Efficient and long-term photocatalytic H2 evolution stability enabled by Cs2AgBiBr6/MoS2 in aqueous HBr solution

Lead-free Cs₂AgBiBr₆ (CABB) double perovskite as a new-type photocatalytic material alternative to lead halide perovskites holds promise to implement the solar-H₂ conversion, but the interior recombination of photo-generated carriers and thus low photocatalytic hydrogen evolution reaction (HER) rate of CABB restrict its further industrial applications. Herein, we report the composite fabrication of MoS₂/CABB heterostructure for high-efficiency and durable photocatalytic HER by anchoring non-noble MoS₂ onto CABB via a facile dissolution-recrystallization method. The optimized MoS₂/CABB performs a visible-light HER rate of 87.5 μmol h^?1 g^?1 in aqueous HBr solution, ca. 20-fold compared to that of pure CABB (4.3 μmol h^?1 g^?1), and presents a discontinuous 500-h photocatalytic HER stability with no evident loss. The superb performance of MoS₂/CABB can be ascribed to the kinetics-facilitated heterostructure consisting of stable CABB and MoS₂. This work proposes a facile and versatile tactic to construct a low-cost Cs₂AgBiBr₆-based heterostructure for efficient and long-term photocatalytic HER.     

Synergistic enhancement of photocatalytic H2 production by Ni decorated 2D bubble-like carbon nitride

In this paper, a novel 2D bubble-like g-C₃N₄ (B–CN) with a highly porous and crosslinked structure is successfully synthesized via a cost-effective bottom-up process. The as-prepared B–CN photocatalyst delivers a considerably expanded specific surface area and increased active sites. Moreover, the 2D bubble-like structure can afford shortened diffusion paths for both photogenerated charge carriers and reactants. As a result, the photocatalytic H₂ evolution rate of B–CN reached 268.9 μmol g^?1 h^?1, over 5 times more than that of bulk C₃N₄. The Ni ions were further deposited on B–CN as a cocatalyst to enhance the photocatalytic activity. Benefit from the synergy of 2D bubble-like structure and Ni species cocatalyst, recombination of photoinduced charges was greatly inhibited and the hydrogen evolution reaction (HER) was significantly accelerated. The resulted catalyst achieved a dramatically high H₂ evolution rate of 1291 μmol g^?1 h^?1. This work provides an alternative way to synthesize novel porous carbon nitride together with non-noble metal cocatalysts toward enhanced photocatalytic activity for H₂ production.     

Construction of carbon dots modified hollow g-C3N4 spheres via in situ calcination of cyanamide and glucose for highly enhanced visible light photocatalytic hydrogen evolution

In this work, a series of carbon dots (CDs) modified hollow g-C₃N₄ spheres (HCNS-C_x) were constructed via a double in situ approach using cyanamide and glucose as precursors, respectively. As HCNS-C_x was synthesized by one-step in situ thermal polymerization of two precursors, which could make CDs and g-C₃N₄ keep tight connection and increase the separation of the photogenerated electron-hole pairs. The average diameter and wall thickness of the HCNS-C_x are about 355 nm and 55 nm, respectively. Under the visible light irradiation, the H₂ evolution rate (HER) of HCNS-C_1.0 (2322 μmol g^?1 h^?1) was 19 times that of bulk g-C₃N₄ (122 μmol g^?1 h^?1) and 1.8 times that of HCNS without CDs modification (1289 μmol g^?1 h^?1), respectively. And its apparent quantum efficiency is 17.93% at 420 nm. The specific surface area, light absorption capacity, and charge carrier mobility of HCNS-C_x could be dramatically improved due to the introduction of CDs and hollow structures of g-C₃N₄ spheres, resulting in a significant improvement of photocatalytic activity.     

