Enhanced Schottky effect of a 2D-2D CoP/g-C3N4 interface for boosting photocatalytic H2 evolution

Constructing CoPC/g-C3N4 nanocomposites with PC bond bridged interface and van der Waals heterojunctions for enhanced photocatalytic H2 evolution

Enhancing the charge transmission rate at the interface of transition metal phosphide cocatalysts is an efficient technique to reinforce the photocatalytic activity action of semiconductors, but achieving a faster interface charge transfer rate remains a challenge. This paper reported the coupling of a two-dimensional carbon layer supported CoP (CoPC) as a non-noble metal heterostructure catalyst and a two-dimensional porous graphite carbon nitride (CN) photocatalyst to enhance the transmission rate of photogenerated carriers at the interface. Detailed characterizations and mechanism research have confirmed that the PC bond and Van der Waals heterojunction at the interface function as a novel charge transmission channel, which facilitates the effective transfer of photogenerated carriers from CN to CoP. Furthermore, the large contact area exhibited by the 2D/2D Van der Waals heterojunction offers an increased number of active sites for hydrogen evolution reactions. Consequently, the composite material (CoPC/CN) formed by the coupling of CoPC and CN has an enhanced H2 production rate of 1503 μmol∙g-1∙h-1 (AQY: 3.03 % at 400 nm) and favorable H2 production stability under visible light irradiation. This investigation not only provides a new idea for the regulation of interface charge transfer pathway but also offers new inspiration for the photocatalytic system's design with the synergistic impacts of 2D/2D VDW heterojunction and chemical bonds.

Nanostructured Li2S Cathodes for Silicon-Sulfur Batteries

Lithium-sulfur batteries are regarded as an advantageous option for meeting the growing demand for high-energy-density storage, but their commercialization relies on solving the current limitations of both sulfur cathodes and lithium metal anodes. In this scenario, the implementation of lithium sulfide (Li2S) cathodes compatible with alternative anode materials such as silicon has the potential to alleviate the safety concerns associated with lithium metal. In this direction, here, we report a sulfur cathode based on Li2S nanocrystals grown on a catalytic host consisting of CoFeP nanoparticles supported on tubular carbon nitride. Nanosized Li2S is incorporated into the host by a scalable liquid infiltration-evaporation method. Theoretical calculations and experimental results demonstrate that the CoFeP-CN composite can boost the polysulfide adsorption/conversion reaction kinetics and strongly reduce the initial overpotential activation barrier by stretching the Li-S bonds of Li2S. Besides, the ultrasmall size of the Li2S particles in the Li2S-CoFeP-CN composite cathode facilitates the initial activation. Overall, the Li2S-CoFeP-CN electrodes exhibit a low activation barrier of 2.56 V, a high initial capacity of 991 mA h gLi2S-1, and outstanding cyclability with a small fading rate of 0.029% per cycle over 800 cycles. Moreover, Si/Li2S full cells are assembled using the nanostructured Li2S-CoFeP-CN cathode and a prelithiated anode based on graphite-supported silicon nanowires. These Si/Li2S cells demonstrate high initial discharge capacities above 900 mA h gLi2S-1 and good cyclability with a capacity fading rate of 0.28% per cycle over 150 cycles.

Heterostructures Regulating Lithium Polysulfides for Advanced Lithium-Sulfur Batteries

Sluggish reaction kinetics and severe shuttling effect of lithium polysulfides seriously hinder the development of lithium-sulfur batteries. Heterostructures, due to unique properties, have congenital advantages that are difficult to be achieved by single-component materials in regulating lithium polysulfides by efficient catalysis and strong adsorption to solve the problems of poor reaction kinetics and serious shuttling effect of lithium-sulfur batteries. In this review, the principles of heterostructures expediting lithium polysulfides conversion and anchoring lithium polysulfides are detailedly analyzed, and the application of heterostructures as sulfur host, interlayer, and separator modifier to improve the performance of lithium-sulfur batteries is systematically reviewed. Finally, the problems that need to be solved in the future study and application of heterostructures in lithium-sulfur batteries are prospected. This review will provide a valuable reference for the development of heterostructures in advanced lithium-sulfur batteries.

