Photocatalyst For Hydrogen Evolution Research Articles

Substituent Regulating Porphyrin Derivatives for Efficient Photocatalytic Hydrogen Evolution

AbstractPorphyrin and its derivatives have been seen as a type of potential organic photocatalyst for photocatalytic hydrogen evolution. Substituent regulation as a simple method can effectively regulate the photoelectric characteristic of organic semiconductors. Herein, we designed three porphyrin derivatives attached with different substituents (PP‐NH2, PP‐OH and PP‐COOH). Through a facile substituent optimization strategy, the photoelectric properties of these porphyrin derivatives show an obvious difference, which leads an optimized photocatalytic hydrogen evolution efficiency. The porphyrin derivative with carboxyl presents a reduced impedance, and a better charge separation. Compared to the amino group, PP‐COOH with carboxyl, achieved a high hydrogen evolution rate of 2.20 mmol g−1 h−1 (over 20 times than that of PP‐NH2). Moreover, enhanced stability was observed in PP‐COOH rather than PP‐OH, because of the lower HOMO energy level. And the ionization of carboxyl in water negatively charges the porphyrin derivatives and forms a relatively stable sol. This result further increases the operation stability of PP‐COOH, during photocatalytic hydrogen evolution. This study presents a promising design strategy for long‐lifetime photocatalysts for hydrogen evolution.

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.

Elevating photocatalytic H2 evolution over ZnIn2S4@Au@Cd0.7Zn0.3S multilayer nanotubes via Au-mediating H–S antibonding-orbital occupancy

Metal sulfides have been considered as an important category of photocatalysts for photocatalytic hydrogen evolution because of their low cost, simple preparation process and abundance of active sites. However, the atomic hydrogen is generally adsorbed on the sulfide photocatalysts to form strong H–S bond, which impedes the release of generated H2 molecules from the photocatalyst surface, severely limiting the H2 evolution efficiency. To address this issue, herein we have designed an interesting type of ZnIn2S4@Au@Cd0.7Zn0.3S (ZIS@Au@CZS) multilayer nanotubes with Au medium sandwiched between inner CZS layer and outer ZIS layer. The Au medium serves as the electron mediator to provide free electrons to fill the H–S antibonding orbitals in CZS and ZIS; this process decreases the adsorption capability of the S sites towards atomic hydrogen, thus facilitating the release of generated H2 molecules. This study provides an important guidance for modifying the photocatalysts to maximize their photocatalytic H2 evolution.

Template-synthesized CdWO4/Cd0.5Zn0.5S hollow microsphere photocatalyst for high-efficient hydrogen evolution under visible light

Photocatalytic water splitting for hydrogen production is a promising strategy for renewable energy. While Cd1-XZnXS catalysts display high photocatalytic hydrogen evolution efficiency in pure water, they are limited by severe photocorrosion and rapid recombination of electron–hole pairs. In this study, HGM (hollow glass microspheres) was used as the support template, Cd0.5Zn0.5S and CdWO4 were successively coated on the template by hydrothermal method. The tightly packed heterojunction interface between the coatings ensures efficient electron transport and suppresses the recombination of electron-hole pairs. Under visible light irradiation, when the theoretical mass ratio of Cd0.5Zn0.5S to CdWO4 is 4:1, the Cd0.5Zn0.5S/CdWO4-25% hollow microsphere photocatalyst exhibits the highest hydrogen evolution rate, reaching 41.40 mmol g−1 h−1, which is approximately 3.4 times higher than the hydrogen evolution rate of pure Cd0.5Zn0.5S (12.31 mmol g−1 h−1). This research provides a novel approach for the design and synthesis of efficient and stable photocatalysts.

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.

Heterointerface engineering in mesoporous g-C3N4@MnFe2O4 photocatalysts for superior hydrogen (H2) evolution

Surfaces and interfaces play a pivotal role in heterostructures-based photocatalysts, which regulate the transfer, separation, and migration of photogenerated charge carriers. In this study, p-type MnFe2O4 nanoparticles (NPs) with complementary band structures were purposefully integrated with n-type porous g-C3N4 nanosheets (NSs) through precise interface engineering. The synergies in the g-C3N4@MnFe2O4 nanocomposites (NCs), leading to performance enhancement and functionalities, arise from their optimized mass fractions within the composite. The heterojunction interface formed in NCs possesses uniformly distributed mesopores (<4 nm), abundant active sites, and a high specific surface area (116 m2/g). Mesoporous heterojunctions improve photocatalytic activity by promoting the transfer of photogenerated electrons and holes to the photocatalyst surface. Notably, the optimized NCs, containing 20 wt% MnFe2O4, display the highest hydrogen evolution rate of 3.17 mmol g⁻¹ h⁻¹ (with methanol) and 5.77 mmol g⁻¹ h⁻¹ (with triethanolamine), which is many folds higher than bare MnFe2O4 and porous g-C3N4, using 1.0 wt.% of Pt as co-catalyst. The enhanced performance is corroborated by the efficient separation of photoinduced charge carriers, facilitated by an induced internal electric field arising from the Fermi level differences between the semiconductors. This study provides new insights into the advantages of designing and constructing mesoporous Z-scheme heterojunction photocatalysts for hydrogen evolution.