Non-noble-metal Ni nanoparticles modified N-doped g-C3N4 for efficient photocatalytic hydrogen evolution

The use of non-noble-metal to replace precious metal as co-catalyst in solar-driven hydrogen evolution reaction (HER) is important for lowering hydrogen production cost. In this work, nickel metal nanoparticles loaded nitrogen-doped graphite carbon nitride (NiNCN3) was prepared, which significantly enhanced the HER activity of nitrogen-doped graphite carbon nitride. The hydrogen evolution rate of NiNCN3 can reach to 1507 μmol g⁻¹ h⁻¹, much higher than that of 3 wt % Pt/NCN (1055 μmol g⁻¹ h⁻¹). The distinguished photocatalytic performance is due to the accelerated electron transfer efficiency and inhibited photogenerated electron-hole recombination. Our study offers an alternative method to achieve the low-cost and effective noble-metal-free photocatalyst for HER.     

Nanoflower-like Ti3CN@TiO2/CdS heterojunction photocatalyst for efficient photocatalytic water splitting

Solar energy to hydrogen production is an effective way to solve the energy crisis. Here, we report a Ti₃CN@TiO₂/CdS photocatalyst with highly efficient photocatalytic performance. Ti₃CN@TiO₂ materials with nanoflower morphology or lamellar morphology were obtained from Ti₃AlCN by controlling the etching time, and then loaded CdS nanoparticles to improve the photocatalytic efficiency. The physical and chemical properties of the catalyst were characterized by various characterization techniques. Ti₃CN@TiO₂/CdS photocatalyst shows an enhanced photocatalytic activity of 3393.4 μmol g^?1h^?1, much higher than that of CdS and Ti₃CN@TiO₂.^.     

The ZnIn2S4/CdS hollow core-shell nanoheterostructure towards enhanced visible light photocatalytic H2 evolution via bimetallic synergism

The ZnIn₂S₄/CdS hollow core-shell nanoheterostructure with bimetallic synergism is synthesized via a hybrid chemical method. As revealed, the ZnIn₂S₄/CdS hollow core-shell nanoheterostructure (ZnIn₂S₄/CdS-3) exhibits remarkable visible light photocatalytic hydrogen evolution (～5209.43 μmol·g^?1·h^?1, AQE of ～20.26%) than that of single CdS (～40 folds) and single ZnIn₂S₄ (～12 folds), and achieves decent photocatalytic stability (average HER performance of ～5056.80 μmol·g^?1·h^?1), which is mainly ascribed to that, the formed ZnIn₂S₄/CdS heterostructure with appropriate potential gradient and Zn/In bimetallic synergism can improve carrier transportation, including increasing carrier transportation, prolonging lifetime and decreasing recombination, the hollow core-shell nanostructure can provide abundant active sites and increase solar efficiency, while can maintain a photocatalytic stability.     

Promoted interfacial charge transfer by coral-like nickel diselenide for enhanced photocatalytic hydrogen evolution over carbon nitride nanosheet

Seeking an efficient and non-precious co-catalyst for g-C₃N₄ (CN) remains a great demanding to achieve high photocatalytic hydrogen generation performance. Herein, a composite photocatalyst with high efficiency was prepared by modifying CN with coral-like NiSe₂. The optimal hydrogen evolution rate of 643.16 μmol g^?1 h^?1 is from NiSe₂/CN-5 under visible light. Superior light absorption and interfacial charge transfer properties including suppressed photogenerated carrier recombination and efficient separation of photogenerated electron-hole pairs have been observed, which account for the enhanced photocatalytic performance of CN.     

MoS2/Ti3C2 heterostructure for efficient visible-light photocatalytic hydrogen generation

The MoS₂/Ti₃C₂ catalyst with a unique sphere/sheet structure were prepared by hydrothermal method. The MoS₂/Ti₃C₂ heterostructure loading 30% Ti₃C₂ has a maximum hydrogen production rate of 6144.7  μmol g⁻¹ h⁻¹, which are 2.3 times higher than those of the pure MoS₂. The heterostructure maintains a high catalytic activity within 4 cycles. The heterostructure not only effectively reduce the recombination of photogenerated electrons and holes, but also provide more activation sites, which promotes the photocatalytic hydrogen evolution reaction (HER). These works can provide reference for the development of efficient catalysts in photocatalytic hydrogen evolution.     

