Efficient Photocatalysts For Hydrogen Evolution Research Articles

Efficient photocatalytic hydrogen production via single-atom Pt anchored hydrogen-bonded organic frameworks

Constructing single-atom catalysts (SACs) using organic porous framework materials as supports presents a promising approach for developing highly efficient photocatalysts for hydrogen evolution. However, the fabrication of SACs that are both highly stable and active poses a significant challenge, particularly in the precise anchoring of metal single atoms. In this study, we utilized 1,3,6,8-tetra (p-methyl benzoate) pyrene as a ligand to synthesize pyrene-based hydrogen-bonded organic frameworks (denoted as PFC-1) through a self-assembly approach. Subsequently, a liquid-phase photoreduction process was employed to deposit noble metal platinum (Pt) onto PFC-1, resulting in the fabrication of SACs (PFC-1@Pt). Characterization results confirmed that Pt existed in a monatomic state, anchored through PtC and PtO coordination bonds with PFC-1. Serving as electron capture and separation centers, the Pt single atoms effectively suppressed electron-hole recombination, thereby prolonging carrier lifetimes. Consequently, the PFC-1@Pt SAC exhibited efficient hydrogen evolution performance with a rate of 2202.5 μmol g−1 h−1 and maintained photocatalytic activity for over 40 h. Our findings provide a systematic approach for developing efficient and stable SACs based on HOFs, expanding the potential applications of HOF materials in photocatalysis.

A novel hexagonal prism of Zr-based MOF@ZnIn2S4 core−shell nanorod as an efficient photocatalyst for hydrogen evolution

Photocatalytic water splitting is a commonly used pathway for hydrogen (H2) production, and it is crucial to develop highly active ZnIn2S4 (ZIS)-based photocatalytic systems. In recent years, metal-organic frameworks (MOFs) are also of great interest in the fields of energy production and environmental remediation. Therefore, this study primarily focuses on the fabrication of a series of heterojunction hexagonal prism-shaped Zr-based MOF@ZIS core-shell nanorods through a simple solvothermal method, in which ZIS nanosheets are highly distributed on the surface of the Zr-based MOF (NU-1000). The photocatalytic activities of the resulting materials were evaluated under visible light illumination (λ ≥ 400 nm) by combining different contents of NU-1000 with ZIS. The H2 evolution results demonstrate that the optimal content of NU-1000 corresponds to a photocatalytic H2 production rate of 8.53 mmol g−1 h−1, which is 5.3 times higher than that of pure ZIS. The enhanced photocatalytic activity of the NU-1000@ZIS (NUZ) heterojunction can be attributed to the incorporation of the NU-1000, which provides abundant active sites due to its larger specific surface area. Additionally, the well-matched band structure between the NU-1000 and ZIS is beneficial to efficiently transfer and separate the photogenerated charge carriers. Furthermore, the NUZ core-shell nanorods exhibit excellent stability, offering a new approach for the fabrication of composite photocatalysts by combining MOF-based and ZIS in the field of photocatalytic H2 production.

Comparative Study on the Effect of Terthienyl-diphenylstyrene Type Organic Photocatalysts for Efficient Hydrogen Evolution

Comparative Study on the Effect of Terthienyl-diphenylstyrene Type Organic Photocatalysts for Efficient Hydrogen Evolution

Photocharging-activated photocatalysis for hydrogen production in CdS@CdxPb1−xS core-shell nanoparticles

The CdS@CdxPb1−xS core–shell photocatalyst was synthesized through cation exchange and demonstrated significant photocatalytic hydrogen production. Initially, the catalyst was inactive due to the formation of an unfavourable Type I heterojunction. However, under continued illumination, electron accumulation in the CdxPb1−xS shell led to electron repulsion, triggering a structural transition from a film-like morphology to quantum dots. This transition resulted in the formation of a Type II heterojunction between the CdS and PbS components, boosting hydrogen production by 400 % compared to CdS nanoparticles. The reversible structural transformation and stable performance over multiple cycles highlight the potential of CdS@CdxPb1−xS nanoparticles as a highly efficient photocatalyst for hydrogen evolution.

