The embedded CuInS2 into hollow-concave carbon nitride for photocatalytic H2O splitting into H2 with S-scheme principle

Enhancing Photocatalytic Activities for Sustainable Hydrogen Evolution on Structurally Matched CuInS2/ZnIn2S4 Heterojunctions

Effective charge separation and migration pose a critical challenge in the field of solar-driven hydrogen production. In this work, a Z-scheme structured CuInS2/ZnIn2S4 heterojunction was successfully fabricated through a two-step hydrothermal synthesis method to significantly enhance the efficiency of solar-to-hydrogen energy conversion. Structural characterization revealed that the lattice-matched CuInS2/ZnIn2S4 heterojunction exhibits an enlarged interfacial contact area, which facilitates the transfer and separation of photogenerated charges. Microscopic analysis indicated that the CuInS2/ZnIn2S4 composite material has a tightly interwoven interface and a morphology resembling small sugar cubes. Photoelectrochemical spectroscopy analysis demonstrated that the heterojunction structure effectively enhances visible light absorption and charge separation efficiency, leading to an improvement in photocatalytic activity. Hydrogen production experimental data indicated that the CuInS2/ZnIn2S4 heterojunction photocatalyst prepared with a CuInS2 content of 20 wt% exhibits the highest hydrogen evolution rate, reaching 284.9 μmol·g-1·h-1. Moreover, this photocatalyst maintains robust photocatalytic stability even after three consecutive usage cycles. This study demonstrated that the Z-scheme CuInS2/ZnIn2S4 heterojunction photocatalyst exhibits enhanced hydrogen evolution efficiency, offering an effective structural design for harnessing solar energy to obtain hydrogen fuel. Therefore, this heterojunction photocatalyst is a promising candidate for practical applications in solar hydrogen production.

Emergence of CuInS2 derived photocatalyst for environmental remediation and energy conversion

Hydrogen production, catalytic organic synthesis, carbon dioxide reduction, environmental purification, and other major fields have all adopted photocatalytic technologies due to their eco-friendliness, ease of use, and reliance on sunlight as the driving force. Photocatalyst is the key component of photocatalytic technology. Thus, it is of utmost importance to produce highly efficient, stable, visible-light-responsive photocatalysts. CIS stands out among other visible-light-response photocatalysts for its advantageous combination of easy synthesis, non-toxicity, high stability, and suitable band structure. In this study, we took a brief glance at the synthesis techniques for CIS after providing a quick introduction to the fundamental semiconductor features, including the crystal and band structures of CIS. Then, we discussed the ways doping, heterojunction creation, p-n heterojunction, type-II heterojunction, and Z-scheme may be used to modify CIS's performance. Subsequently, the applications of CIS towards pollutant degradation, CO2 reduction, water splitting, and other toxic pollutants remediation are reviewed in detail. Finally, several remaining problems with CIS-based photocatalysts are highlighted, along with future potential for constructing more superior photocatalysts.

Synthesis and hybridization of CuInS2 nanocrystals for emerging applications

Copper indium sulfide (CuInS2) is a ternary A(I)B(III)X(VI)2-type semiconductor featuring a direct bandgap with a high absorption coefficient. In attempts to explore their practical applications, nanoscale CuInS2 has been synthesized with crystal sizes down to the quantum confinement regime. The merits of CuInS2 nanocrystals (NCs) include wide emission tunability, a large Stokes shift, long decay time, and eco-friendliness, making them promising candidates in photoelectronics and photovoltaics. Over the past two decades, advances in wet-chemistry synthesis have achieved rational control over cation-anion reactivity during the preparation of colloidal CuInS2 NCs and post-synthesis cation exchange. The precise nano-synthesis coupled with a series of hybridization strategies has given birth to a library of CuInS2 NCs with highly customizable photophysical properties. This review article focuses on the recent development of CuInS2 NCs enabled by advanced synthetic and hybridization techniques. We show that the state-of-the-art CuInS2 NCs play significant roles in optoelectronic and biomedical applications.