Additional electron transfer channels of thermostable 0D Cs(Pb: Pt)Br3 perovskite quantum dots /2D accordion-like Ni-MOF nanojunction for photocatalytic H2 evolution

Overcoming the low charge transfer efficiency and poor photothermal stability of halide perovskite quantum dots (QDs) is the booster to achieve photocatalytic applications. In this paper, the Pt²⁺-doped CsPbBr₃ QDs/two-dimensional accordion-like Ni-MOF (CPPB QDs/Ni-MOF) composite was firstly synthesized by fixing the CPPB QDs into the pores of Ni-MOF. Electron separation and transfer efficiency were analyzed by PL spectra and electrochemical data. The photocatalyst exhibited outstanding photocatalytic performance in hydrogen (H₂) evolution. The optimal H₂ evolution efficiency of the composite reached 153.6 μmol h^?1, which was about 9 times than that of pure Ni-MOF and remained 134.8 μmol h^?1 after the cycle test. The splendid efficiency could be benefited from the advantages of 2D layered structure of Ni-MOF and the high charge separation and transmission efficiency of CPPB QDs. Finally, the mechanism of electron migration and additional electron transfer channels between composite interfaces was further demonstrated by density functional theory (DFT) calculations. The present work opens up a novel perspective for photocatalytic applications of doped halide perovskite QDs/Ni-MOF nanocomposites.     

Fabrication of the SnS2/ZnIn2S4 heterojunction for highly efficient visible light photocatalytic H2 evolution

A series of SnS₂/ZnIn₂S₄ (x-SS/ZIS) photocatalysts with different mass ratios of SnS₂ were prepared by a hydrothermal method. The resulted composites were used for photocatalytic hydrogen evolution under visible light excitation. All the SS/ZIS composites exhibited significantly enhanced photocatalytic activity for H₂ evolution. Obviously, the highest H₂ evolution rate of 769 μmol g^?1 h^?1 was observed over 2.5-SS/ZIS, which was approximately 10.5 times that of the ZnIn₂S₄ (73 μmol g^?1 h^?1). The enhanced photocatalytic performance was attributed to the successful construction of SnS₂/ZnIn₂S₄ heterojunctions, leading to rapid charge separation and fast transfer of the photo-generated electrons and holes under light irradiation. On the basis of PL, electrochemical impedance spectroscopy (EIS), photocurrent measurements and the H₂ evolution tests, a plausible photocatalytic mechanism was proposed.     

Fabrication of novel ZnTe-based photocatalyst: Synergistic effect of dye sensitization and bridge engineering for boosting hydrogen evolution over ZnTe

Herein, a novel ZnTe-based photocatalyst is successfully synthesized via a facile combination of water-bath and hydrothermal processes. Morphology characterization and X-ray diffraction analysis reveal that ZnTe presents irregular granular shape and cubic crystal structure. Moreover, Mott-Schottky measurement shows that the conduction band potential of ZnTe is ?0.84 V (vs NHE). With Eosin Y (EY) sensitization, ZnTe exhibits superior photocatalytic hydrogen evolution activity (223.5 μmol g^?1 h^?1). Meanwhile, WC-ZnTe heterojunction is constructed by depositing ZnTe nanoparticles on bulk WC and obtains the optimal H₂ generation rate (559.1 μmol g^?1 h^?1) under EY sensitization. Electrochemical and photoluminescence results further prove that WC as electron bridge could reduce the interfacial resistance and suppress e^?-h⁺ pairs recombination. This study explores the potential application of ZnTe as a newly active photocatalyst in photocatalytic water splitting, and emphasizes the synergistic effect of dye sensitization and bridge engineering.     

