Sub-5 nm Ultra-Fine FeP Nanodots as Efficient Co-Catalysts Modified Porous g-C3N4 for Precious-Metal-Free Photocatalytic Hydrogen Evolution under Visible Light

Interfacial tuning in FeP/ZnIn2S4 Ohm heterojunction: Enhanced photocatalytic hydrogen production via Zn-P charge bridging

Interfacial regulation is key to photocatalytic performance, yet modulating interfacial charge transfer in heterostructures remains challenging. Herein, a novel nanoflower-like FeP/ZnIn2S4 Ohm heterostructure is first designed, with Zn atoms in ZnIn2S4 (ZIS) acting as potential anchoring sites around P atoms, forming liganded Zn-P bonds. Combining 1D FeP nanowires and 2D ZIS nanosheets enhances the mobility of photogenerated electrons. The synergistic chain-type "electron pickup" mechanism of the Ohm heterojunction coupled with the Zn-P bond speeds up electron transport at the interface. The Ohm heterojunction initiates an internal electric field, creating a driving force to further transfer photogenerated electrons through the Zn-P rapid electron transport channel to FeP, which acts as a reservoir for active sites to release H2. The optimized FeP/ZIS demonstrates a remarkable H2 evolution rate at 4.36 mmol h-1 g-1, 3.6 times that of pristine ZIS. This work provides novel insights into optimizing photocarrier dynamics via interfacial microenvironment modulation.

Addressing the synchronized impact of a novel strontium titanium over copolymerized carbon nitride for proficient solar-driven hydrogen evolution

Currently, novel technologies are highly prerequisite as an outstanding approach in the field of photocatalytic water splitting (PWS). Previous research has shown that copolymerization technology could improve the photocatalytic performance of pristine carbon nitride (CN) more efficiently. As this technology further allows the charge carrier recombination constraints, due to novel monomer-incorporated highly abundant surface-active sites of metals in polymeric carbon nitride-based heterojunction. However, in present study, a novel previously unexplored thiophenedicarboxaldehyde (TAL) conjugated, strontium-titanium (SrTiO3) induced and CN based heterojunction, i.e., SrTiO3/CN-TAL10.0, was prepared for solar-driven hydrogen evolution reaction (HER). This heterojunction effectively enables the proficient isolation of photoinduced charge carriers and enhanced the charge transport over the surface junction, by enhancing the optical absorption range and average lifetime of photogenerated charges. The incorporation of TAL within the structure of CN via copolymerization highly increases the photocatalytic activity, as well as maintaining its photostability performance. The SrTiO3 concentration and the proportion of TAL among CN can be precisely controlled to provide the optimal photocatalytic efficiency with a maximum HER of 285.9 µmol/h under visible light (λ = 420 nm). Based on these results, our optical analysis shows that coupling of SrTiO3 and TAL monomer in the structure of CN considerably reduce the band gap of superior sample from (3.42 to 2.66 eV), thereby, signifying the outstanding photocatalytic performance of SrTiO3/CN-TAL10.0. Thus, this study provide a new guideline in order to develop the multidimensional photocatalysts with proper functioning for sustainable energy conversion and production.

Atomic-level investigation on significance of photoreduced Pt nanoparticles over g-C3 N4 /bimetallic oxide composites

Designing an effective photocatalyst for solar-to-chemical fuel conversion presents significant challenges. Herein, g-C3 N4 nanotubes/CuCo2 O4 (CN-NT-CCO) composites decorated with platinum nanoparticles (Pt NPs) were successfully synthesized by chemical and photochemical reductions. The size distribution and location of Pt NPs on the surface of CN-NT-CCO composites were directly observed by TEM. Extended X-ray absorption fine structure (EXAFS) spectra of Pt L3-edge for the above composite confirmed establishment of Pt-N bonds at an atomic distance of 2.09 Å in the photoreduced Pt-bearing composite, which was shorter than in chemically reduced Pt-bearing composites. This proved the stronger interaction of photoreduced Pt NPs with the CN-NT-CCO composite than chemical reduced one. The H2 evolution performance of the photoreduced (PR) Pt@CN-NT-CCO (2079 μmol h-1  g-1 ) was greater than that of the chemically reduced (CR) Pt@CN-NT-CCO composite (1481 μmol h-1  g-1 ). The abundance of catalytically active sites and transfer of electrons from CN-NT to the Pt NPs to participate in the hydrogen evolution are the primary reasons for the improved performance. Furthermore, electrochemical investigations and band edge locations validated the presence of a Z-scheme heterojunction at the Pt@CN-NT-CCO interface. This work offers unique perspectives on the structure and interface design at the atomic level to fabricate high-performance heterojunction photocatalysts.