Increasing the Photocatalytic Hydrogen Generation Activity of CdS Nanorods by Introducing Interfacial and Polarization Electric Fields

Cadmium sulfide (CdS) is a photocatalyst widely used for efficient H2 production under visible light irradiation, due to its narrow bandgap and suitable conduction band position. However, the fast recombination of carriers results in their low utilization. In order to improve photocatalytic hydrogen production, it reports the successful introduction of metallic Cd and S vacancies on CdS nanorods (CdS NRs) by a facile in situ chemical reduction method, using a thermal treatment process. This procedure generates interfacial and polarization electric fields, that significantly improve the photocatalytic hydrogen production performance of CdS NRs in sodium sulfide and sodium sulfite aqueous solutions, under visible light irradiation (λ >420 nm). The introduction of these electric fields is believed to improve charge separation and facilitate faster interfacial charge migration, resulting in a significantly optimized catalyst, with a photocatalytic hydrogen evolution rate of up to 10.6 mmol-1  g-1  h-1 with apparent quantum efficiency (AQE) of 12.1% (420 nm), which is 8.5 times higher than that of CdS. This work provides a useful method to introduce metallic and S vacancies on metal sulfide photocatalysts to build local polarization and interfacial electric fields for high-performance photocatalytic H2 production.

Enhanced photocatalytic activity of S-doped graphitic carbon nitride hollow microspheres: Synergistic effect, high-concentration antibiotic elimination and antibacterial behavior

For the past few years, graphitic carbon nitride (g-C₃N₄) has been widely used to eliminate environmental pollutants, but limited active site on surface and low separation/migration ability suppress its practical uses. Herein, we adopted a supramolecular self-assembly route followed with S doping to synthesize S-doped g-C₃N₄ with a hollow microsphere composition (SCNHM), where the shell was demonstrated to compose of ultrathin nanosheets. The unique structural characteristics endow the SCNHM with high specific surface area (∼81 m² g^-1) to provide abundant reaction sites and enhanced light-harvesting due to the light-scattering effect of hollow structure. Moreover, the S dopant meliorated the electronic structure to narrow the bandgap and promoted the charge separation/transfer capability. With this synergistic effect, the SCNHM presented greatly improved photocatalytic activity for degrading tetracycline hydrochloride (TC) compared to the CN, SCN and CNHM samples. This photocatalyst could eliminate high-concentration TC (50 mg L^-1) in 18 min, and the 30 min removal efficiencies of 100 mg L^-1 and 200 mg L^-1 reached 92 % and 60 %, which is much better than the reported photocatalysts in literatures (usually ≤ 20 mg L^-1). Additionally, the good photocatalytic durability was confirmed and the degradation pathway of TC was proposed. Furthermore, the SCNHM was proved to meanwhile possess superior performance for inactivating the typical Gram-positive bacterium of Staphylococcus aureus (S. aureus) and the typical Gram-negative bacterium of Escherichia coli (E. coli). Finally, based on determination of band alignment and detection of active species, a plausible photocatalytic mechanism was proposed.

Indium selenide/silver phosphate hollow microsphere S-scheme heterojunctions for photocatalytic hydrogen production with simultaneous degradation of tetracycline

Designing heterojunction photocatalysts with strong interfacial interactions is an effective way to reduce the recombination of photogenerated charge carriers. Here, silver phosphate (Ag₃PO₄) nanoparticles are coupled with hollow flower-like indium selenide (In₂Se₃) microspheres by a facile Ostwald ripening and in-situ growth method, resulting in the construction of In₂Se₃/Ag₃PO₄ hollow microsphere step-scheme (S-scheme) heterojunction with a large contact interface. The flower-like In₂Se₃ with hollow and porous structure provides a large specific surface area and numerous active sites for photocatalytic reactions to take place. The photocatalytic activity was tested by measuring the hydrogen evolution from antibiotic wastewater, and the H₂ evolution rate of In₂Se₃/Ag₃PO₄ reached 4206.4 µmol g^-1h^-1 under visible light, which is approximately 2.8 times greater than that of In₂Se₃. In addition, the amount of tetracycline (TC) degradation when it was used as a sacrificial agent is about 54.4% after 1 h. On the one hand, Se-P chemical bonds act as electron transfer channels in the S-scheme heterojunctions, which can facilitate the migration and separation of photogenerated charge carriers. On the other hand, the S-scheme heterojunctions can retain the useful holes and electrons with higher redox capacities, which is very favorable for the generation of more •OH radicals and the photocatalytic activity is greatly enhanced. This work provides an alternative design approach for photocatalysts toward hydrogen evolution in antibiotic wastewater.

