Development Of Photocatalysts Research Articles

Photocatalytic Overall Water Splitting with a Solar-to-Hydrogen Conversion Efficiency Exceeding 2 % through Halide Perovskite.

Photocatalytic water splitting using semiconductors is a promising approach for converting solar energy to clean energy. However, challenges such as sluggish water oxidation kinetics and limited light absorption of photocatalyst cause low solar-to-hydrogen conversion efficiency (STH). Herein, we develop a photocatalytic overall water splitting system using I3 -/I- as the shuttle redox couple to bridge the H2-producing half-reaction with the O2-producing half-reaction. The system uses the halide perovskite of benzylammonium lead iodide (PMA2PbI4, PMA=C6H5CH2NH2) loaded with MoS2 (PMA2PbI4/MoS2) as the H2 evolution photocatalyst, and the RuOx-loaded WO3 (WO3/RuOx) as the O2 evolution photocatalyst, achieving a H2/O2 production in stoichiometric ratio with an excellent STH of 2.07 %. This work provides a detour route for photocatalytic water splitting with the help of I3 -/I- shuttle redox couple in the halide perovskite HI splitting system and enlightens one to integrate and utilize multi catalytic strategies for solar-driven water splitting.

Photocatalytic Overall Water Splitting with a Solar‐to‐Hydrogen Conversion Efficiency Exceeding 2 % through Halide Perovskite

AbstractPhotocatalytic water splitting using semiconductors is a promising approach for converting solar energy to clean energy. However, challenges such as sluggish water oxidation kinetics and limited light absorption of photocatalyst cause low solar‐to‐hydrogen conversion efficiency (STH). Herein, we develop a photocatalytic overall water splitting system using I3−/I− as the shuttle redox couple to bridge the H2‐producing half‐reaction with the O2‐producing half‐reaction. The system uses the halide perovskite of benzylammonium lead iodide (PMA2PbI4, PMA=C6H5CH2NH2) loaded with MoS2 (PMA2PbI4/MoS2) as the H2 evolution photocatalyst, and the RuOx‐loaded WO3 (WO3/RuOx) as the O2 evolution photocatalyst, achieving a H2/O2 production in stoichiometric ratio with an excellent STH of 2.07 %. This work provides a detour route for photocatalytic water splitting with the help of I3−/I− shuttle redox couple in the halide perovskite HI splitting system and enlightens one to integrate and utilize multi catalytic strategies for solar‐driven water splitting.

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.

Enhanced interfacial electric field via sulfur vacancies modified ZnIn2S4-Vs@NiIn2S4 S-scheme photocatalysts for simultaneous H2 evolution and benzyl alcohol oxidation

Designing and developing efficient photocatalysts for H2 evolution and simultaneous oxidation of benzyl alcohol (BA) in aqueous environments provides a cutting-edge strategy for green synthesis. Nevertheless, the photocatalysts suffer from the low photoconversion efficiency because of the sluggish dynamics and repaid recombination of photogenerated charge carriers, which hindering their widespread applications. To address the limitation, a multifunctionnal sulfur vacancies (SVs) modified ZIS-Vs@NIS S-scheme heterojunction with a strong interfacial electric field effect was synthesized to use photocatalytic H2 production and BA oxidation, simultaneously. Experimental analysis supports that the synergistic effect of SVs and S-scheme heterojunction engineering result in a suitable energy band structure alignment and larger Fermi level potential difference. Those factors can realize effective charge transfer and separation, and enhance the photocatalytic performance. As anticipated, ZIS-Vs@NIS exhibited a superior photocatalytic performance with H2 and benzaldehyde (BAD) yields up to 168.1 and 146.1 μmol under the simulated solar-light irradiation for 1.0 h, respectively, which are approximately 13.3 and 11.8 times higher than pristine ZIS. Moreover, the photocatalytic H2 evolution coupled with BA oxidative dehydrogenation mechanism via S-scheme heterojunction over ZIS-Vs@NIS is also demonstrated in detail.

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.

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

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.

All‐in‐One: Plasmonic Janus Heterostructures for Efficient Cooperative Photoredox Catalysis

AbstractJanus heterostructures consisting of multiple jointed components with distinct properties have gained growing interest in the photoredox catalytic field. Herein, we have developed a facile low‐temperature method to gain anisotropic one‐dimensional Au‐tipped CdS (Au−CdS) nanorods (NRs), followed by assembling Ru molecular co‐catalyst (RuN5) onto the surface of the NRs. The CdS NRs decorated with plasmonic Au nanoparticles (NPs) and RuN5 complex harness the virtues of metal‐semiconductor and inorganic‐organic interface, giving directional charge transfer channels, spatially separated reaction sites, and enhanced local electric field distribution. As a result, the Au−CdS−RuN5 can act as an efficient dual‐function photocatalyst for simultaneous H2 evolution and valorization of biomass‐derived alcohols. Benefiting from the interfacial charge decoupling and selective chemical bond activation, the optimal all‐in‐one Au−CdS−RuN5 heterostructure shows greatly enhanced photoactivity and selectivity as compared to bare CdS NRs, along with a remarkable apparent quantum yield of 40.2 % at 400 nm. The structural evolution and working mechanism of the heterostructures are systematically analyzed based on experimental and computational results.

Composition-Regulated Photocatalytic Activity of ZnIn2S4@CdS Hybrids for Efficient Dye Degradation and H2O2 Evolution.

Heterostructures of visible light-absorbing semiconductors were prepared through the growth of ZnIn2S4 crystallites in the presence of CdS nanostructures. A variety of hybrid compositions was synthesized. Both reference samples and heterostructured materials were characterized in detail, regarding their morphology, crystalline character, chemical speciation, as well as vibrational properties. The abovementioned physicochemical characterization suggested the absence of doping phenomena, such as the integration of either zinc or indium ions into the CdS lattice. At specific compositions, the growth of the amorphous ZnIn2S4 component was observed through both XRD and Raman analysis. The development of heterojunctions was found to be composition-dependent, as indicated by the simultaneous recording of the Raman profiles of both semiconductors. The optical band gaps of the hybrids range at values between the corresponding band gaps of reference semiconductors. The photocatalytic activity was assessed in both organic dye degradation and hydrogen peroxide evolution. It was observed that the hybrids demonstrating efficient photocatalytic activity in dye degradation were rather poor photocatalysts for hydrogen peroxide evolution. Specifically, the hybrids enriched in the CdS component were shown to act efficiently for hydrogen peroxide evolution, whereas ZnIn2S4-enriched hybrids demonstrated high potential to photodegrade an azo-type organic dye. Furthermore, scavenging experiments suggested the involvement of singlet oxygen in the mechanistic path for dye degradation.