V-doped Ni2P nanoparticle grafted g-C3N4 nanosheets for enhanced photocatalytic hydrogen evolution performance under visible light

Exploring low-cost and highly active photocatalysts with noble metal-free cocatalysts is of great significance for photocatalytic hydrogen evolution under simulated sunlight irradiation. In this work, a novel V-doped Ni₂P nanoparticle loaded g-C₃N₄ nanosheet is reported as a highly efficient photocatalyst for H₂ evolution under visible light irradiation. The results demonstrate that the optimized 7.8 wt% V-Ni₂P/g-C₃N₄ photocatalyst exhibits a high hydrogen evolution rate of 271.5 μmol g^-1 h^-1, which is comparable to that of the 1 wt% Pt/g-C₃N₄ photocatalyst (279 μmol g^-1 h^-1), and shows favorable hydrogen evolution stability for five successive runs within 20 h. The remarkable photocatalytic hydrogen evolution performance of V-Ni₂P/g-C₃N₄ is mainly due to the enhanced visible light absorption ability, the facilitated separation of photo-generated electron-hole pairs, the prolonged lifetime of photo-generated carriers and the fast transmission ability of electrons.

Hydroxyl-/Carboxyl-Rich Graphitic Carbon Nitride/Graphene Oxide Composites for Efficient Photodegradation of Reactive Red 195 and Antibacterial Applications

In this work, a protonated graphitic carbon nitride (P-g-C₃N₄)-coated graphene oxide (GO) composite (GO/P-g-C₃N₄) was prepared via wet-chemistry exfoliation, followed by a freeze-drying process. The GO/P-g-C₃N₄ composite was found to have an outstanding photodegradation performance effect on the reactive red 195 (RR195) dye and very strong antibacterial properties. Both the GO structure and the dispersed state of P-g-C₃N₄ were found to play a significant role in enhancing the photocatalytic activity of GO/P-g-C₃N₄. The GO/P-g-C₃N₄ obtained via freeze-drying retained a large number of oxygen-containing groups and showed higher catalytic activity and reusability than the reduced GO (rGO)/g-C₃N₄ obtained via thermal reduction. Characterization of the samples indicates that GO/P-g-C₃N₄ has a higher specific surface area and photocurrent density than rGO/g-C₃N₄; it is likely that these properties lead to the superior photocatalytic activity observed in GO/P-g-C₃N₄. Adsorption energy calculations indicate that O₂ can be readily adsorbed onto the GO surface, which results in stronger oxidizing superoxide anion radicals (^•O₂^-) and holes (h⁺); these active radicals can rapidly degrade RR195 dyes. Moreover, broad-spectrum antibacterial activity (demonstrated against Staphylococcus aureus and Escherichia coli) was observed in the case of the GO/P-g-C₃N₄ composite irradiated with visible light. This work offers new insights into the design of cost-effective g-C₃N₄-based photocatalysts for environmental remediation.

Dual-Mode-Driven Micromotor Based on Foam-like Carbon Nitride and Fe3O4 with Improved Manipulation and Photocatalytic Performance

Micro/nanomotors have emerged as a vibrant research topic in biomedical and environmental fields due to their attractive self-propulsion as well as small-scale functionalities. However, single actuated micro/nanomotors are not adaptive in facing intricate natural and industrial environments. Herein, we propose a new dual-mode-driven micromotor based on foam-like carbon nitride (f-C₃N₄) with precipitated Fe₃O₄ nanoparticles, namely, Fe₃O₄/f-C₃N₄, powered by chemical/magnetic stimuli for rapid reduction of organic pollutants. The Fe₃O₄/f-C₃N₄ motor composed of a three-dimensional (3D) porous "foam-like" structure and precipitated Fe₃O₄ nanoparticles (ca. 50 nm) not only exhibits efficient photocatalytic performance under visible light but also shows versatile and programmable motion behavior under the control of external magnetic fields. The aggregation of the micromotor under an external rotating magnetic field further enhances the catalytic activity by the increased local catalyst concentration. Furthermore, the magnetic property endows the micromotor with easy recyclability. This study provides a novel dual-mode-driven micromotor for antibiotics removal with magnetic field and light-enhanced performance in industrial wastewater treatment at a low cost.

Well-Defined Ultrasmall V-NiP2 Nanoparticles Anchored g-C3N4 Nanosheets as Highly Efficient Visible-Light-Driven Photocatalysts for H2 Evolution

Exploring low-cost and highly active, cost-effective cocatalysts is of great significance to improve the hydrogen evolution performance of semiconductor photocatalysts. Herein, a novel ultrasmall V-doped NiP2 nanoparticle, as an efficient cocatalyst, is reported to largely upgrade the photocatalytic hydrogen evolution reaction (HER) of g-C3N4 nanosheets under visible-light irradiation. Experimental results demonstrate that V-NiP2 cocatalyst can enhance the visible-light absorption ability, facilitate the separation of photo-generated electron-hole pairs and boost the transfer ability of electrons of g-C3N4. Moreover, the V-NiP2/g-C3N4 hybrid exhibits prominent photocatalytic HER activity 17 times higher than the pristine g-C3N4 counterpart, even outperforming the 1 wt.% platinum-loaded g-C3N4. This work displays that noble-metal-free V-NiP2 cocatalyst can serve as a promising and efficient alternative to Pt for high-efficiency photocatalytic H2 evolution.