Bi(Ⅲ) and Ce(Ⅳ) functionalized carbon nitride photocatalyst for antibiotic degradation: Synthesis, toxicity, and mechanism investigations

Graphite-phase carbon nitride (g-C₃N₄) has shown great potential for antibiotic wastewater treatment due to its unique electronic structure and corresponding to visible light. In this study, a series of Bi/Ce/g-C₃N₄ photocatalysts with different doping amount were developed by direct calcination method for Rhodamine B and sulfamethoxazole photocatalytic degradation. The experiment result shows that the photocatalytic performance of Bi/Ce/g-C₃N₄ catalysts were better than that of single component samples. Under the optimal experimental conditions, the degradation rates of RhB (20 min) and SMX (120 min) by 3Bi/Ce/g-C₃N₄ reached 98.3% and 70.5%, respectively. The theoretical calculation results of DFT show that after Bi and Ce doping modification, the band-gap width of g-C₃N₄ is reduced to 1.215 eV and carrier migration rate is greatly improved. The enhanced photocatalytic activity was mainly attributed to the capture of electrons after doping modification, which inhibition of photogenerated carriers recombination and reduced the gap width. The cyclic treatment experiment of sulfamethoxazole showed that Bi/Ce/g-C₃N₄ catalysts had good stability. Ecosar evaluation and leaching toxicity test showed that Bi/Ce/g-C₃N₄ can be safely used for wastewater treatment. This study provides a perfect strategy for modifying g-C₃N₄ and a new way to improve the photocatalytic performance.

Copper indium sulfide quantum dots in photocatalysis

Since the advent of photocatalytic technology, scientists have been searching for semiconductor materials with high efficiency in solar energy utilization and conversion to chemical energy. Recently, the development of quantum dot (QD) photocatalysts has attracted much attention because of their unique characteristics: small size, quantum effects, strong surface activity, and wide photoresponse range. Among ternary chalcogenide semiconductors, CuInS₂ QDs are increasingly examined in the field of photocatalysis due to their high absorption coefficients, good matching of the absorption range with sunlight spectrum, long lifetimes of photogenerated electron-hole pairs and environmental sustainability. In this review paper, the structural and electronic properties, synthesis methods and various photocatalytic applications of CuInS₂ QDs are systematically expounded. The current research status on the photocatalytic properties of materials based on CuInS₂ QD is discussed combined with the existing modification approaches for the enhancement of their performances. Future challenges and new development opportunities of CuInS₂ QDs in the field of photocatalysis are then prospected.

Graphitic carbon nitride-based photocatalysts in the applications of environmental catalysis

Semiconductor photocatalytic technology has shown great prospects in converting solar energy into chemical energy to mitigate energy crisis and solve environmental pollution problems. The key issue is the development of high-efficiency photocatalysts. Various strategies in the state-of-the-art advancements, such as heterostructure construction, heteroatom doping, metal/single atom loading, and defect engineering, have been presented for the graphitic carbon nitride (g-C₃N₄)-based nanocomposite catalysts to design their surface chemical environments and internal electronic structures to make them more suitable for different photocatalytic applications. In this review, nanoarchitecture design, synthesis methods, photochemical properties, potential photocatalytic applications, and related reaction mechanisms of the modified high-efficiency carbon nitride-based photocatalysts were briefly summarized. The superior photocatalytic performance was identified to be associated with the enhanced visible-light response, fast photoinduced electron-hole separation, efficient charge migration, and increased unsaturated active sites. Moreover, the further advance of the visible-light harvesting and solar-to-energy conversions are proposed.