2D-2D Nanoheterostructure of an Exposed {001}-Facet CuO and MoS2 Based Bifunctional Catalyst Showing Excellent Surface Chemistry and Conductivity for Cathodic CO2 Reduction

A novel CuO-MoS2 based heterostructure catalyst model system is proposed where a CuO nanosheet with exposed {001} facet with proper termination is the active surface for the catalysis and a MoS2 nanosheet is the supporting layer. Density functional theory (DFT) calculations were performed to validate the model. The MoS2 bilayer forms a stable heterostructure with {001} faceted CuO with different terminations exposing oxygen and copper atoms (active sites) on the surface. The heterostructure active sites with a low oxidation state of the copper atoms and subsurface oxygen atoms provide a suitable chemical environment for the selective production of multicarbon products from CO2 electrocatalytic reduction. Furthermore, our heterostructure model exhibits good electrical conductivity, efficient electron transport to active surface sites, and less interfacial resistance compared to similar heterostructure systems. Additionally, we propose a photoenhanced electrocatalysis mechanism due to the photoactive nature of MoS2. We suggest that the photogenerated carrier separation occurs because of the interface-induced dipole. Moreover, we utilized a machine learning model trained on a 2D DFT materials database to predict selected properties and compared them with the DFT results. Overall, our study provides insights into the structure-property relationship of a MoS2 supported 2D CuO nanosheet based bifunctional catalyst and highlights the advantages of heterostructure formation with selective morphology and properly terminated surface in tuning the catalytic performance of nanocomposite materials.

Efficient Visible-Light Photocatalytic Hydrogen Evolution over the In2O3@Ni2P Heterojunction of an In-Based Metal-Organic Framework

Although the engineering of visible-light-driven photocatalysts with appropriate bandgap structures is beneficial for generating hydrogen (H₂), the construction of heterojunctions and energy band matching are extremely challenging. In this study, In₂O₃@Ni₂P (IO@NP) heterojunctions are attained by annealing MIL-68(In) and combining the resulting material with NP via a simple hydrothermal method. Visible-light photocatalysis experiments validate that the optimized IO@NP heterojunction exhibits a dramatically improved H₂ release rate of 2485.5 μmol g^-1 h^-1 of 92.4 times higher than that of IO. Optical characterization reveals that the doping of IO with an NP component promotes the rapid separation of photo-induced carriers and enables the capture of visible light. Moreover, the interfacial effects of the IO@NP heterojunction and synergistic interaction between IO and NP that arises through their close contact mean that plentiful active centers are available to reactants. Notably, eosin Y (EY) acts as a sacrificial photosensitizer and has a significant effect on the rate of H₂ generation under visible light irradiation, which is an aspect that needs further improvement. Overall, this study describes a feasible approach for synthesizing promising IO-based heterojunctions for use in practical photocatalysis.

Synergetic effect of Au nanoparticles and transition metal phosphides for enhanced hydrogen evolution from ammonia-borane

The hydrogen evolution from ammonia borane is intriguing but challenging due to its sluggish kinetics. In this regard, the gold nanoparticles amalgamation with metal phosphides is speculated to be more efficient catalysts. Here, the catalysts Au/Ni₂P and Au/CoP with the high synergetic effect of Au nanoparticles and metal phosphides were synthesized for ammonia borane hydrolysis. The activity of Au/Ni₂P increases 4.8-fold (i.e., 0.08 to 0.40 L∙h^-1) compared to pristine Ni₂P, and the activity of Au/CoP increases 1.7-fold (i.e., 0.74 to 1.27 L∙h^-1) compared to pristine CoP. This reveals that the synergetic effect of Au^δ+ and (Ni₂P) ^δ- is stronger than Au^δ+ and (CoP) ^δ- which is manifested by XPS analysis. The kinetics exposes that the activation energy of Au/Ni₂P (45.28 kJ∙mole^-1) is greater than Au/CoP (31.45 kJ∙mole^-1) and the TOF of Au/Ni₂P is less than Au/CoP. This research work presents an effective approach for producing active sites of Au^δ+ and (Ni₂P & CoP) ^δ- for ammonia borane hydrolysis to enhance the H₂ evolution rate.