Interfacial chemical bonds and sulfur vacancies synergistically modulated charge transfer in ZnIn2S4/MoO2-C Ohmic-junction photocatalyst for efficient hydrogen evolution

The construction of an Ohmic contact with a strong built-in electric field is crucial for the photocatalytic hydrogen evolution performance. However, consciously modulating Ohmic contacts to facilitate charge transfer remains very difficult. Herein, a sulfur vacancies-rich ZnIn2S4/MoO2-C Ohmic contact structure was synthesized by solvothermal method. Experimental results and DFT calculations indicated that the structure of MoO2-C changes under high temperature and pressure conditions, leading to the formation of interfacial Mo-S bonds with sulfur-vacancy-rich ZnIn2S4 in close contact. Importantly, the electronic structure of the Ohmic junction was synergistically modulated by interfacial chemical bonds and sulfur vacancies, creating a strong built-in electric field that effectively facilitated charge transfer and exciton dissociation at the interface. The optimized ZnIn2S4/MoO2-C composite exhibited a photocatalytic hydrogen evolution rate of 59.9 µmol h−1, which was 12 times and 4.7 times higher than that of ZnIn2S4 without sulfur vacancies and with sulfur vacancies, respectively. This work presented a novel method of synergistically modulating charge transfer in Ohmic junctions, promising improved photocatalytic performance.

Symmetry‐breaking of Dibenzo[b,d]thiophene Sulfone Enhancing Polaron Generation for Boosted Photocatalytic Hydrogen Evolution

AbstractThe current bottleneck in the development of efficient photocatalysts for hydrogen evolution is the limited availability of high‐performance acceptor units. Over the past nine years, dibenzo[b,d]thiophene sulfone (DBS) has been the preferred choice for the acceptor unit. Despite extensive exploration of alternative structures as potential replacements for DBS, a superior substitute remains elusive. In this study, a symmetry‐breaking strategy was employed on DBS to develop a novel acceptor unit, BBTT‐1SO. The asymmetric structure of BBTT‐1SO proved beneficial for increasing multiple moment and polarizability. BBTT‐1SO‐containing polymers showed higher efficiencies for hydrogen evolution than their DBS‐containing counterparts by up to 166 %. PBBTT‐1SO exhibited an excellent hydrogen evolution rate (HER) of 222.03 mmol g−1 h−1 and an apparent quantum yield of 27.5 % at 500 nm. Transient spectroscopic studies indicated that the BBTT‐1SO‐based polymers facilitated electron polaron formation, which explains their superior HERs. PBBTT‐1SO also showed 14 % higher HER in natural seawater splitting than that in deionized water splitting. Molecular dynamics simulations highlighted the enhanced water‐PBBTT‐1SO polymer interactions in salt‐containing solutions. This study presents a pioneering example of a substitute acceptor unit for DBS in the construction of high‐performance photocatalysts for hydrogen evolution.

Symmetry-breaking of Dibenzo[b,d]thiophene Sulfone Enhancing Polaron Generation for Boosted Photocatalytic Hydrogen Evolution.

The current bottleneck in the development of efficient photocatalysts for hydrogen evolution is the limited availability of high-performance acceptor units. Over the past nine years, dibenzo[b,d]thiophene sulfone (DBS) has been the preferred choice for the acceptor unit. Despite extensive exploration of alternative structures as potential replacements for DBS, a superior substitute remains elusive. In this study, a symmetry-breaking strategy was employed on DBS to develop a novel acceptor unit, BBTT-1SO. The asymmetric structure of BBTT-1SO proved beneficial for increasing multiple moment and polarizability. BBTT-1SO-containing polymers showed higher efficiencies for hydrogen evolution than their DBS-containing counterparts by up to 166 %. PBBTT-1SO exhibited an excellent hydrogen evolution rate (HER) of 222.03 mmol g-1 h-1 and an apparent quantum yield of 27.5 % at 500 nm. Transient spectroscopic studies indicated that the BBTT-1SO-based polymers facilitated electron polaron formation, which explains their superior HERs. PBBTT-1SO also showed 14 % higher HER in natural seawater splitting than that in deionized water splitting. Molecular dynamics simulations highlighted the enhanced water-PBBTT-1SO polymer interactions in salt-containing solutions. This study presents a pioneering example of a substitute acceptor unit for DBS in the construction of high-performance photocatalysts for hydrogen evolution.