Cooperative Coupling of H2 O2 Production and Organic Synthesis over a Floatable Polystyrene-Sphere-Supported TiO2 /Bi2 O3 S-Scheme Photocatalyst

Cooperative coupling of photocatalytic H₂ O₂ production with organic synthesis has an expansive perspective in converting solar energy into storable chemical energy. However, traditional powder photocatalysts suffer from severe agglomeration, limited light absorption, poor gas reactant accessibility, and reusable difficulty, which greatly hinders their large-scale application. Herein, floatable composite photocatalysts are synthesized by immobilizing hydrophobic TiO₂ and Bi₂ O₃ on lightweight polystyrene (PS) spheres via hydrothermal and photodeposition methods. The floatable photocatalysts are not only solar transparent, but also upgrade the contact between reactants and photocatalysts. Thus, the floatable step-scheme (S-scheme) TiO₂ /Bi₂ O₃ photocatalyst exhibits a drastically enhanced H₂ O₂ yield of 1.15 mm h^-1 and decent furfuryl alcohol conversion to furoic acid synchronously. Furthermore, the S-scheme mechanism and dynamics are systematically investigated by in situ irradiated X-ray photoelectron spectroscopy and femtosecond transient absorption spectrum analyses. In situ Fourier transform infrared spectroscopy and density functional theory calculations reveal the mechanism of furoic acid evolution. The ingenious design of floatable photocatalysts not only furnishes insight into maximizing photocatalytic reaction kinetics but also provides a new route for highly efficient heterogeneous catalysis.

Breaking the Limitation of Elevated Coulomb Interaction in Crystalline Carbon Nitride for Visible and Near-Infrared Light Photoactivity

Most near-infrared (NIR) light-responsive photocatalysts inevitably suffer from low charge separation due to the elevated Coulomb interaction between electrons and holes. Here, an n-type doping strategy of alkaline earth metal ions is proposed in crystalline K⁺ implanted polymeric carbon nitride (KCN) for visible and NIR photoactivity. The n-type doping significantly increases the electron densities and activates the n→π* electron transitions, producing NIR light absorption. In addition, the more localized valence band (VB) and the regulation of carrier effective mass and band decomposed charge density, as well as the improved conductivity by 1-2 orders of magnitude facilitate the charge transfer and separation. The proposed n-type doping strategy improves the carrier mobility and conductivity, activates the n→π* electron transitions for NIR light absorption, and breaks the limitation of poor charge separation caused by the elevated Coulomb interaction.

Emerging S-Scheme Photocatalyst

Photocatalysis is a green technology to use ubiquitous and intermittent sunlight. The emerging S-scheme heterojunction has demonstrated its superiority in photocatalysis. This article covers the state-of-the-art progress and provides new insights into its general designing criteria. It starts with the challenges confronted by single photocatalyst from the perspective of energy dissipation by borrowing the common behaviors in the dye molecule. Subsequently, other problems faced by single photocatalyst are summarized. Then a viable solution for these problems is the construction of heterojunctions. To overcome the problems and mistakes of type-II and Z-scheme heterojunctions, S-scheme heterojunction is proposed and the underlying reaction mechanism is summarized. Afterward, the design principles for S-scheme heterojunction are proposed and four types of S-scheme heterojunctions are suggested. Following this, direct characterization techniques for testifying the charge transfer in S-scheme heterojunction are presented. Finally, different photocatalytic applications of S-scheme heterojunctions are summarized. Specifically, this work endeavors to clarify the critical understanding on curved Fermi level in S-scheme heterojunction interface, which can help strengthen and advance the fundamental theories of photocatalysis. Moreover, the current challenges and prospects of the S-scheme heterojunction photocatalyst are critically discussed.

S-Scheme heterojunction based on the in situ coated core–shell NiCo2S4@WS2 photocatalyst was constructed for efficient photocatalytic hydrogen evolution

A core–shell structure was formed on the surface of NCS in situ loaded with WS, and efficient photocatalytic hydrogen evolution was achieved by constructing a reasonable S-scheme heterojunction.