VS2 wrapped Si nanowires as core-shell heterostructure photocathode for highly efficient photoelectrochemical water reduction performance

Interfacing an electrocatalyst with photoactive semiconductor surfaces is an emerging strategy to enhance the photocathode performance for the solar water reduction reaction. Herein, a core-shell heterostructure photocathode consisting of vanadium disulfide (VS₂) as a 2D layered electrocatalyst directly deposited on silicon nanowire (Si NWs) surface is realized via single-step chemical vapor deposition towards efficient hydrogen evolution under solar irradiation. In an electrochemical study, 2D VS₂/Si NWs photocathode exhibits a saturated photocurrent density (17 mA cm^-2) with a maximal photoconversion efficiency of 10.8% at -0.53 V vs. RHE in neutral electrolyte condition (pH∼7). Under stimulated irradiation, the heterostructure photocathode produces a hydrogen gas evolution around 23 μmol cm^-2 h^-1 (at 0 V vs. RHE). Further, electrochemical impedance spectroscopy (EIS) analysis reveals that the high performance of the core-shell photocathode is associated with the generation of the high density of electron-hole pairs and the separation of photocarriers with an extended lifetime. Density functional theory calculations substantiate that core-shell photocathodes are active at very low Gibbs free energy (ΔG_H*) with abundant hydrogen evolution reaction (HER) active sulphur sites. The charge density difference plot with Bader analysis of heterostructure reveals the accumulation of electrons on the sulphur sites via modulating the electronic band structure near the interface. Thus, facilitates the barrier-free charge transport owing to the synergistic effect of Si NWs@2D-VS₂ core-shell hybrid photocatalyst for enhanced solar water reduction performance.

Ferroelectricity and Schottky Heterojunction Engineering in AgNbO3: A Simultaneous Way of Boosting Piezo-photocatalytic Activity

As an efficient and economical way of dealing with organic pollutants, piezo-photocatalysis has attracted great interest. In this work, we demonstrated that ferroelectricity and Schottky heterojunction engineering could significantly enhance the piezo-photocatalytic activity of AgNbO₃. The poled 20 mol % K⁺ doped AgNbO₃ disclosed its superior piezo-photocatalytic activity of 0.131 min^-1 for 10 mg·L^-1 RhB, which is 7.8 times of the pristine one under the condition of illumination only. The designed piezo-photocatalyst also exhibited good piezo-photocatalytic stability after four cycles. These merits are attributed to the built-in electric field associated with the large spontaneous polarization and low coercive field originated from the stable ferroelectric state after ferroelectricity engineering, plus with the electron trapper effect of the in situ precipitated metal Ag particles. Our work not only provides a promising piezo-photocatalyst for degrading organic contaminants but also paves a good way for developing high piezo-photocatalytic activity catalysts.

Composition-dependent activity of ZnxCd1-xSe solid solution coupled with Ni2P nanosheets for visible-light-driven photocatalytic H2 generation

Metal selenide semiconductors have been rarely used for photocatalytic water splitting because of their poor stability and severe photocorrosion properties. Hence, designing stable metal selenides with suitable bandgap energies has considerable practical significance in photocatalytic H₂ evolution. In this work, a novel series of Zn_xCd_1-xSe (x = 0 ∼ 1) with tunable band structure were fabricated through a simple solvothermal method. Impressively, the ZnSe exhibited a maximum H₂ production rate of 1056 µmol g^-1h^-1, which was higher than that of CdSe and Zn_xCd_1-xSe solid solutions. Such visible-light photoactivity for water reduction to H₂ was attained even after 6 cycling photocatalytic experiments. Moreover, the two-dimensional (2D) Ni₂P nanosheets act as a high-efficiency cocatalyst integrated with Zn_xCd_1-xSe semiconductor to boost photocatalytic H₂ generation performance. The optimal 8% Ni₂P/ZnSe composites displayed excellent cycling stability and superior photocatalytic H₂ evolution performance (4336 µmol g^-1h^-1), which was about 4.1 times that of pure ZnSe under visible light irradiation. Photoelectrochemical (PEC), photoluminescence (PL), and time-resolved photoluminescence (TRPL) measurements reveal that the improved photoactivity Ni₂P/ZnSe photocatalysts were ascribed to the effective separation and migration of photoinduced carriers. The present work paves a pathway to explore the fabrication of Zn_xCd_1-xSe solid solutions and the hybridization of 2D transition metal phosphides nanosheets toward photocatalytic applications.

Precisely Tailoring Nitrogen Defects in Carbon Nitride for Efficient Photocatalytic Overall Water Splitting

Precisely tailoring the nitrogen defects has been verified to be a promising approach for promoting the photocatalytic efficiency of C₃N₄. Herein, two-coordinated-N vacancies are selectively introduced into the C₃N₄ framework by a facile Cl^- modification method, whereas its concentration can be facilely tuned by varying Cl^- usage in the process of thermal polymerization. Impressively, the optimal defective C₃N₄ (20 mg) exhibited superior hydrogen and oxygen evolution rates of 48.2 and 21.8 μmol h^-1, respectively, in photocatalytic overall water splitting and an apparent quantum efficiency of 6.9% at 420 nm, the highest of reported single-component C₃N₄ photocatalysts for overall water splitting. Systematic studies including XPS, DFT simulations, and NEXAFS reveal that Cl^- modification preferentially facilitates the introduction of two-coordinated-N vacancies through tuning the formation energy and promotes charge carrier separation efficiency, thereby greatly enhancing the photocatalytic efficiency. This work allows for a viable approach to rationally designing defective C₃N₄ for efficient photocatalysis.