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

Highly efficient dual-functional Zn0.6Cd0.4S photocatalyst for dye removal and Pt co-catalyzed hydrogen evolution

Designing an efficient and stable dual-functional photocatalyst for organic dyes removal and hydrogen (H2) evolution has emerged as a crucial research direction to address the pressing issues of severe environmental pollution and the energy crisis. In this work, Zn(1-x)CdxS solid solutions were prepared by a one-step hydrothermal method, with variations in both the pH of the precursor solutions and the molar ratios of Cd/Zn. The as-prepared Zn(1-x)CdxS solid solutions featured small crystallite size and controllable band structure, which was conducive to photocatalysis. When the pH of the precursor solution was 8 and the molar ratio of Cd/Zn was 0.4:0.6, the resulting Zn0.6Cd0.4S-8 solid solution exhibited remarkable photocatalytic activities towards RhB (94.6 %), MO (54.9 %) and MB (89.3 %). Furthermore, the H2 evolution rate of Zn0.6Cd0.4S-8 solid solution modified with Pt can reach 7.01 mmol·g−1·h−1 with 0.5 M Na2S-Na2SO3 as sacrificial agent. Zn0.6Cd0.4S-8 solid solution maintained good photocatalytic stability and the apparent quantum yield (AQY) was 9.16 %. Moreover, the possible photocatalytic mechanism was also proposed.

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.

Cu surface plasmon resonance promoted charge transfer in S-scheme system enhanced visible light photocatalytic hydrogen evolution

Reasonably constructing nanocomposite photocatalysts with fast charge transfer and broad solar response capabilities is significant for efficiently converting solar energy into chemical energy. Cu modifies P25/CeO2 heterojunctions prepared by photodeposition (P25 is commercial TiO2). The local surface plasmon resonance (LSPR) effect caused by Cu nanoparticles broadens the spectral response range and generates significant photothermal effects. After 90 s of irradiation, the temperature of 9.5 %Cu-P25/CeO2 increases to 148.1 °C. The photocatalytic hydrogen evolution rate (HER) of 9.5 %Cu-P25/CeO2 under visible light (λ = 400 nm) reaches 1538.2 μmol h−1 g−1, which is 158.6 times, 17.7 times, and 2.5 times higher than that of Cerium dioxide (CeO2), P25, and P25/CeO2, respectively. This catalyst has stronger light absorption, easier carrier transfer, and separation. This study guides the construction of efficient hydrogen evolution photocatalysts.

Charge Transfer Kinetics and Thermodynamics Control the Energy Conversion Efficiency of a Gallium Phosphide Solar Hydrogen Photocathode.

P-type gallium phosphide (GaP) photocathodes for hydrogen evolution from water have a theoretical energy conversion efficiency of 12% based on the 2.4 eV optical band gap of the material. The performance of actual GaP photocathodes is much lower, for reasons not entirely clear. Here we use vibrating Kelvin probe surface photovoltage (VKP-SPV), open circuit potential (OCP) measurements, and photoelectrochemical (PEC) experiments to evaluate the kinetic and thermodynamic factors that control energy conversion with GaP photocathodes for the hydrogen evolution reaction (HER). We find that the open circuit photovoltage of the bare GaP-H2O junction is limited by recombination at surface states and that an CdS overlayer increases both photovoltage and photocurrent due to formation of a n-p-junction. An optimized GaP/CdS/Pt photocathode drives hydrogen evolution with a quantum efficiency of 62% at 400 nm and 0.0 V RHE and an open circuit photovoltage of 0.43 V at 250 mW cm-2. The Pt cocatalyst increases the photocurrent due to improve HER kinetics but reduces the photovoltage by promoting recombination. Added hydrogen or oxygen gas raise or lower the photovoltage by modifying the electrostatic barrier (band bending) in GaP. This shows that the GaP/CdS junction is not "buried" but behaves like a Schottky junction whose charge separating properties are controlled by the electrochemical potential of the electrolyte. The dynamic junction properties need to be considered in the design of optimized hydrogen evolution photoelectrodes and photocatalysts. Additionally, the work reveals that PEC or OCP measurements tend to underestimate the photovoltage because they do not account for changes in the electrochemical potential at the electrode-liquid contact. In contrast, the VKP-SPV method provides the open circuit photovoltage value directly. By combining the photovoltage data with OCP data, the minority carrier electrochemical potential at the electrode-liquid contact can be measured in a contactless way. This provides an improved understanding of illuminated photoelectrodes for the production of solar fuels.