Effects of various alcohol sacrificial agents on hydrogen evolution based on CoS2@SCN nanomaterials and its mechanism

Visible light induced photocatalysis converted solar energy to chemical energy in the form of hydrogen. g-C₃N₄ modified by thermal oxidation etching, doped S, and nonprecious metal cocatalyst CoS₂ (CoS₂@SCN) were used for photocatalytic hydrogen production. And then the charge transfer behavior and mechanism of various alcohol sacrificial agents on hydrogen evolution was analyzed by optical characterization, impedance analysis, Mott-Schottky, and photocurrent tests. The relationship between the structure and catalytic performance was also explored using characterization methods. The results showed that CoS₂ significantly improved the light absorption of g-C₃N₄, and carrier migration and separation. And when the sacrificial agent was triethanolamine, the nanocomposite CoS₂@SCN exhibited best catalytic performance with the highest hydrogen activity of 223.6 μmol g^-1 h^-1, the minimum volume in-phase charge transfer resistance with 55.19 Ω and the maximum photocurrent and photocurrent density with 5.5 μA cm^-2 and 0.63 mA cm^-2. The more negatively charged surface of organic alcohols were, the easier they were to react with holes, thus enhanced charge transfer and hydrogen production efficiency. This report provides guidance for the selection of hydrogen producing sacrificial agents and preparation of highly charge-efficient catalysts. And it also provides a theoretical basis for hydrogen production from wastewater and environmental remediation.

MOF-derived sulfur vacancies rich CdS nanoparticles in situ growth on 2D polymer for highly efficient photocatalytic hydrogen generation

For heterojunction photocatalytic materials, the size of nanoparticles and electron-hole separation efficiency have a great influence on the photocatalytic hydrogen production activity. In this work, for the first time, a...

Hierarchically Porous ZnO/g-C3N4 S-Scheme Heterojunction Photocatalyst for Efficient H2O2 Production

The design of photocatalysts with hierarchical pore sizes is an effective method to improve mass transport, enhance light absorption, and increase specific surface area. Moreover, the construction of a heterojunction at the interface of two semiconductor photocatalysts with suitable band positions plays a crucial role in separating and transporting charge carriers. Herein, ZIF-8 and urea are used as precursors to prepare hierarchically porous ZnO/g-C₃N₄ S-scheme heterojunction photocatalysts through a two-step calcination method. This S-scheme heterojunction photocatalyst shows high activity toward photocatalytic H₂O₂ production, which is 3.4 and 5.0 times higher than that of pure g-C₃N₄ and ZnO, respectively. The mechanism of charge transfer and separation within the S-scheme heterojunction is studied by Kelvin probe, in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS), and electron paramagnetic resonance (EPR). This research provides an idea of designing S-scheme heterojunction photocatalysts with hierarchical pores in efficient photocatalytic hydrogen peroxide production.

Cyano group-enriched crystalline graphitic carbon nitride photocatalyst: Ethyl acetate-induced improved ordered structure and efficient hydrogen-evolution activity

The molten salt-assisted route is one of the most important methods to improve the crystallinity of conventionally disordered bulk graphitic carbon nitride (g-C₃N₄). However, the residual potassium ions from potassium chloride/lithium chloride molten salt can greatly impact the ordered structure of g-C₃N₄ and serve as the recombination centers of photoinduced carriers, causing limited photocatalytic hydrogen-evolution performance. In this article, the ethyl acetate-mediated method is first developed to not only further improve the ordered structure of traditional crystalline g-C₃N₄, but also produce more cyano groups for preparing highly efficient g-C₃N₄ photocatalysts. Herein, the ethyl acetate can gradually hydrolyze to produce hydrogen ions, which can promote the more ordered sheet-like structure and more cyano groups by effective removal of residual potassium ions in the traditional crystalline g-C₃N₄, leading to the formation of cyano group-enriched crystalline g-C₃N₄ photocatalysts (CC-CN). As a result, the resultant CC-CN displays the remarkably enhanced photocatalytic hydrogen-evolution performance (295.30 µmol h^-1 with an apparent quantum efficiency about 12.61%), in comparison to the bulk g-C₃N₄ (14.97 µmol h^-1) and traditional crystalline g-C₃N₄ (24.60 µmol h^-1). The great improvement of photocatalytic performance can mainly be ascribed to the synergism of improved ordered structure and abundant cyano groups, namely, the efficient transfer and separation of photoinduced charges as well as excellent interfacial hydrogen-generation reaction, respectively. The present work may deliver new strategies to prepare other high-crystalline photocatalysts with great efficiency.