Development and Functionalization of Visible-Light-Driven Water-Splitting Photocatalysts

With global warming and the depletion of fossil resources, our fossil fuel-dependent society is expected to shift to one that instead uses hydrogen (H₂) as a clean and renewable energy. To realize this, the photocatalytic water-splitting reaction, which produces H₂ from water and solar energy through photocatalysis, has attracted much attention. However, for practical use, the functionality of water-splitting photocatalysts must be further improved to efficiently absorb visible (Vis) light, which accounts for the majority of sunlight. Considering the mechanism of water-splitting photocatalysis, researchers in the various fields must be employed in this type of study to achieve this. However, for researchers in fields other than catalytic chemistry, ceramic (semiconductor) materials chemistry, and electrochemistry to participate in this field, new reviews that summarize previous reports on water-splitting photocatalysis seem to be needed. Therefore, in this review, we summarize recent studies on the development and functionalization of Vis-light-driven water-splitting photocatalysts. Through this summary, we aim to share current technology and future challenges with readers in the various fields and help expedite the practical application of Vis-light-driven water-splitting photocatalysts.

Synergistic poly(lactic acid) photoreforming and H2 generation over ternary NixCo1-xP/reduced graphene oxide/g-C3N4 composite

Effective utilization of photoexcited electrons and holes is always a challenge in photocatalytic reactions. Herein, we reported ternary Ni_xCo_1-xP/reduced graphene oxide/g-C₃N₄ (Ni_xCo_1-xP/rGO/CN) composite as a photocatalyst for synergistic poly(lactic acid) photoreforming and H₂ generation in alkaline aqueous solution. The rate of H₂ production over the optimal 15Ni_0·1Co_0·9P/rGO/CN reached 576.7 μmol h^-1 g^-1, which is 3.6 times as high as binary 15Ni_0·1Co_0·9P/CN composite. The apparent quantum efficiency of the optimal 15Ni_0·1Co_0·9P/rGO/CN was 1.7% at λ = 420 nm monochromatic light. Mott-Schottky analysis suggested that the photogenerated electrons transfer along the pathway of CN→rGO→Ni_0·1Co_0·9P, where rGO and Ni_0·1Co_0·9P functioned as the medium for electron transporting and reaction site for H₂ generation, respectively. Meanwhile, poly(lactic acid) was photoreformed into formate and acetate by the photogenerated holes and hydroxyl radical. This work demonstrates that ternary Ni_xCo_1-xP/rGO/CN composite can be applied as a cheap and promising photocatalyst for synergistic plastic photoreforming and H₂ generation.

Conductive polymer mediated earth abundant Z-scheme g-C3N4/Fe2O3 heterostructure with excellent photocatalytic activity

Being the second most abundant metal in the surface of the earth (5.1%), the size confined iron-based photocatalyst is of especially importance for solar energy conversion. Herein, the ternary Z-scheme...

Carbon nitride based Schottky junction with a Ni–Mo synergistic interaction for highly efficient photocatalytic hydrogen production

A CN/3NiMoP2 Schottky junction with a Ni–Mo synergistic interaction demonstrates a comparable photocatalytic HER performance to CN/3 wt% Pt and satisfactory stability.

Construction of a multidimensional CdS@MoS2 heterojunction for enhancing the activity and transfer efficiency of photogenerated carriers

A CdS@MoS2 composite photocatalyst exhibits excellent photocatalytic activity to replace noble metals by constructing a n–n heterojunction.

Copper phosphide decorated g-C3N4 catalysts for highly efficient photocatalytic H2 evolution

Designing functional heterojunctions to enhance photocatalytic hydrogen evolution is still a key challenge in the field of efficient solar energy utilization. Copper phosphides become an ideal material to serve as the cocatalysts during photocatalytic hydrogen evolution by virtue of the lower prices. In this study, we synthesized graphitic carbon nitride (g-C₃N₄) based catalysts loaded with copper phosphide (Cu₃P, Cu₉₇P₃), which exhibit superior performance in photocatalytic H₂ evolution. Ultraviolet (UV)-visible spectroscopy illustrated that the absorption of light strengthened after the loading of copper phosphide, and the time-resolved transient photoluminescence (PL) spectra showed that the separation and transfer of the photoexcited carriers greatly improved. Moreover, both copper phosphide/g-C₃N₄ photocatalysts exhibited a relatively high H₂ evolution rate: Cu₃P/g-C₃N₄ (maximum 343 μmol h^-1 g^-1), Cu₉₇P₃/g-C₃N₄ (162.9 μmol h^-1 g^-1) while copper phosphide themself exhibit no photocatalytic activity. Thus, the copper phosphides (Cu₃P, Cu₉₇P₃) work as a cocatalyst during photocatalytic H₂ evolution. The cycling experiments illustrated that both copper phosphide/g-C₃N₄ photocatalysts perform excellent stability in the photocatalytic H₂ evolution. It is worth noting that while the NaH₂PO₂ was heated in the tube furnace for phosphorization to obtain Cu₃P, the excessive PH₃ could pass through the solution of CuSO₄ to obtain Cu₉₇P₃ at the same time, which significantly improved the utilization of PH₃ and reduced the risk of toxicity. This work could provide new strategies to design photocatalysts decorated with copper phosphide for highly efficient visible-light-driven hydrogen evolution.