Graphite carbon nitride loaded nitrogen-doped carbon and cobalt nanoparticles ternary photocatalyst for enhanced solar-driven hydrogen evolution

In this paper, we designed a composite photocatalytic system in which cobalt nanoparticles (Co NPs) are attached to nitrogen-doped carbon (N-d-C) and co-bonded to the surface of the noted photocatalyst graphite carbon nitride (g-C₃N₄), showing an excellent photocatalytic hydrogen production. The bulk g-C₃N₄ was formed in the first thermal treatment in air using melamine as a precursor. Subsequently, the secondary calcination under N₂ led to the synchronous fabrication of N-d-C/Co NPs and their combination with g-C₃N₄ to form a novel ternary photocatalyst (g-C₃N₄/N-d-C/Co NPs). Co NPs exposed on the surface of the nanomaterials endowed much more reaction sites than g-C₃N₄ for photocatalytic hydrogen production. Meanwhile, the embedded N-d-C provided an additional transfer approach for photocarriers. The as-prepared composite nanomaterials own a relatively high specific surface area of 97.45 m² g^?1 with an average pore size of 3.83 nm. As a result, compared with pristine g-C₃N₄ (～25.35 μmol g^?1 h^?1), the photocatalytic performance was increased by over 10 times (～270.05 μmol g^?1 h^?1). Our work gives a novel approach for highly active g–C₃N₄–based photocatalysts in the field of photocatalysis.     

Novel NiO/RP composite with remarkably enhanced photocatalytic activity for H2 evolution from water

The low photocatalytic activity of red phosphorus (RP) for H₂ production seriously restricts its wide application. In this work, we reported a facile synthesis and remarkable activity improvement of NiO/RP composite for water splitting. As a result, the 3% NiO/RP composite exhibited the highest photocatalytic activity for H₂ production (57.27 μmol g^?1 h^?1), which is 68.56 times higher than that of pure RP (0.82 μmol g^?1 h^?1) under visible light (λ ≥ 420 nm) irradiation. The investigation of photocarriers separation mechanism indicated NiO/RP composite applied a Z-scheme mechanism to promote the photocarriers separation. This is a potential strategy to dramatically enhance the photocatalytic activity of RP for H₂ evolution using transition metal oxide to efficiently separate the photocarriers under light irradiation.     

Oxygen vacancy rich α-MnO2 @B/O-g-C3N4 photocatalyst: A thriving 1D-2D surface interaction effective towards photocatalytic O2 and H2 evolution through Z-scheme charge dynamics

Herein, we have prepared a 1D-2D junction based Oxygen Vacancy rich α-MnO₂@B/O-g-C₃N₄ photocatalyst by using 1D α-MnO₂ nanorods over 2D nanosheets of boron, oxygen co-doped exfoliated graphitic carbon nitride (BOCN). The important feature of the above composite material is the availability of oxygen vacancy as well as the presence of dual oxidation state of Mn (Mn⁴⁺, Mn³⁺) which enhances surface activity as well as chemical reaction output of the material. Among the synthesized materials α-MnO₂@B/O-g-C₃N₄ (MBOCN-20) shows best photocatalytic activity by following Z-Scheme charge dynamics towards water oxidation (295.1 μmol h^?1) and reduction (560.1 μmol h^?1) reactions in presence of methanol (hole scavenger) and AgNO₃ (electron scavenger) as sacrificial agent. However, 44.2 and 86.5 μmol h^?1 of O₂ and H₂ evolution was observed in absence of any sacrificial agent. This analysis will confer a valuable blue-print to construct stimulating photocatalysts to achieve the paramount performance towards photocatalytic water redox reaction.     