Molecular Self-Assembly of Oxygen Deep-Doped Ultrathin C3N4 with a Built-In Electric Field for Efficient Photocatalytic H2 Evolution

Heteroatom-doped carbon nitride (C₃N₄) with a built-in electric field can reinforce the carrier separation; however, the stability will be greatly reduced due to the loss of surface-doped atoms. Here, molecule self-assembly, as a facile bottom-up approach, is explored for the synthesis and oxygen doping of C₃N₄. The obtained C₃N₄ presents a porous and ultrathin structure and oxygen deep-doping, which generate abundant nitrogen vacancies and a stable built-in electric field. Toward photocatalytic hydrogen evolution, the ultrathin and oxygen deep-doped C₃N₄ exhibits a 3.5-fold higher activity than bulk C₃N₄ under simulated sunlight, and 3.6 times higher stability than the oxygen surface-doped counterpart within five cycles. Femtosecond transient absorption spectroscopy indicates the improved carrier separation, and density functional theory (DFT) calculation reveals the promoted H₂O adsorption and activation under the built-in electric field, which contribute to the excellent photocatalytic performance of oxygen deep-doped ultrathin C₃N₄.

An Inorganic/Organic S-Scheme Heterojunction H2 -Production Photocatalyst and its Charge Transfer Mechanism

Inspired by natural photosynthesis, constructing inorganic/organic heterojunctions is regarded as an effective strategy to design high-efficiency photocatalysts. Herein, a step (S)-scheme heterojunction photocatalyst is prepared by in situ growth of an inorganic semiconductor firmly on an organic semiconductor. A new pyrene-based conjugated polymer, pyrene-alt-triphenylamine (PT), is synthesized via the typical Suzuki-Miyaura reactions, and then employed as a substrate to anchor CdS nanocrystals. The optimized CdS/PT composite, coupling 2 wt% PT with CdS, exhibits a robust H₂ evolution rate of 9.28 mmol h^-1 g^-1 with continuous release of H₂ bubbles, as well as a high apparent quantum efficiency of 24.3%, which is ≈8 times that of pure CdS. The S-scheme charge transfer mechanism between PT and CdS, is systematically demonstrated by photoirradiated Kelvin probe measurement and in situ irradiated X-ray photoelectron spectroscopy analyses. This work provides a protocol for preparing specific S-scheme heterojunction photocatalysts on the basis of inorganic/organic coupling.

Near-Infrared-Responsive Photocatalysts

Broadening the absorption of light to the near-infrared (NIR) region is important in photocatalysis to achieve efficient solar-to-fuel conversion. NIR-responsive photocatalysts that can utilize diffusive solar energy are attractive for alleviating the energy crisis and environmental pollution. Over the past few years, considerable progress on the component and structural design of NIR-responsive photocatalysts have been reported. This study aims to systematically summarize recent progress toward the material design and mechanism optimization of NIR-responsive photocatalysts in this area. Depending on the main strategies for harvesting NIR photons, NIR-responsive photocatalysts can be categorized as direct NIR-light photocatalysts, indirect NIR-light photocatalysts, and photothermal photocatalysts. Furthermore, the construction and application of different NIR-responsive photocatalytic systems are summarized. Conclusions and perspectives are presented to further explore the potential of NIR-responsive photocatalysts in this field.

Ultra-small molybdenum sulfide nanodot-coupled graphitic carbon nitride nanosheets: Trifunctional ammonium tetrathiomolybdate-assisted synthesis and high photocatalytic hydrogen evolution