High-Performance Visible-Light Photocatalysts for H2 Production: Rod-Shaped Co3O4/CoO/Co2P Heterojunction Derived from Co-MOF-74

Photocatalyst systems generally consist of catalysts and cocatalysts to realize light capture, charge carrier migration, and surface redox reactions. Developing a single photocatalyst that performs all functions while minimizing efficiency loss is extremely challenging. Herein, rod-shaped photocatalysts Co₃O₄/CoO/Co₂P are designed and prepared using Co-MOF-74 as a template, which displays an outstanding H₂ generation rate of 6.00 mmol·g^-1·h^-1 when exposed to visible light irradiation. It is 12.8 times higher than pure Co₃O₄. Under light excitation, the photoinduced electrons migrate from the catalysts of Co₃O₄ and CoO to the cocatalyst Co₂P. The trapped electrons can subsequently undergo a reduction reaction to produce H₂ on the surface. Density functional theory calculations and spectroscopic measurements reveal that enhanced performance results from the extended lifetime of photogenerated carriers and higher charge transfer efficiency. The ingenious structure and interface design presented in this study may guide the general synthesis of metal oxide/metal phosphide homometallic composites for photocatalysis.

Synthesis of hierarchical Cd-Ni-MOF micro/nanostructures and derived Cd-Ni-MOF/CdS/NiS hybrid photocatalysts for efficient photocatalytic hydrogen evolution

Hierarchical micro/nanostructures assembled from nanorods and nanosheets have become promising candidates for photocatalysis. In this work, a series of hierarchical Cd-Ni-MOF micro/nanostructures, assembled from nanosheets and nanorods, were fabricated via a two-step solvothermal process involving the partial replacement of Ni²⁺ with Cd²⁺ in the Ni-MOF-74 structure. Different morphologies were obtained by considering different volume ratios of DMF and ethanol as the solvent during synthesis. Hierarchical Cd-Ni-MOF-T/CdS/NiS hybrid micro/nanostructures were synthesized by Ni²⁺ and Cd²⁺ exchange of Cd-Ni-MOFs with S^2-. The as-prepared samples, which were composed of thin nanosheets alone, exhibited the best photocatalytic H₂ evolution rate of about 40.08 mmol g^-1 h^-1. The p-n junction between CdS and NiS was found to be beneficial for the migration of photogenerated electrons from the conduction band (CB) of NiS to the CB of CdS. The heterojunction between CdS and Cd-Ni-MOF-T further promoted the transfer of an electron from the CB of CdS to the CB of Cd-Ni-MOF-T. Thus, this study demonstrated that hierarchical Cd-Ni-MOF-T/CdS/NiS architectures have a large specific surface area, leading to significantly improved photocatalytic activity.

Recent Advances in g-C3N4-Based Materials and Their Application in Energy and Environmental Sustainability

Graphitic carbon nitride (g-C₃N₄), with facile synthesis, unique structure, high stability, and low cost, has been the hotspot in the field of photocatalysis. However, the photocatalytic performance of g-C₃N₄ is still unsatisfactory due to insufficient capture of visible light, low surface area, poor electronic conductivity, and fast recombination of photogenerated electron-hole pairs. Thus, different modification strategies have been developed to improve its performance. In this review, the properties and preparation methods of g-C₃N₄ are systematically introduced, and various modification approaches, including morphology control, elemental doping, heterojunction construction, and modification with nanomaterials, are discussed. Moreover, photocatalytic applications in energy and environmental sustainability are summarized, such as hydrogen generation, CO₂ reduction, and degradation of contaminants in recent years. Finally, concluding remarks and perspectives on the challenges, and suggestions for exploiting g-C₃N₄-based photocatalysts are presented. This review will deepen the understanding of the state of the art of g-C₃N₄, including the fabrication, modification, and application in energy and environmental sustainability.

Synergistically interactive P-Co-N bonding states in cobalt phosphide-decorated covalent organic frameworks for enhanced photocatalytic hydrogen evolution

Non-noble materials with high efficiency and stability are essential for renewable energy applications. Herein, cobalt phosphide nanoparticles-decorated covalent organic frameworks (CTF-CoP) are synthesized via an in situ self-assembly method combined with the calcination process. In such a configuration, an intimate interaction between CoP and CTF matrix is gained through the Co-N chemical bonds, which not only significantly enhance the recyclability of CoP nanoparticles but also significantly improve the charge separation efficiency. Besides, the synergistically interactive P^δ--Co^δ+-N^δ- states induced by the polarization effect of N-anchoring sites benefit for the adsorption and dissociation of water molecules in CTF-CoP. Consequently, CTF-CoP exhibits a higher photocatalytic hydrogen evolution rate (261.7 μmol g^-1 h^-1) and better durability as compared with the physically fixed CTF/CoP composite (64.8 μmol g^-1 h^-1) and even the noble metal-based CTF-Pt (191.3 μmol g^-1 h^-1). This work provides an avenue to construct highly stable non-noble photocatalyst for energy conversion and also emphasizes the potential of CTFs in constructing efficient heterojunctions.