Overcoming small-bandgap charge recombination in visible and NIR-light-driven hydrogen evolution by engineering the polymer photocatalyst structure

Designing an organic polymer photocatalyst for efficient hydrogen evolution with visible and near-infrared (NIR) light activity is still a major challenge. Unlike the common behavior of gradually increasing the charge recombination while shrinking the bandgap, we present here a series of polymer nanoparticles (Pdots) based on ITIC and BTIC units with different π-linkers between the acceptor-donor-acceptor (A-D-A) repeated moieties of the polymer. These polymers act as an efficient single polymer photocatalyst for H2 evolution under both visible and NIR light, without combining or hybridizing with other materials. Importantly, the difluorothiophene (ThF) π-linker facilitates the charge transfer between acceptors of different repeated moieties (A-D-A-(π-Linker)-A-D-A), leading to the enhancement of charge separation between D and A. As a result, the PITIC-ThF Pdots exhibit superior hydrogen evolution rates of 279 µmol/h and 20.5 µmol/h with visible (>420 nm) and NIR (>780 nm) light irradiation, respectively. Furthermore, PITIC-ThF Pdots exhibit a promising apparent quantum yield (AQY) at 700 nm (4.76%).

Twinned crystal Cd0.9Zn0.1S/MoO3 nanorod S-scheme heterojunctions as promising photocatalysts for efficient hydrogen evolution.

Leveraging solar energy through photocatalytic hydrogen production from water stands out as one of the most promising approaches to address the energy and environmental challenges. The choice of catalyst profoundly influences the outcomes of photocatalytic reactions, and constructing heterojunctions has emerged as a widely applied strategy to overcome the limitations associated with single-phase photocatalysts. MoO3, renowned for its high chemical stability, encounters issues such as low photocatalytic efficiency and fast recombination of photogenerated electrons and holes. To tackle these challenges, the morphology of MoO3 has been controlled to form nanorods, simultaneously suppressing the aggregation of the catalyst and increasing the number of surface-active sites. Moreover, to facilitate the separation of photogenerated charge carriers, Cd0.9Zn0.1S nanoparticles with a twin crystal structure are deposited on the surface of MoO3, establishing an S-scheme heterojunction. Experimental findings demonstrate that the synergistic effects arising from the well-defined morphology and interface interactions extend the absorption range to visible light response, improve charge transfer activity, and prolong the lifetime of charge carriers. Consequently, Cd0.9Zn0.1S/MoO3 S-scheme heterojunctions exhibit outstanding photocatalytic hydrogen production performance (3909.79 μmol g-1 h-1) under visible light irradiation, surpassing that of MoO3 by nearly nine fold.

Fabrication of ZnMn2O4@ZnIn2S4 ball-in-ball hollow microspheres as efficient photocatalysts for hydrogen evolution

This study describes the preparation of ZnMn2O4@ZnIn2S4 ball-in-ball hollow microspheres as photocatalysts. Remarkably, the PHE rate of 10% ZnMn2O4@ZnIn2S4 can reach 11.12 mmol g−1 h−1, roughly 4.9 times greater than that of pure ZnIn2S4.

Boosting the water splitting and hydrogen production of S-scheme fabricated porous g-C3N4 modified with CuO

In response to the growing demand for sustainable hydrogen generation, particularly through solar energy conversion, this study focuses on the development of an S-scheme CuO/porous g-C3N4 (CuO/pCN) heterojunction nanocomposite for enhanced photocatalytic H2 evolution via water splitting under visible light. Coupling CuO with porous CN yields a remarkable H2 generation of 30 μmol/gh, about 5.29 times higher than CN (5.67 μmol/gh) and 2.78 times higher than pCN (10.78 μmol/gh). The superior performance of CuO/pCN is attributed to its highly porous structure with a large surface area (33.8 m2/g), which benefits the exposure of active sites, while a narrow band gap enhances photon absorption and utilization. Additionally, the formation of S-scheme heterojunction promotes more efficient separation of photoinduced charge carriers. CuO modification significantly enhances photocatalytic activity, contributing to efficient H2 production. A thorough investigation into crystal structure, surface morphology, and elemental composition elucidates characteristics responsible for heightened photochemical catalysis. The S-scheme heterojunction creation extends visible light absorption, achieving excellent photo-redox ability and mitigating photoinduced electron-hole recombination. In conclusion, this research presents a sustainable approach to efficient photocatalysts for hydrogen evolution, contributing to renewable energy production.

