initiating a stepwise reduction pathway. In situ diffuse reflectance infrared Fourier-transform spectroscopy identified the formation of a key intermediate (HCOO*), whereas interfacial wettability studies demonstrated efficient H₂O adsorption on PtCu sites, providing essential proton sources for CO₂ protonation. Photoelectrochemical characterisation further confirmed the enhanced charge-transfer kinetics in PtCu/V_N-C₃N₄, which were attributed to the synergistic interplay between the nitrogen vacancies and dual-atom sites. Notably, the dual-active-site architecture minimised the competitive adsorption between CO₂ and H₂O molecules, thereby optimising the surface reaction pathways. This study establishes a rational strategy for designing atomically precise dual-atom catalysts through defect engineering, achieving concurrent improvements in activity, selectivity, and charge carrier utilisation for solar-driven CO₂ conversion. Full article

In this study, Bi₂MoO₆ nanoflowers with different molybdenum sources were in situ grown on the surface of g-C₃N₄ nanosheets (OCN) by a simple one-step solvothermal method. The effects of doping and different molybdenum sources on the photocatalytic degradation and bactericidal activity of Bi₂MoO₆/OCN were discussed. Among them, the solvothermal preparation of P-Bi₂MoO₆/OCN using phosphomolybdic acid as molybdenum source can make up for the shortcomings caused by the destruction of OCN structure by generating more lattice defects to promote charge separation and constructing Lewis acid/base sites to effectively improve the photocatalytic performance. In addition, by adding phosphoric acid to increase the P-doped content, more exposed alkaline active sites are induced on the surface of P-Bi₂MoO₆/OCN, as well as larger specific surface area and charge transfer efficiency, which further improve the photocatalytic performance. Finally, the optimized 16P-Bi₂MoO₆/OCN showed a degradation rate of 99.7% for 20 mg/L rhodamine B (RhB) within 80 min under visible light, and the antibacterial rates against E. coli, S. aureus and P. aeruginosa within 300 min were 99.58%, 98.20% and 97.48%, respectively. This study provides a reference for optimizing the synthesis of environmentally friendly, solar-responsive, photocatalytic sterilization materials from the perspective of preparation, raw materials and structure. Full article

In this work, we developed a highly sensitive and reproducible electrochemiluminescent sensor based on a heterostructure of cadmium selenide quantum dots capped with 3-mercaptopropionic acid (MPA) + 3-morpholinoethanesulfonic acid (MES) (QDs CdSe) and carbon nitride nanosheets (g-C₃N₄) for the detection of H₂O₂ in lyophilized serum samples. To enhance the sensor sensitivity, g-C₃N₄ nanosheets were utilized as a platform to immobilize the QDs CdSe. An exhaustive characterization of the heterostructure was conducted, elucidating the interaction mechanism between QDs CdSe and g-C₃N₄. It was revealed that g-C₃N₄ acts as a hole (h⁺) donor, while QDs CdSe act as energy acceptors in a resonance energy transfer process, with the electrochemiluminescence emission originating from the QDs CdSe. The electrochemiluminescence intensity decreases in the presence of H₂O₂ due to the deactivation of the excited states of the QDs CdSe. This electrochemiluminescent sensor demonstrates exceptional performance for detecting H₂O₂ in aqueous systems, achieving a remarkably low limit of detection (LOD) of 1.81 nM, which is more sensitive than most reported sensors to detect H₂O₂. The applicability of the sensor was successfully tested where sub-µM levels of H₂O₂ were accurately quantified. These results highlight the potential of this electrochemiluminescent sensor as a reliable and pre-treatment-free tool for H₂O₂ detection in biochemical studies and human health applications. Full article

With the annual increase in carbon emissions and the warming of the global temperature, it is imperative to accelerate the construction of a green, low-carbon, circular economic system. The photocatalytic reduction of CO₂ can convert the emitted CO₂ into valuable carbonaceous products, which is of great significance for alleviating the global CO₂ emission problem. In this study, the literature on the “photocatalytic reduction of CO₂” from two Chinese and foreign databases was used as the analysis sample. From the perspective of net present value, nitride-based catalysts were selected as the research object. An in-depth analysis of the costs and economic benefits of the nitride-based photocatalytic reduction of CO₂ was carried out, considering four factors: catalyst efficiency, light conditions, discount rate, and depreciation period. The analysis results show that with a project duration of 10 years and a discount rate of 10%, the net present values of all the catalysts are negative, indicating that from an economic perspective, investment projects using general catalysts to reduce CO₂ are not feasible under current conditions. However, it is worth noting that when the light conditions are changed and sunlight is used as the light source, the net present values corresponding to the Ta₃N₅/Bi and NiOx/Ta₃N₅ catalysts have turned positive, showing a certain economic feasibility. When the yield is increased to 2.64 times and 6.15 times of the original values, the net present values corresponding to the T-CN/ZIS (refers to ZnIn₂S₄ (ZIS) nanosheets grown in situ on tubular g-C₃N₄ microtubes (T-CNs)) catalyst and the Ta₃N₅ cuboid catalyst turn positive, and only the net present value of the g-C₃N₄/Bi₂O₂[BO₂(OH)] catalyst remains negative. Full article