Type-II CuFe2O4/Graphitic Carbon Nitride Heterojunctions for High-Efficiency Photocatalytic and Electrocatalytic Hydrogen Generation

Solar water splitting has emerged as an urgent imperative as hydrogen emerges as an increasingly important form of energy storage. g-C₃N₄ is an ideal candidate for photocatalytic water splitting as a result of the excellent alignment of its band edges with water redox potentials. To mitigate electron-hole recombination that has limited the performance of g-C₃N₄, we have developed a semiconductor heterostructure of g-C₃N₄ with CuFe₂O₄ nanoparticles (NPs) as a highly efficient photocatalyst. Visible-light-driven photocatalytic properties of CuFe₂O₄/g-C₃N₄ heterostructures with different CuFe₂O₄ loadings have been examined with two sacrificial agents. An up to 2.5-fold enhancement in catalytic efficiency is observed for CuFe₂O₄/g-C₃N₄ heterostructures over g-C₃N₄ nanosheets alone with the apparent quantum yield of H₂ production approaching 25%. The improved photocatalytic activity of the heterostructures suggests that introducing CuFe₂O₄ NPs provides more active sites and reduces electron-hole recombination. The g-C₃N₄/CuFe₂O₄ heterostructures furthermore show enhanced electrocatalytic HER activity as compared to the individual components as a result of which by making heterostructures g-C₃N₄ with CuFe₂O₄ increased the active catalytic surface for the electrocatalytic water splitting reaction. The enhanced faradaic efficiency of the prepared heterostructures makes it a potential candidate for efficient hydrogen generation. Nevertheless, the designed heterostructure materials exhibited significant photo- and electrocatalytic activity toward the HER, which demonstrates a method for methodically enhancing catalytic performance by creating heterostructures with the best energetic offsets.

Fabrication of TaON/CdS Heterostructures for Enhanced Photocatalytic Hydrogen Evolution under Visible Light Irradiation

Developing high-performance photocatalysts for H2 production via fabricating heterojunctions has attracted much attention. Herein, we design a simple strategy to prepare composites that consist of TaON/CdS hybrids via a hydrothermal process. The results show that the pristine CdS nanoparticles loaded with 20 wt% TaON (TC4) could maximize the photocatalytic hydrogen evolution rate to 19.29 mmol g−1 h−1 under visible light irradiation, which was 2.13 times higher than that of the pristine CdS (9.03 mmol g−1 h−1) under the same conditions. The apparent quantum yield (AQY) of the TC4 nanocomposites at 420 nm was calculated to be 18.23%. The outstanding photocatalytic performance of the composites can be ascribed to the formation of heterojunctions. The electrochemical measurements indicate that the decoration facilitates the generation of extra photo-electrons, prolonging the recombination rate of photogenerated charge carriers, offering adequate active sites and improving catalytic stability. This study sheds light on the construction strategy and the deep understanding of the novel CdS-based composites for high-performance photocatalytic H2 production.

Encapsulating N‑doped graphite carbon in MoO2 as a novel cocatalyst for boosting photocatalytic hydrogen evolution

Generally, it is important to ameliorate the co-catalyst used in photocatalytic hydrogen evolution reactions (PHERs) to achieve efficient transfer and separation of photogenerated carriers, decrease the surface reaction energy barrier, and hence improve the photocatalytic activity. In this study, N-doped graphite carbon (GC) was introduced in situ to MoO₂ to ensure the presence of well-dispersed active sites, lower the overpotential of hydrogen evolution, and further achieve high conductivity. Then, the MoO₂/GC composite obtained was used as a co-catalyst of ZnIn₂S₄ (ZIS) in a PHER, resulting in a great improvement in the photocatalytic activity. Given the metallicity and large work function of MoO₂/GC, a Schottky interface can form between MoO₂/GC and ZIS, which accelerates the transmission of photogenerated electrons. As a result, the separation efficiency of photogenerated carriers improves, whereas the surface overpotential of PHERs clearly decreases for ZIS. This study proposes a new idea for exploiting efficient co-catalysts and promotes the wide and heavy use of carbon materials in the field of solar energy conversion.