Electronic coupling between metallic Ni and VN nanoparticles enables g-C3N4 nanosheet as an efficient photocatalyst for hydrogen evolution

Developing highly efficient hydrogen evolution cocatalysts is of great significance for semiconductor photocatalysts toward the large-scale conversion of solar light energy into clean hydrogen fuel. Herein, a novel Ni/VN hetero-nanosheets is reported for the first time, as precious metal-free co-catalyst for g-C3N4, and the electronic coupling between Ni and VN greatly promotes the photocatalytic hydrogen production activity of g-C3N4 nanosheet (CNNS) under visible-light irradiation. As expected, CNNS with 3 wt% Ni/VN (CNNS/Ni/VN) exhibits excellent photocatalytic activity with hydrogen production rates are as high as 417.1 μmol h−1g−1. In addition, CNNS/Ni/VN has excellent cyclic hydrogen production stability for 24 h. This excellent performance is attributed to the strong electron coupling between Ni and VN. Therefore, the Ni/VN cocatalysts will open a newfangled way for powerful solar-fuel production.

Graphdiyne (g-CnH2n-2) boosting electron transfer over rational design and construction of CuI/Ni-MOF photocatalyst for efficient hydrogen evolution

A CuI-graphdiyne/Ni-MOF ternary system was successfully constructed. Intially, CuI-graphdiyne was obtained by growth of GDY on the surface of CuI. Subequently, the CuI-graphdiyne was immobilized onto the surface of Ni-MOF using a simple physical stirring method. This, immobilization approach effectively reducing the accumulation of CuI-graphdiyne and increased the number of active sites for hydrogen evolution. Furthermore, a combination of various characterization techniques and energy band structures analysis was employed to propose the photocatalytic reaction mechanism between CuI and Ni-MOF. The proposed mechanism involves a Z-scheme heterojunction and suggests that the combination of CuI and Ni-MOF enhances the overall redox ability of the composite catalyst. By comparing CuI/Ni-MOF with CuI-graphdiyne/Ni-MOF, it was observed that the presence of graphdiyne as an electron-rich layer on CuI enhances the photocatalytic performance of CuI. Additionally, it facilitates electron transport between CuI and Ni-MOF, thereby improving the efficiency of photogenerated electron-hole complex separation. This experimental study provides valuable insight into the utilization of graphdiyne for enhancing transport in heterojunction.

Construction of novel photocatalysts for efficient hydrogen evolution: The key role of natural halloysite nanotubes

Hydrogen (H2) evolution by photocatalytic water splitting is a potential strategy to solve worldwide energy shortage. Sulfide nanocatalysts showed great potential for H2 evolution, but suffered from low charge separation efficiency and easy agglomeration. In this work, ZnIn2S4 (ZIS) nanoflowers were anchored onto the surface of halloysite nanotubes (HNTs) modified by ethylenediaminetetraacetic acid (EDTA). Photocatalyst 3ZnIn2S4-HNTs/EDTA3 (3ZIS-HNTs/E3) displayed the optimum H2 evolution rate of 10.4 mmol·g−1·h−1, being 3.4 times as that of the original ZIS. Moreover, 3ZIS-HNTs/E3 presented satisfied property in the photocatalytic hydrogenation reaction of 4-nitrophenol to produce 4-aminophenol. HNTs as substrates not only hindered the growth and agglomeration of ZIS, but also induced more S vacancies in ZIS. The production of Schottky junctions between ZIS and Pt, the high utilization of light energy in tubular HNTs, and the trapping effect of EDTA for photogenerated h+ were all favorable for enhancing the catalytic property. The density functional theory (DFT) calculations showed that 3ZIS-HNTs/E3 with more S vacancies had the lowest adsorption energy and the most appropriate ΔGH* for H* to enhance the H2 evolution efficiency, which was consistent with the experimental catalytic results. This study contributes a novel thought for synthesizing composites on the basis of natural minerals for taking part in and enhancing the catalytic performance.