Emerging Cocatalysts on g-C3 N4 for Photocatalytic Hydrogen Evolution

Over the past few decades, graphitic carbon nitride (g-C₃ N₄ ) has arisen much attention as a promising candidate for photocatalytic hydrogen evolution reaction (HER) owing to its low cost and visible light response ability. However, the unsatisfied HER performance originated from the strong charge recombination of g-C₃ N₄ severely inhibits the further large-scale application of g-C₃ N₄ . In this case, the utilization of cocatalysts is a novel frontline in the g-C₃ N₄ -based photocatalytic systems due to the positive effects of cocatalysts on supressing charge carrier recombination, reducing the HER overpotential, and improving photocatalytic activity. This review summarizes some recent advances about the high-performance cocatalysts based on g-C₃ N₄ toward HER. Specifically, the functions, design principle, classification, modification strategies of cocatalysts, as well as their intrinsic mechanism for the enhanced photocatalytic HER activity are discussed here. Finally, the pivotal challenges and future developments of cocatalysts in the field of HER are further proposed.

Molecular-functionalized engineering of porous carbon nitride nanosheets for wide-spectrum responsive solar fuel generation

Carbon nitride (C₃N₄) is a promising metal-free photocatalyst for solar-to-energy conversion, but bulk carbon nitride (BCN) shows insufficient light absorption, sluggish photocarrier transfer and moderate activity for photocatalysis. Herein, a facile strategy to significantly increase solar spectrum absorption of the functionalized porous carbon nitride nanosheets (MFPCN) via molecule self-assembly engineering coupled thermal polymerization is reported. This strategy can greatly enhance the wide-solar-spectrum absorption of MFPCN up to 1000 nm than most reported carbon nitride-based photocatalysts. Experimental characterizations and theoretical calculations together display that this strategy could introduce hydroxyl groups into the structure of MFPCN as well as the rich pores and active sites at the edges of framework, which can narrow the bandgap and accelerate the transfer and separation of photoinduced carries. As a result, the optimal MFPCN photocatalyst exhibit the excellent photocatalytic hydrogen evolution rate of 7.745 mmol g^-1h^-1 under simulated solar irradiation, which is ≈13 times that of BCN with remarkable durable CO₂ reduction activities. New findings in this work will provide an approach to extend solar spectrum absorption of metal-free catalysts for solar fuel cascades.

Flower-Like Dual-Defective Z-Scheme Heterojunction g-C3N4/ZnIn2S4 High-Efficiency Photocatalytic Hydrogen Evolution and Degradation of Mixed Pollutants

Graphitic carbon nitride (g-C₃N₄) with a porous nano-structure, nitrogen vacancies, and oxygen-doping was prepared by the calcination method. Then, it was combined with ZnIn₂S₄ nanosheets containing zinc vacancies to construct a three-dimensional (3D) flower-like Z-scheme heterojunction (pCN-N/ZIS-Z), which was used for photocatalytic hydrogen evolution and the degradation of mixed pollutants. The constructed Z-scheme heterojunction improved the efficiency of photogenerated charges separation and migration, and the large surface area and porous characteristics provided more active sites. Doping and defect engineering can change the bandgap structure to improve the utilization of visible light, and can also capture photogenerated electrons to inhibit recombination, so as to promote the use of photogenerated electron-hole pairs in the photocatalytic redox process. Heterojunction and defect engineering synergized to form a continuous and efficient conductive operation framework, which achieves the hydrogen production of pCN-N/ZIS-Z (9189.8 µmol·h^-1·g^-1) at 58.9 times that of g-C₃N₄ (155.9 µmol·h^-1·g^-1), and the degradation rates of methyl orange and metronidazole in the mixed solution were 98.7% and 92.5%, respectively. Our research provides potential ideas for constructing a green and environmentally friendly Z-scheme heterojunction catalyst based on defect engineering to address the energy crisis and environmental restoration.