Defect-rich cobalt pyrophosphate hybrids decorated Cd0.5Zn0.5S for efficient photocatalytic hydrogen evolution: Defect and interface engineering

Photocatalysts with highly efficient charge separation are of critical significance for improving photocatalytic hydrogen production performance. Herein, a cost-effective and high-performance composite photocatalyst, cobalt-phosphonate-derived defect-rich cobalt pyrophosphate hybrids (CoPPi-M) modified Cd_0.5Zn_0.5S is rationally devised via defect and interface engineering, in which the co-catalyst CoPPi-M delivers a strong interaction with host photocatalyst Cd_0.5Zn_0.5S, rendering Cd_0.5Zn_0.5S/CoPPi-M with a remarkably improved efficiency of charge separation and migration. Besides, Cd_0.5Zn_0.5S/CoPPi-M exhibits a hydrophilic surface with ample access to electrons and a strong reduction ability of electrons. Benefiting from these advantages, the integration of defect-rich cobalt pyrophosphate and Cd_0.5Zn_0.5S enables Cd_0.5Zn_0.5S/CoPPi-M-5% with high photocatalytic H₂ production rate of 6.87 mmol g^-1h^-1, which is 2.46 times higher than that of pristine Cd_0.5Zn_0.5S, and the notable apparent quantum efficiency (AQE) is 20.7% at 420 nm. This work provides a promising route for promoting the photocatalytic performance of non-precious hybrid photocatalyst via defect and interface engineering, and advances energy-generation and environment-restoration devices.

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.

A novel type-II NiCo-LDH/CeO2 heterojunction for highly efficient photocatalytic H2 production

The study of environmentally friendly semiconductor photocatalysts has important practical significance for efficient photocatalytic hydrogen evolution.

Cu3P@CoO core-shell heterostructure with synergistic effect for highly efficient hydrogen evolution

The sluggish charge transfer and poor intrinsic activity are the obstacles that limit the development for electrocatalysts on hydrogen evolution. A novel core-shell heterostructure composed of Cu₃P nanowires with supported CoO nanosheets was synthesized. Owing to numerous active sites and synergistic effect, the as-prepared Cu₃P@CoO was highly efficient for hydrogen evolution and outperformed the single component. The theoretical calculations demonstrate that Cu₃P@CoO had a zero bandgap for the incorporation of metallic Cu₃P, which can greatly accelerate the charge transfer. Besides, the adsorption free energy of intermediates on Cu₃P@CoO can also be optimized, leading to a small energy barrier in the reaction pathway, and thereby an increased intrinsic activity. This work highlights the significance of exploiting the synergistic effect of the heterostructure on the charge transfer and intrinsic activity when designing highly efficient electrocatalysts for hydrogen evolution.

CdS Reinforced with CoSX /NiCo-LDH Core-shell Co-catalyst Demonstrate High Photocatalytic Hydrogen Evolution and Durability in Anhydrous Ethanol

At present, inefficient charge separation of single photocatalyst impedes the development of photocatalytic hydrogen evolution. In this work, the CoS_X /NiCo-LDH core-shell co-catalyst was cleverly designed, which exhibit high activity and high stability of hydrogen evolution in anhydrous ethanol system when coupled with CdS. Under visible light (λ≥420 nm) irradiation, the 3 %Co/NiCo/CdS composite photocatalyst exhibits a surprisingly high photocatalytic hydrogen evolution rate of 20.67 mmol g^-1  h^-1 , which is 59 times than that of the original CdS. Continuous light for 20 h still showed good cycle stability. In addition, the 3 %Co/NiCo/CdS composite catalyst also shows good hydrogen evolution performance under the Na₂ S/Na₂ SO₃ and lactic acid system. The fluorescence (PL), ultraviolet-visible diffuse reflectance (UV-vis) and photoelectrochemical tests show that the coupling of CdS and CoS_X /NiCo-LDH not only accelerates the effective transfer of charges, but also greatly increases the absorption range of CdS to visible light. Therefore, the hydrogen evolution activity of the composite photocatalyst has been significantly improved. This work will provide new insights for the construction of new co-catalysts and the development of composite catalysts for hydrogen evolution in multiple systems.