Pyrene‐ and Bipyridine‐based Covalent Triazine Framework as Versatile Platform for Photocatalytic Solar Fuels Production**

AbstractThe ability to molecularly engineer materials is a powerful tool toward increasingly performing heterogeneous catalysts. Porous organic polymers stand out as photocatalysts due to their high chemical stability, outstanding optoelectronic properties and their easy and tunable syntheses. In photocatalysis, the insertion of photosensitizing π‐extended molecules into molecularly well‐defined donor‐acceptor junctions is supposed to increase the catalytic activity, but yet remain experimentally underdeveloped. This study presents a pyrene‐based Covalent Triazine Framework (CTF) synthesized through a polycondensation approach, which was designed to contain a molecularly‐defined pyrene‐triazine‐bipyridine donor‐acceptor‐acceptor triad as the repetition unit of the CTF. The CTF is an efficient photocatalyst for hydrogen evolution from water reaching a significant production rate of 61.5 mmolH2/h/gcat. Moreover, the same CTF can easily be used as porous macroligand for an organometallic Rh complex to efficiently catalyze the carbon dioxide photoreduction into formic acid under visible light.

Stabilization and Performance Enhancement Strategies for Halide Perovskite Photocatalysts.

Solar-energy-powered photocatalytic fuel production and chemical synthesis are widely recognized as viable technological solutions for a sustainable energy future. However, the requirement of high-performance photocatalysts is a major bottleneck. Halide perovskites, a category of diversified semiconductor materials with suitable energy-band-enabled high-light-utilization efficiencies, exceptionally long charge-carrier-diffusion-length-facilitated charge transport, and readily tailorable compositional, structural, and morphological properties, have emerged as a new class of photocatalysts for efficient hydrogen evolution, CO2 reduction, and various organic synthesis reactions. Despite the noticeable progress, the development of high-performance halide perovskite photocatalysts (HPPs) is still hindered by several key challenges: the strong ionic nature and high hydrolysis tendency induce instability and an unsatisfactory activity due to the need for a coactive component to realize redox processes. Herein, the recently developed advanced strategies to enhance the stability and photocatalytic activity of HPPs are comprehensively reviewed. The widely applicable stability enhancement strategies are first articulated, and the activity improvement strategies for fuel production and chemical synthesis are then explored. Finally, the challenges and future perspectives associated with the application of HPPs in efficient production of fuels and value-added chemicals are presented, indicating the irreplaceable role of the HPPs in the field of photocatalysis.

Two-Dimensional Ultrathin Graphic Carbon Nitrides with Extended π-Conjugation as Extraordinary Efficient Hydrogen Evolution Photocatalyst.

Construction of 2D graphic carbon nitrides (g-CNx ) with wide visible light adsorption range and high charge separation efficiency concurrently is of great urgent demand and still very challenging for developing highly efficient photocatalysts for hydrogen evolution. To achieve this goal, a two-step pyrolytic strategy has been applied here to create ultrathin 2D g-CNx with extended the π-conjugation. It is experimentally proven that the extension of π-conjugation in g-CNx is not only beneficial to narrowing the bandgap, but also improving the charge separation efficiency of the g-CNx . As an integral result, extraordinary apparent quantum efficiencies (AQEs) of 57.3% and 7.0% at short (380nm) and long (520nm) wavelength, respectively, are achieved. The formation process of the extended π-conjugated structures in the ultrathin 2D g-CNx has been investigated using XRD, FT-IR, Raman, XPS, and EPR. Additionally, it has been illustrated that the two-step pyrolytic strategy is critical for creating ultrathin g-CNx nanosheets with extended π-conjugation by control experiments. This work shows a feasible and effective strategy to simultaneously expand the light adsorption range, enhance charge carrier mobility and depress electron-hole recombination of g-CNx for high-efficient photocatalytic hydrogen evolution.