Improvement of the hydrogen evolution reaction and photocatalyst activity of ZiF-8 coated with RGO

The need for sustainable energy production is critical because of the considerable impact on the environment associated with the use of fossil fuels. In this study, we examine the physicochemical properties, photocatalytic performance, and electrochemical hydrogen evaluation of ZiF-8 coated with RGO, which were prepared using the ultrasonication method. All samples were examined with x-ray diffraction and exhibited a cubic phase. With an increase in RGO concentrations, the direct optical bandgap transition experienced a decline from 5.6 to 3.62 eV. As the concentration of RGO increased, a higher quantity of RGO was added resulting in the formation of a single layer of amorphous RGO on the surface. This layer of amorphous RGO played a key role in enhancing the electronic conductivity of the samples. The RGO coating effect on the photocatalytic performance since the efficiency of dye removal increased from 67% to 99% in 120 minutes. ZiF-8 combined with 8% RGO (ZiF-8@8%RGO) has a noticeably smaller arc radius compared to pure ZIF-8 and ZIF-8 with 4% RGO. The pure ZiF-8 is a typical n-type semiconductor. The ZiF-8@8%RGO demonstrated the highest rate of hydrogen evolution. These results suggest the feasibility of using ZiF-8@8%RGO for photoelectrochemical hydrogen generation.

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.

High-efficiency photocatalytic H2-evolution in water/seawater over a novel noble metal free Ni3C/Mn0.5Cd0.5S Schottky junction

Solar-powered seawater production of clean hydrogen fuel is highly prospective. In this work, Ni3C/Mn0.5Cd0.5S (NCMCS) Schottky junctions with excellent visible-light correspondence and photogenerated carrier separation properties are constructed using electrostatic attraction. The material achieves a hydrogen evolution rate of 6472.9 μmol h−1 g−1 in simulated seawater, which is 11 times higher than that of a single Mn0.5Cd0.5S (MCS). More attractively, the composite exhibits excellent hydrogen evolution rates in natural river water, groundwater and tap water, with significantly enhanced practical applicability. The underlying hydrogen evolution mechanism was extrapolated from a combination of experimental and theoretical calculations. The present work provides a low-cost and efficient hydrogen evolution photocatalyst for practical application, which can help promote the efficient conversion of solar-hydrogen energy.

Easy Scalable Solid-State Synthesis of Highly Efficient Synergetic 2D/1D Micro/Nanostructured g-C3N4/MeS (Me=Cd, Mo) Photocatalysts for Organic Dye Degradation and Hydrogen Evolution

The global reserves of oil, gas, and coal are acknowledged finite, and their consumption rates are increasing each year [1]. Following Fujishima’s groundbreaking discovery of photocatalytic water splitting using TiO2 electrodes in 1972 [2], photocatalysis technology gained recognition as a promising approach for renewable energy and environmental conservation [3]. Since that pivotal moment, significant advancements have been made in developing preparation methods for highly efficient photocatalysts, predominantly centered on semiconductors like metal oxides and sulfides [4].In this study, we introduce effective synergistic photocatalysts, that utilize g-C3N4 and MeS (Me=Cd, Mo) semiconductors featuring a 2D/1D micro/nanostructure. Photocatalysts were successfully produced through solid-state method using planetary ball mill, where reaction of MeS formation occurs on the surface of g-C3N4. A comprehensive analysis of the binding energy of electrons of semiconductors was conducted to understand its impact on the photocatalytic activity of the prepared g-C3N4/MeS. The fabricated materials were used in the photodegradation of organic dyes and demonstrated remarkable efficacy. Regarding photocatalytic hydrogen evolution, the g-C3N4/CdS in conjunction with Pt co-catalyst, achieved a hydrogen evolution rate of up to 2254.54 μmol*h⁻¹ *g⁻¹, accompanied by apparent quantum efficiency of 2.0%. Acknowledgments This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. АР13068426).