Recent advances in Co-based co-catalysts for efficient photocatalytic hydrogen generation

Recent progress in photocatalytic hydrogen generation reaction highlights the critical role of co-catalysts in enhancing the solar-to-fuel conversion efficiency of diverse band-matched semiconductors. Because of the compositional flexibility, adjustable microstructure, tunable crystal phase and facet, cobalt-based co-catalysts have stimulated tremendous attention as they have high potential to promote hydrogen evolution reaction. However, a comprehensive review that specifically focuses on these promising materials has not been reported so far. Therefore, this present review emphasizes the recent progress in the pursuing of highly efficient Co-based co-catalysts for water splitting, and the advances in such materials are summarized through the analysis of structure-activity relationships. The fundamental principles of photocatalytic hydrogen production are profoundly outlined, followed by an elaborate discussion on the crucial parameters influencingthe reaction kinetics. Then, the co-catalytic reactivities of various Co-based materials involving Co, Co oxides, Co hydroxides, Co sulfides, Co phosphides and Co molecular complexes, etc, are thoroughly discussed when they are coupled with host semiconductors, with an insight towards the ultimateobjective of achieving a rationally designed photocatalyst for enhancing water splitting reaction dynamics. Finally, the current challenge and future perspective of Co-based co-catalysts as the promising noble-metal alternative materials for solar hydrogen generation are proposed and discussed.

Constructing electrostatic self-assembled ultrathin porous red 2D g-C3N4/Fe2N Schottky catalyst for high-efficiency tetracycline removal in photo-Fenton-like processes

The traditional heterogeneous photo-Fenton reaction was mainly restricted by the fewer surface-active sites, low Fe³⁺/Fe²⁺ transformation and H₂O₂ activation efficiency of catalyst. This work designed and fabricated the efficient photo-Fenton Schottky catalysts via a facile electrostatic self-assembly of metallic Fe₂N nanoparticles scattering on the surface of red g-C₃N₄ (ultrathin porous oxygen-doped 2D g-C₃N₄ nanosheets). The porous morphology and exceptional electrical structure of red g-C₃N₄ endowed more active sites and facilitated the photoexcited charge separation. Benefitting from the Schottky effect and unique dimensional coupling structure, the strong visible light absorption and fast spatial charge transfer were realized in the Schottky junction system. More strikingly, Fe₂N as an efficient co-catalyst was in favor of the trap and export of e^-, leading to the Fe³⁺/Fe²⁺ transformation and H₂O₂ activation during the photo-Fenton process. Accordingly, the as-prepared catalysts revealed outstanding activity in photo-Fenton like degradation of tetracycline (TC) although under 5 W white LED light irradiation. Furthermore, the reasonable degradation pathway of TC and corresponding toxicity of the intermediates, as well as the photo-Fenton catalytic mechanism were interpreted and discussed in detail. This study would be a great aid in the development of various Schottky catalysts for heterogeneous photo-Fenton-based environmental remediation systems.

Photocatalytic overall water splitting without noble-metal: Decorating CoP on Al-doped SrTiO3

CoP, a noble-metal-free cocatalyst, was first introduced onto the surface of Al-doped SrTiO₃ (Al:STO) via an in situ photodeposition-phosphorization method for photocatalytic overall water splitting (POWS) into stoichiometric H₂ and O₂. Compared with pure Al:STO, the POWS activity was enhanced by a factor of ~ 421 over 1.0%CoP/Al:STO, with the highest evolution rates of 2106 and 1002 μmol h^-1 g^-1 for H₂ and O₂, respectively. The mechanism for the remarkably boosted POWS activity was systematically analyzed based on the comprehensive characterization. On the one hand, benefiting from the in situ photodeposition process, CoP with metallic character were intimately decorated onto the surface of Al:STO and accelerated the separation and migration of photoinduced charge carriers. On the other hand, CoP, serving as reactive sites for H₂ evolution reaction, lowered the overpotential and facilitated the surface reduction reaction, thereby enhancing the POWS activity. Furthermore, Cr₂O₃ was photodeposited on the surface of 1.0%CoP/Al:STO composite to suppress the undesired reverse reaction and the POWS activity was further enhanced up to 3558 and 1722 μmol h^-1 g^-1 for H₂ and O₂, respectively, with apparent quantum yield of 7.1% at 350 ± 10 nm. This work presents a new avenue for designing POWS system without noble-metal cocatalyst.

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.