Active-center-enriched Ni0.85Se/g-C3N4 S-scheme heterojunction for efficient photocatalytic H2 generation

Photocatalysts with abundant active sites are essential for photocatalytic H₂ evolution from water. Herein, Ni_0.85Se-deposited g-C₃N₄ was obtained by a physical solvent evaporation method. The investigation shows that Ni_0.85Se with unsaturated active Se atoms can significantly improve the photocatalytic activity of g-C₃N₄, and the H₂ production rate of Ni_0.85Se/g-C₃N₄ can reach 8780.3 μmol g^?1 h^?1, which is 3.5 and 92.9 times higher than that of Ni_0.85+xSe/g-C₃N₄ (2497.9 μmol g^?1 h^?1) and pure g-C₃N₄ (94.5 μmol g^?1 h^?1), respectively. This improvement can be attributed to the quick charge transfer between Ni_0.85Se and g-C₃N₄ with S-scheme heterojunction feature based on a series of trapping experiments and photoelectrochemical analysis. Moreover, abundant unsaturated Se atoms could provide more H₂ evolution active sites. This work sheds light on the construction of heterojunctions with abundant active sites for H₂ production.     

Controllable fabrication of 3D porous carbon nitride with ultra-thin nanosheets templated by ionic liquid for highly efficient water splitting

Modifying the texture of carbon nitride to adjust its physicochemical performance is a fascinating method for achieving high photocatalytic activity. Herein, we synthesized 3D porous carbon nitride with ultra-thin nanosheets by using cyanuric acid-melamine supramolecular and ionic liquid as precursor and template, respectively. The ionic liquid adjusts the morphology of materials and induces the carbon residue into the porous channels owing to its incomplete degradation. The 3D porous framework makes carbon nitride reflect the enhanced surface area, exposes adequate reaction sites, and offers a pathway for charge transport. And carbon residue and ultra-thin nanosheets further promote the photogenerated carriers transport and reduce the recombination rate of charge carriers. Consequently, 3D porous carbon nitride with ultra-thin nanosheets exhibit outstanding and stable hydrogen evolution under visible light irradiation. Significantly, as-fabricated sample CN-100 reflects an improved H₂ generation rate, up to 17,028 μmol h^?1 g^?1, which is 12 times higher than that of CN (1412 μmol h^?1 g^?1). The present work offers a unique synthesis strategy to develop the novel photocatalyst with efficient photocatalytic performance.     

Novel 2D Zn-porphyrin metal organic frameworks revived CdS for photocatalysis of hydrogen production

The main challenge of photocatalysis is how to improve the coefficient of utilization and conversion rate for solar energy. Herein, we report a composite photocatalyst related to a novel porphyrin metal organic frameworks (MOFs), in which cadmium sulfide nanoparticles (CdS NPs) are grown in situ on the surface of two-dimensional (2D) zinc porphyrin nanosheets (Zn-TCPP NSs) by hydrothermal method. Interestingly, Zn-TCPP NSs and CdS NPs form a Type II heterojunction structure, which reduces the photogenerated electron-hole recombination rate of CdS. Moreover, in the near-infrared region, the photo-excited electrons generated by Zn-TCPP NSs are transmitted to CdS NPs, so that cadmium sulfide can realize both visible light and near-infrared light for photocatalytic hydrogen production. The Zn-TCPP NSs not only has excellent light absorption capacity, but also has a unique frame design that effectively reduces the recombination rate of photoinduced electron hole pairs, thus improving the conversion rate of solar energy. As expected, the photocatalytic performance of the porphyrin MOFs modified materials is significantly enhanced compared to CdS NPs. The hydrogen production rate of the Pt@CdS NPs/Zn-TCPP NSs(C-Z-T) composite material in the visible light region is about 15.3 mmol g^?1 h^?1, which is 11 times for Pt@CdS NPs. Furthermore, the Pt@CdS NPs/Zn-TCPP NSs(C-Z-T) also has a considerable hydrogen production rate in the near-infrared region, such as 200 μmol g^?1 h^?1 at 600 nm, 90 μmol g^?1 h^?1 at 765 nm and 20 μmol g^?1 h^?1 at > 800 nm.     