Integrating electronic structure regulation and dynamic active sites construction on NixCd1-xS-Ni0 photocatalyst for efficient hydrogen evolution

Regulating electronic structure and enriching active sites of photocatalysts are effective strategies to promote hydrogen evolution. Herein, a unique NixCd1-xS-Ni0 photocatalyst, including the surface nickel (Ni) doping and atomic Ni0 anchoring sites, is successfully prepared by Ni2+ ions exchange reaction (Ni2++ CdS → NixCd1-xS) and in-situ photo-induction of Ni0(Ni2++NixCd1-xS→hνNixCd1-xS-Ni0), respectively. As to Ni doping, the Ni replaced cadmium (Cd) atoms introduce hybridized states around the Fermi level, modulating the electronic structure of adjacent S atoms and optimizing the photocatalytic activity of sulfur (S) atoms. Besides, photogenerated Ni0 atoms, anchored on unsaturated S atoms, act as charge transfer bridges to reduce Ni2+ ions in the solution to Ni clusters (NixCd1-xS-Ni0→ne-NixCd1-xS-Ni). Subsequently, the displacement reaction of Ni clusters with protons (H+) spontaneously proceeds to produce hydrogen (H2) in an acidic solution (NixCd1-xS-Ni→2H+H2↑+Ni2++NixCd1-xS-Ni0). The equilibrium of photo-deposition/dissolution of Ni clusters realizes the construction of dynamic active sites, providing sustainable reaction centers and enhancing surface redox kinetics. The NixCd1-xS-Ni0 exhibits a high hydrogen evolution rate of 428 mmol·h−1·g−1 with a quantum efficiency of 75.6 % at 420 nm. This work provides the optimal S electronic structure for photocatalytic H2 evolution and constructs dynamic Ni clusters for chemical replacement reaction. This work provides the optimal S electronic structure for photocatalytic H2 evolution and constructs dynamic Ni clusters for displacement reaction, opening a dual pathway for efficient water reduction.

Adenine-functionalized conjugated polymer as an efficient photocatalyst for hydrogen evolution from water

Conjugated polymers have emerged as a promising class of organic photocatalysts for photocatalytic hydrogen evolution from water splitting due to their adjustable chemical structures and electronic properties. However, developing highly efficient organic polymer photocatalysts with high photocatalytic activity for hydrogen evolution remains a significant challenge. Herein, we present an efficient approach to enhance the photocatalytic performance of linear conjugated polymers by modifying the surface chemistry via introducing a hydrophilic adenine group into the side chain. The adenine unit with five nitrogen atoms could enhance the interaction between the surface of polymer photocatalyst and water molecules through the formation of hydrogen bonding, which improves the hydrophilicity and dispersity of the resulting polymer photocatalyst in the photocatalytic reaction solution. In addition, the strong electron-donating ability of adenine group with plentiful nitrogen atoms could promote the separation of light-induced electrons and holes. As a result, the adenine-functionalized conjugated polymer PF6A-DBTO2 shows a high photocatalytic activity with a hydrogen evolution rate (HER) of 25.21 mmol g−1 h−1 under UV-Vis light irradiation, which is much higher than that of its counterpart polymer PF6-DBTO2 without the adenine group (6.53 mmol g−1 h−1). More importantly, PF6A-DBTO2 without addition of a Pt co-catalyst also exhibits an impressive HER of 21.93 mmol g−1 h−1 under visible light (λ > 420 nm). This work highlights that it is an efficient strategy to improve the photocatalytic activity of conjugated polymer photocatalysts by the modification of surface chemistry.

Interfacial microenvironment-regulated cascade charge transport in Co6Mo6C2-MoO2-CoNC@ZnIn2S4 photocatalyst for efficient hydrogen evolution

High-quality interfacial coupling can effectively boost photogenerated charge separation/transfer efficiency. Herein, we develop a multicomponent photocatalyst, Co6Mo6C2-MoO2-CoNC@ZnIn2S4 (CMN@Z), featuring directional and swift carrier transfer ability through interfacial microenvironment modulation. The distinctive CMN@Z displays a ten-times enhanced photocatalytic H2-production performance of 4728 μmol·g−1·h−1 than pure ZIS, accompanied by optimized apparent quantum efficiency of 25.06 % at 420 nm. Typically, the well-tuned Schottky barrier readily balances its bifunctionality in rectifying effect and powerful photogenerated electron extraction impetus. Moreover, the gradient work function variation enables the interfacial potential as a robust driving force to expedite charge transfer. Therefore, the resulting cascade charge channel and intimate interfacial contact endow CMN@Z photocatalyst with optimized H2-production performance by virtue of high-efficiency carrier spatial separation and utilization. Our work deeply explores the role of multiple interfacial in coupling photocatalytic systems, which offers new insight into the rational design of cascade photocatalysts.