The preparation of nanoscale molybdenum sulfide (MoS₂)-modified graphitic carbon nitride (g-C₃N₄) nanosheets usually contains complex and multiple-step operations, including the separate synthesis of nanoscale MoS₂ and g-C₃N₄ nanosheet, and their subsequent composite process. To effectively overcome the above drawbacks, herein, a facile one-step trifunctional ammonium tetrathiomolybdate ((NH₄)₂MoS₄)-assisted approach has been designed to produce ultra-small MoS_x nanodot-coupled g-C₃N₄ nanosheet photocatalyst, including the first addition of ammonium chloride (NH₄Cl) and (NH₄)₂MoS₄ into melamine precursors and their following one-step calcination. During high-temperature calcination, except for the promoting generation of the g-C₃N₄ nanosheets by produced ammonia (NH₃) and hydrogen sulfide (H₂S) gases, the above (NH₄)₂MoS₄ decomposition not only can efficiently clip the s-heptazine framework to produce more terminal amino groups and cyano groups, but also can produce ultra-small MoS_x nanodots on the resultant g-C₃N₄ nanosheet surface, resulting in the final production of ultra-small MoS_x nanodot-coupled g-C₃N₄ nanosheets. The resultant MoS_x nanodot-coupled g-C₃N₄ nanosheets evidently exhibit increased photocatalytic hydrogen (H₂)-generation rate, about 8-fold increase to the traditional MoS₂-modified g-C₃N₄ photocatalyst. The increased H₂-generation rate can be mainly attributed to the synergism of MoS_x nanodots and cyano group on the g-C₃N₄ nanosheet surface. The current facile technology could open the sights for the preparation of other high-efficiency photocatalysts.

Ni-MOF-74 derived nickel phosphide and In2O3 form S-scheme heterojunction for efficient hydrogen evolution

The composite structure of Ni2P/In2O3 constructs an S-scheme heterojunction that transfers useless electrons and holes to the composite interface for consumption.The loading of In2O3 further increases the photocatalytic hydrogen production activity.

Crystalline Carbon Nitride Supported Copper Single Atoms for Photocatalytic CO2 Reduction with Nearly 100% CO Selectivity

Single metal atom photocatalysts have received widespread attention due to the rational use of metal resources and maximum atom utilization efficiency. In particular, N-rich amorphous g-C₃N₄ is always used as a support to anchor single metal atoms. However, the enhancement of photocatalytic activity of g-C₃N₄ by introducing a single atom is limited due to the bulk morphology and the excess defects of amorphous g-C₃N₄. Here, we report crystalline g-C₃N₄ nanorod supported copper single atoms by molten salts and the reflux method. The prepared single Cu atoms/crystalline g-C₃N₄ photocatalyst (Cu-CCN) shows highly selective and efficient photocatalytic reduction of CO₂ under the absence of any cocatalyst or sacrificial agent. The introduction of single Cu atoms can be used as the CO₂ adsorption site, thus increasing the adsorption capacity of Cu-CCN samples to CO₂. Theoretical calculation results show that reducing CO₂ to CH₄ on Cu-CCN samples is an entropy-increasing process, whereas reducing CO₂ to CO is an entropy-decreasing process. As a result, the Cu-CCN samples exhibited enhanced photocatalytic CO₂ reduction with nearly 100% selective photocatalytic CO₂ to CO conversion. The mechanism of photocatalytic CO₂ reduction over Cu-CCN samples was proposed based on in situ Fourier transform infrared spectra, X-ray absorption spectroscopy, and density functional theory calculation. This work provides an in-depth understanding of the design of photocatalysts for enhancing active sites of the reactants.

Low-Energy Facets on CdS Allomorph Junctions with Optimal Phase Ratio to Boost Charge Directional Transfer for Photocatalytic H2 Fuel Evolution

Low-energy facets on CdS allomorph junctions with optimal phase ratio are designed to boost charge directional transfer for photocatalytic H₂ fuel evolution. Fermi energy level difference between low-energy facets as driving force promotes electrons directional transfer to hexagonal CdS(102) facet and holes to cubic CdS(111) facet. The optimal allomorphs CdS presents superior photocatalytic H₂ evolution rate of 32.95 mmol g^-1 h^-1 with release in a large amount of visible H₂ bubbles, which is much higher than single-phase CdS with high-energy facets and even supports noble metal photocatalysts. This scientific perspective on low-energy facets of allomorph junctions with optimal phase ratio breaks the long-held view of pursuing high-energy crystal surfaces, which will break the understanding on surface structure crystal facet engineering of photocatalytic materials.