Plasmon-Mediated 2D/2D Phase Junction for Improved Photocatalytic Hydrogen Generation Activity

A phase junction fabricated by two crystalline phases of the same semiconductor is a promising photocatalyst with efficient charge transfer and separation. However, the weak light absorption and uncontrolled phase junction interface limit the generation and separation of photogenerated carriers. Herein, a two-dimensional (2D)/2D phase junction was prepared by growing orthorhombic WO₃ ultrathin nanosheets on hexagonal WO₃ nanosheets through a one-step hydrothermal method. The orthorhombic/hexagonal WO₃ possesses large-area phase junction interfaces, rich reactive sites, and built-in electric field, which greatly accelerate the photogenerated charge separation and transfer. Thus, the orthorhombic/hexagonal WO₃ displayed excellent photocatalytic hydrogen generation activity from water splitting under light irradiation (λ > 420 nm), which is 2.16 and 2.85 times those of orthorhombic and hexagonal WO₃ phase components. Furthermore, Au nanoparticles (about 4.5 nm in diameter) were deposited on both orthorhombic and hexagonal WO₃ nanosheets to form a plasmon-mediated phase junction. The hybrids exhibit prominent visible-light absorption and efficient charge transfer, leading to a further improved photocatalytic hydrogen generation activity. Further characterization studies demonstrate that superior photoactivity arises from the excellent visible-light-harvesting ability, appropriate band structure, and high-efficiency and multichannel transferring processes of photogenerated carriers.

Electrochemical immunosensor development based on core-shell high-crystalline graphitic carbon nitride@carbon dots and Cd0.5Zn0.5S/d-Ti3C2Tx MXene composite for heart-type fatty acid-binding protein detection

Acute myocardial infarction (AMI) is a significant health problem owing to its high mortality rate. Heart-type fatty acid-binding protein (h-FABP) is an important biomarker in the diagnosis of AMI. In this work, an electrochemical h-FABP immunosensor was developed based on Cd_0.5Zn_0.5S/d-Ti₃C₂T_x MXene (MXene: Transition metal carbide or nitride) composite as signal amplificator and core-shell high-crystalline graphitic carbon nitride@carbon dots (hc-g-C₃N₄@CDs) as electrochemical sensor platform. Firstly, a facile calcination technique was applied to the preparation of hc-g-C₃N₄@CDs and immobilization of primary antibody was performed on hc-g-C₃N₄@CDs surface. Then, the conjugation of the second antibody to Cd_0.5Zn_0.5S/d-Ti₃C₂T_x MXene was carried out by strong π-π and electrostatic interactions. The prepared electrochemical h-FABP immunosensor was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) method, Fourier-transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The prepared electrochemical h-FABP immunosensor indicated a good sensitivity with detection limit (LOD) of 3.30 fg mL^-1 in the potential range +0.1 to +0.5 V. Lastly, low-cost, satisfactory stable, and environmentally friendly immunosensor was presented for the diagnosis of acute myocardial infarction.

NiO Nanosheets Coupled With CdS Nanorods as 2D/1D Heterojunction for Improved Photocatalytic Hydrogen Evolution

Designing low-cost, environment friendly, and highly active photocatalysts for water splitting is a promising path toward relieving energy issues. Herein, one-dimensional (1D) cadmium sulfide (CdS) nanorods are uniformly anchored onto two-dimensional (2D) NiO nanosheets to achieve enhanced photocatalytic hydrogen evolution. The optimized 2D/1D NiO/CdS photocatalyst exhibits a remarkable boosted hydrogen generation rate of 1,300 μmol h-1 g-1 under visible light, which is more than eight times higher than that of CdS nanorods. Moreover, the resultant 5% NiO/CdS composite displays excellent stability over four cycles for photocatalytic hydrogen production. The significantly enhanced photocatalytic activity of the 2D/1D NiO/CdS heterojunction can be attributed to the efficient separation of photogenerated charge carriers driven from the formation of p-n NiO/CdS heterojunction. This study paves a new way to develop 2D p-type NiO nanosheets-decorated n-type semiconductor photocatalysts for photocatalytic applications.

Novel broad-spectrum-driven g-C3N4 with oxygen-linked band and porous defect for photodegradation of bisphenol A, 2-mercaptophenthiazole and ciprofloxacin

Abundant active oxygen free radicals could efficiently remove refractory organic pollutants. In previous research, the original carbon nitride can form more hydrogen peroxide, however, owing to the limitation of its band structure, the original carbon nitride cannot decompose the hydrogen peroxide to generate more active oxygen free radicals. Herein, this work reports a simple bottom-up synthesis method, which synthesize a broad-spectrum-response carbon nitride (CN-CA) with oxygen-linked band and porous defect structure, while adjusting the band structure, and the introduction of the oxygen-linked band structure can also decompose the hydrogen peroxide produced by the original carbon nitride to form more active oxygen free radicals. Instrumental characterization and analysis of experimental results revealed the important role of oxygen-linked band and porous defects in adjusting the CN-CA energy band structure and improving its visible light absorption. The optimal CN-CA displays an outstanding photocatalytic degradation ability, that degradation rate of bisphenol A (BPA) reaches 99.8% within 150 min, the reaction rate constant of which is 6.77 times higher than that of pure g-C₃N₄, as also demonstrated with 2-mercaptophenthiazole (MBT) and ciprofloxacin (CIP). Meanwhile, the excellent degradation performance under blue LED (450-462 nm) and green LED (510-520 nm) exhibits the broad-spectrum characteristics of CN-CA. The degradation pathways of BPA and MBT were analyzed via HPLC-MS. Moreover, the primary active species were detected as O₂^-, OH and h⁺ based on the trapping experiments and ESR. This research provides a new strategy for g-C₃N₄ modified by porous defects and oxygen-linked band structure for environmental remediation.