Ternary conjugated microporous polymer boosted photocatalytic hydrogen evolution via dual heterocyclic strategy

Heterocyclic organic semiconductors have attracted significant attention as photocatalysts for hydrogen evolution due to excellent absorbency and abundant active sites. Herein, we developed a dual heterocyclic (O/S) conjugated microporous polymer Py-Th-Fu, consisting of both the furan and thiophene heterocycles, for photocatalytic H2 evolution. Compared with the furan O-heterocycle Py-Fu and thiophene S-heterocycle Py-Th, the Py-Th-Fu with the dual heterocyclic structure is more outstanding in regulating the optoelectronic properties, morphological properties, electric charge shift kinetics, and photocatalytic H2 evolution activity. Computational analysis also elucidates the smallest hydrogen adsorption free energy of Py-Th-Fu, which suggests it is the most advantageous for hydrogen mass transfer in this dual heterocycle polymer. As a result, the synergistic combination of two different heteroatom catalytic sites enables the dual heterocycle Py-Th-Fu to afford enhanced catalytic activity with an optimal rate of 23.28 mmol g−1 h−1, which is nearly equal to 5.06 and 1.58 times that of the corresponding O- and S-containing single heterocycles Py-Fu and Py-Th under visible lighting (λ > 420 nm). Our study demonstrates that the dual heterocyclic strategy using ternary copolymerization to tune the optoelectronic properties may open the horizon for fabricating high-performance photocatalytic water splitting via sunlight-driven hydrogen evolution.

Photothermal-enhanced magnetic Cd0.9Zn0.1S/CoB Schottky heterojunction toward photocatalytic hydrogen evolution

The construction of heterojunctions effectively suppresses the undesired recombination of photogenerated charge carriers. This work presents the rational design and preparation of a novel Cd0.9Zn0.1S/CoB (CZS/CoB) Schottky heterojunction tailored for photothermal-assisted photocatalytic hydrogen evolution with the aid of the predictions of density functional theory (DFT). Under visible light irradiation, the hydrogen evolution rate of CZS/CoB reaches 2.56 times that of pure CZS, due to the formed Schottky heterojunction and photothermal properties, effectively inhibiting electron-hole recombination and boosting the photocatalytic reaction. Notably, with the help of the excellent magnetic properties of CoB, the as-synthesized CZS/CoB exhibits excellent magnetic separation property, which is crucial for practical application. The charge transfer pathways in the Schottky heterojunction were confirmed by experimental results and verified by DFT calculation results. This study presents a feasible strategy for the design and preparation of magnetic recyclable Schottky Heterojunction photocatalyst for photocatalytic hydrogen evolution.

Photocatalytic hydrogen evolution on tubular shape cellulose acetate/crystalline nanocellulose/polyvinyl alcohol membranes with embedded nanocrystalline catalysts

In this work, we design an efficient and cost-effective porous membrane composed by polymeric blend that supports different photocatalytic materials. The thin (300 μm) porous photocatalytic membrane has a tubular shape and was flexible for easy handle in the reactor. The membrane is composed of a polymeric blend based on cellulose acetate, crystalline nanocellulose and polyvinyl alcohol, obtained by the phase inversion method, using cold water as non-solvent. Bismuthates (KBiO3, NaBiO3) and aluminates (ZnAl2O4 and Cu0·9Zn0·1Al2O4) powders were synthesized by diverse methodologies and were embedded into polymeric matrix. The hydrogen evolution performance of photocatalyst powders and photocatalytic composite membranes, under UV light irradiation during 180 min, were compared. The best result of hydrogen evolution was obtained by Cu0·9Zn0·1Al2O4 powders reaching 117.74 μmolg−1h−1 and the M−CuZn membrane reaching 90.07 μmolg−1h−1. The obtained results show the high potential of these polymeric membranes as a green alternative support for photocatalysts for hydrogen evolution.

PdS-ZnS-Doped Electrospun Polymer Nanofibers as Effective Photocatalyst for Hydrogen Evolution

Poly(vinyl acetate) nanofibers doped with PdS-ZnS nanoparticles (PdS-ZnS/PVAc nanofibers) were fabricated via an electrospinning technique. PdS-ZnS nanoparticles were in situ synthesized by adding (NH4)2S solution to poly(vinyl acetate)/zinc acetate/palladium acetate solution. Electrospinning of the formed colloidal solution led to the formation of poly(vinyl acetate) nanofibers containing uniformly distributed PdS-ZnS nanoparticles. The prepared samples were characterized by field emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. In photocatalytic activity investigation, the PdS-ZnS/PVAc nanofibers showed remarkably enhanced performance towards water photosplitting under solar irradiation compared to the ZnS/PVAc nanofibers. This enhanced performance is attributed to the synergistic effects of heterostructured PdS-ZnS nanoparticles, which can improve photogenerated charge migration and solar light absorption.

Cerium (III)‐MOF as a photocatalyst for hydrogen evolution from water splitting

Cerium (III)‐MOF as a photocatalyst for hydrogen evolution from water splitting