0D ultrafine ruthenium quantum dot decorated 3D porous graphitic carbon nitride with efficient charge separation and appropriate hydrogen adsorption capacity for superior photocatalytic hydrogen evolution

Ultrafine Ru quantum dot decorated 3D porous g-C₃N₄ (U-Ru/3DpCN) photocatalysts were prepared. The optimal photocatalyst U-1Ru/3DpCN achieves an excellent H₂ evolution of 2945.47 μmol g⁻¹ h⁻¹ under visible light with a high AQE of 9.5% at 420 nm.

In situ intercalation and exploitation of Co3O4 nanoparticles grown on carbon nitride nanosheets for highly efficient degradation of methylene blue

The low surface area, poor electrical conductivity, and rapid electron-hole recombination in bulk C3N4 limit its photocatalytic activity, which makes it challenging to improve the performance of bulk C3N4. Herein, an effective strategy is proposed to fabricate Co3O4/C3N4 heterojunctions (Co3O4 nanoparticles grown on C3N4 nanosheets), where bulk C3N4 is exfoliated to thin nanosheets. The bulk C3N4 precursor was synthesized with the hydrothermal treatment of melamine solution, and Co2+ ions were then inserted into the interlayer of the precursor through a vacuum-assisted intercalation process. Subsequently, the precursor was exfoliated to C3N4 nanosheets, and 15 nm Co3O4 nanoparticles were simultaneously formed using in situ thermal polycondensation. The Brunauer-Emmett-Teller (BET) specific surface area of the prepared heterojunction was 21 times higher than that of bulk C3N4, and thus more active sites were exposed on the surface of the heterostructure. Co3O4 nanoparticles contained oxygen vacancies, and the type-II transfer mechanism between these nanoparticles and C3N4 could be used to effectively separate photogenic carriers and improve the electron mobility. As expected, the heterostructure exhibited an excellent photocatalyzed degradation rate of 99.5% for methylene blue within 30 min (10 mg catalyst, wavelength >420 nm) under visible light irradiation, which was nearly three times higher than that of bulk C3N4. Electron paramagnetic resonance (EPR) analysis indicated that ˙O2- was the main reactive oxidizing species during the degradation process.

CoP QD anchored carbon skeleton modified CdS nanorods as a co-catalyst for photocatalytic hydrogen production

An important strategy to improve the performance of catalysts is loading nanoparticle co-catalysts of better dispersion and conductivity. In this work, the ZIF-67-derived CoP quantum dot (QD) anchored graphitized carbon skeleton as a co-catalyst is loaded on CdS nanorods (NRs), while the CoP QDs derived from ZIF-67 are anchored to the carbon skeleton under phosphation and carbonization simultaneously. The porous, graphitized carbon skeleton can not only disperse CoP QDs, increasing active sites for the hydrogen reduction reaction, but also provide electron transfer channels, promoting electron transfer and increasing conductivity. In addition, the metallicity of CoP QDs makes it possible to form Schottky junctions, which is beneficial to the electron transfer at the interface. The results show that the composite photocatalyst can extensively improve the photocatalytic activity and stability, the H2 production rate is 104 947 μmol h-1 g-1 under visible light irradiation (λ ≥ 400 nm), up to 55.2 times that of bare CdS NRs, the apparent quantum yield (AQY) reaches a high value of 32.16% at 420 nm, and the structure of the photocatalyst did not change after the reaction. This work provides an innovative method for the preparation of highly efficient noble metal-free photocatalysts for the conversion of solar energy into hydrogen energy, which has bright prospects in industrial application.

Toward enhanced photocatalytic activity of graphite carbon nitride through rational design of noble metal-free dual cocatalysts

The g-C3N4-MoS2-M(OH)x ternary heterostructures were designed and fabricated for the first time. The embedding of noble-metal-free MoS2-M(OH)x dual cocatalysts over g-C3N4 nanosheets led to obvious synergistic effect for improving the transport as well as utilization efficiency of photo-generated charge carriers. Consequently, the optimal ternary heterostructure (g-C3N4-MoS2-Ni(OH)2) exhibited photocatalytic hydrogen production activity 4.5 times larger than the sum of the photocatalytic HER activity of g-C3N4-MoS2 and g-C3N4-Ni(OH)2. More significantly, even in the absence of the sacrificial agent, the g-C3N4-MoS2-Ni(OH)2 ternary heterostructure exhibited a photocatalytic HER activity of 0.3 mmol h-1 g-1 with considerable H2O2 production under UV-visible light.