Influence of the Physical Properties on the Antibacterial and Photocatalytic Behavior of Ag-Doped Indium Sulfide Film Deposited by Spray Pyrolysis

Spray pyrolysis was used to deposit indium sulfide (In2S3) films, with or without silver doping. The films are polycrystalline, and the inclusion of Ag in the In2S3 structure leads to the formation of a solid solution, with the crystallite size of the order of tens of nanometers. In2S3 films exhibit a semiconductive behavior, and the incorporation of Ag leads to an increase of the charge carrier concentration, enhancing the electrical conductivity of the films. The small polaron hopping mechanism, deduced by the fittings according to the double Jonscher variation, explains the evolution of the direct current (dc) conductivity at high temperature of the Ag-doped indium sulfide. From impedance spectroscopy, it was found that the doped film presents dielectric relaxation, and Nyquist diagrams indicate the importance of the grain and the grain boundaries’ contributions to the transport phenomena. The physical characteristics of the films have an influence on the photocatalytic performance, achieving photodegradation efficiency above 80% (85.5% in the case of Ag doping), and on the antibacterial activity. The obtained results indicate that indium sulfide films are good candidates for environmental and biological applications, confirming a multifunctional nature.

P-Type Cobalt Phosphide Composites (CoP-Co2P) Decorated on Titanium Oxide for Enhanced Noble-Metal-Free Photocatalytic H2 Evolution Activity

Nowadays, transition-metal phosphides have been reported to function well in photocatalytic water splitting and possess great potential to substitute traditional noble-metal cocatalysts in the future. Herein, p-type cobalt phosphide (CoP-Co₂P) nanomaterials were synthesized by phosphating the solvothermally prepared Co(OH)₂ nanoflowers at a low temperature (300 °C). Then, we combined the phosphides with commercial TiO₂ through facile mechanical mixing to fabricate a useful noble-metal-free photocatalyst. The phosphating time that had an influence on the composition of phosphides was tuned, and 3 h was an ideal condition after comparison. The cobalt phosphide-modified TiO₂ at the optimal weight percentage (nominal 0.5%) exhibited the highest photocatalytic hydrogen rate of approximately 824.5 μmol g^-1 h^-1 under simulated sunlight irradiation, which was nearly equal to 160 times that of bare TiO₂ and 1.7 times that of single CoP-modified TiO₂. The CoP_x/TiO₂ heterojunction interfaces were studied using photoluminescence (PL), time-resolved PL, and photoelectrochemical methods, which revealed that the effective charge separation and transfer accelerated by the built-in electric field of p-n junction contributed significantly to the photocatalytic performance.

Bimetallic zeolite-imidazole framework-based heterostructure with enhanced photocatalytic hydrogen production activity

Bimetallic zeolite-imidazole frameworks with controllable flat band position, band gap and hydrogen evolution reaction characteristics were adopted as a photocatalytic hydrogen production catalyst. Furthermore, the g-C3N4-MoS2 2D-2D surface heterostructure was introduced to the ZnM-ZIF to facilitate the separation as well as utilization efficiency of the photo-exited charge carriers in the ZnM-ZIFs. On the other hand, the ZnM-ZIFs not only inhibited the aggregation of the g-C3N4-MoS2 heterostructure, but also improved the separation and transport efficiency of charge carriers in g-C3N4-MoS2. Consequently, the optimal g-C3N4-MoS2-ZnNi-ZIF exhibited an extraordinary photocatalytic hydrogen evolution activity 214.4, 37.5, and 3.7 times larger than that of the pristine g-C3N4, g-C3N4-ZnNi-ZIF and g-C3N4-MoS2, respectively, and exhibited a H2-evolution performance of 77.8 μmol h-1 g-1 under UV-Vis light irradiation coupled with oxidation of H2O into H2O2. This work will furnish a new MOF candidate for photocatalysis and provide insight into better utilization of porous MOF-based heterostructures for hydrogen production from pure water.

Zinc sulfide quantum dots/zinc oxide nanospheres/bismuth-enriched bismuth oxyiodides as Z-scheme/type-II tandem heterojunctions for an efficient charge separation and boost solar-driven photocatalytic performance

A novel zinc sulfide quantum dot (ZnS QD)/zinc oxide (ZnO) nanosphere/bismuth-enriched bismuth oxyiodide (Bi₄O₅I₂) tandem heterojunction photocatalyst is fabricated through two-step solvothermal, calcination and one-step hydrothermal strategies. The successfully constructed core-shell nanostructure can increase the interface area and the active sites of the composite photocatalysts. The formation of a Z-scheme/Type-II tandem heterojunction favors the transfer and spatial separation of charge carriers, in which Bi₄O₅I₂ plays a bridging role to connect ZnO and ZnS. Simultaneously, the participation of Bi₄O₅I₂ significantly shortens the band gap of the composite photocatalyst. This dual functional ZnO@Bi₄O₅I₂/ZnS composite photocatalyst has a high photocatalytic hydrogen evolution rate of 578.4 µmol g^-1h^-1 and an excellent photocatalytic degradation efficiency for bisphenol A (BPA) and 2,4,5-trichlorophenol (TCP). In addition, cycling tests show that ZnO@Bi₄O₅I₂/ZnS has a high stability, which is favorable for practical applications. This novel ZnO@Bi₄O₅I₂/ZnS Z-scheme/Type-II tandem heterojunction photocatalyst will provide new ideas for the multichannel charge transfer of other highly efficient heterojunction photocatalysts.