Photocatalytic hydrogen evolution assisted by aqueous (waste)biomass under simulated solar light: Oxidized g-C3N4 vs. P25 titanium dioxide

Oxidized graphitic carbon nitride (o-g-C₃N₄) and Evonik AEROXIDE^® P25 TiO₂ were compared for lab-scale photocatalytic H₂ evolution from aqueous sacrificial biomass-derivatives, under simulated solar light. Experiments in aqueous starch using Pt or Cu–Ni as the co-catalysts indicated that H₂ production is affected by co-catalyst type and loading, with the greatest hydrogen evolution rates (HER) up to 453 and 806 μmol g⁻¹ h⁻¹ using TiO₂ coupled with 3 wt% Cu–Ni or 0.5 wt% Pt, respectively. Despite the lower surface area, o-g-C₃N₄ gave HERs up to 168 and 593 μmol g⁻¹ h⁻¹ coupled with 3 wt% Cu–Ni or 3 wt% Pt. From mono- and di-saccharide solutions, H₂ evolution was in the range 504–1170 μmol g⁻¹ h⁻¹ for Pt/TiO₂ and 339–912 μmol g⁻¹ h⁻¹ for Cu–Ni/TiO₂, respectively; o-g-C₃N₄ was efficient as well, providing HERs of 90–610 μmol g⁻¹ h⁻¹. The semiconductors were tested in sugar-rich wastewaters obtaining HERs up to 286 μmol g⁻¹ h⁻¹. Although HERs were lower compared to Pt/TiO₂, a cheap, eco-friendly and non-nanometric catalyst such as o-g-C₃N₄, coupled to non-noble metals, provided a more sustainable H₂ evolution.     

Hollow heterostructure CoS/CdS photocatalysts with enhanced charge transfer for photocatalytic hydrogen production from seawater

In recent years, there have been many studies on photocatalytic water splitting, but there are still few high-efficiency photocatalysts for photocatalytic seawater splitting. In this study, a series of hollow Co sulphide-supported CdS catalyst (H–CoS/CdS) composite photocatalysts were prepared by loading CdS onto the surface of H–CoS, which can be used for efficient H₂ production in pure water and simulated seawater. The heterojunction H–CoS/CdS exhibited H₂ production of 572.4 μmol g^?1 (4 h) from simulated seawater, which is 97.7 and 2.96 times those of H–CoS and CdS, respectively. The h-CoS cocatalyst extended the light absorption range of CdS, improved the chemical stability, and significantly enhances the charge separation efficiency. This study provides guidance for the reasonable design of a photocatalytic seawater-based H₂ production catalyst with high efficiency and low cost.     

Hydrothermally decorated robust bimetallic sulfides with heterojunction interfaces for efficient hydrogen generation

Bimetallic semiconductor metal sulphides are promising for harnessing light energy. In this report, a hydrothermally decorated robust ZnO/ZnS/NiS (ZSN) ternary composite was synthesized and employed in photocatalytic H₂ generation. The structurally defined ZnS/NiS on ZnO nanorods have been observed as efficient visible light driven proton reduction system due to its multiple accessible active sites. Benefitting from the synergetic effects between highly active, ZnS and NiS, the ternary composite ZSN exhibited significantly improved performance of H₂ generation with a rate of 8471 μmol g^?1h^?1 and AQE of ～5.5% under solar irradiation. This design in ZSN enables effective transfer of electrons from ZnS to NiS active sites leading to 29 times and 3.4 times increase in hydrogen production and current density when compared with pristine ZnO photocatalyst, respectively. The photocurrent density and transient photocurrent curve show rapid charge transfer as well as the unique electron transfer paths through the contact surface, resulting in efficient charge separation. DFT and photoelectrochemical studies reveal higher HER activity due to the augmented electric field at the dual-interfaces between NiS and ZS complex.