2D PtS nanorectangles/g-C3N4 nanosheets with a metal sulfide-support interaction effect for high-efficiency photocatalytic H2 evolution

Cocatalyst design is a key approach to acquire high solar-energy conversion efficiency for photocatalytic hydrogen evolution. Here a new in situ vapor-phase (ISVP) growth method is developed to construct the cocatalyst of 2D PtS nanorectangles (a length of ∼7 nm, a width of ∼5 nm) on the surface of g-C₃N₄ nanosheets. The 2D PtS nanorectangles/g-C₃N₄ nanosheets (PtS/CN) show an unusual metal sulfide-support interaction (MSSI), which is evidenced by atomic resolution HAADF-STEM, synchrotron-based GIXRD, XPS and DFT calculations. The effect of MSSI contributes to the optimization of geometrical structure and energy-band structure, acceleration of charge transfer, and reduction of hydrogen adsorption free energy of PtS/CN, thus yielding excellent stability and an ultrahigh photocatalytic H₂ evolution rate of 1072.6 μmol h^-1 (an apparent quantum efficiency of 45.7% at 420 nm), up to 13.3 and 1532.3 times by contrast with that of Pt nanoparticles/g-C₃N₄ nanosheets and g-C₃N₄ nanosheets, respectively. This work will provide a new platform for designing high-efficiency photocatalysts for sunlight-driven hydrogen generation.

Recent Progress of Transition Metal Phosphides for Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen evolution can effectively alleviate the troublesome global energy crisis by converting solar energy into the chemical energy of hydrogen. In order to realize efficient hydrogen generation, a variety of semiconductor materials have been extensively investigated, including TiO₂ , CdS, g-C₃ N₄ , metal-organic frameworks (MOFs), and others. In recent years, to achieve higher photocatalytic performance and reach the level of large-scale industrial applications, photocatalysts decorated with transition metal phosphides (TMPs) have shone brightly because of their low cost, stable physical and chemical properties, and substitution for precious metals of TMPs. This Review highlights the preparation methods and properties associated with photocatalysis of TMPs. Moreover, the H₂ generation efficiency of photocatalysts loaded with TMPs and the roles of TMPs in catalytic systems are also studied systematically. Apart from being co-catalysts, several TMPs can also serve as host catalysts to boost the activity of photocatalytic composites. Finally, the development prospects and challenges of TMPs are put forward, which is valuable for future researchers to expand the application of TMPs in photocatalytic directions and to develop more active photocatalytic systems.

Band Engineering and Morphology Control of Oxygen-Incorporated Graphitic Carbon Nitride Porous Nanosheets for Highly Efficient Photocatalytic Hydrogen Evolution

Graphitic carbon nitride (g-C₃N₄)-based photocatalysts have shown great potential in the splitting of water. However, the intrinsic drawbacks of g-C₃N₄, such as low surface area, poor diffusion, and charge separation efficiency, remain as the bottleneck to achieve highly efficient hydrogen evolution. Here, a hollow oxygen-incorporated g-C₃N₄ nanosheet (OCN) with an improved surface area of 148.5 m² g^-1 is fabricated by the multiple thermal treatments under the N₂/O₂ atmosphere, wherein the C-O bonds are formed through two ways of physical adsorption and doping. The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects, leading to the formation of hollow morphology, while the O-doping results in reduced band gap of g-C₃N₄. The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6 μmol g^-1 h^-1 for ~ 20 h, which is over four times higher than that of g-C₃N₄ (850.1 μmol g^-1 h^-1) and outperforms most of the reported g-C₃N₄ catalysts.

Nanostructured metal phosphides: from controllable synthesis to sustainable catalysis

Metal phosphides (MPs) with unique and desirable physicochemical properties provide promising potential in practical applications, such as the catalysis, gas/humidity sensor, environmental remediation, and energy storage fields, especially for transition metal phosphides (TMPs) and MPs consisting of group IIIA and IVA metal elements. Most studies, however, on the synthesis of MP nanomaterials still face intractable challenges, encompassing the need for a more thorough understanding of the growth mechanism, strategies for large-scale synthesis of targeted high-quality MPs, and practical achievement of functional applications. This review aims at providing a comprehensive update on the controllable synthetic strategies for MPs from various metal sources. Additionally, different passivation strategies for engineering the structural and electronic properties of MP nanostructures are scrutinized. Then, we showcase the implementable applications of MP-based materials in emerging sustainable catalytic fields including electrocatalysis, photocatalysis, mild thermocatalysis, and related hybrid systems. Finally, we offer a rational perspective on future opportunities and remaining challenges for the development of MPs in the materials science and sustainable catalysis fields.