Ultrathin Niobate Nanosheet Assembly with Au NPs and CdS QDs as a Highly Efficient Photocatalyst

Niobate nanosheets have aroused widespread interest in recent years for their prospects in catalysis. The exploration of 2D niobate catalysis with stable and efficient properties is still the focus in chemistry and materials science. Herein, the successful fabrication of 2D CdS/Au/HNb₃O₈ catalyst is demonstrated which revealed efficient photocatalytic properties in H₂ evolution, oxidative self-coupling of amines to imines, and degradation of dyes. Especially the assembled architecture can give a rate of 5.85 mmol ⋅ g⁻¹ ⋅ h⁻¹ of photocatalytic H₂ evolution, an ∼254-fold enhancement, compared with bare HNb₃O₈ nanosheets under identical conditions. In accordance with density functional theory (DFT) and X-ray adsorption fine structure (XAFS) analyses, the vast improvements are benefited from efficient migration and separation of charge carriers. Besides, the surface plasma resonance (SPR) effect of Au NPs enhances the light harvesting capacity and boosts the generation of hot electrons, efficiently improving the visible-light absorption.     

An Efficient,Visible‐Light‐Driven,Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/Zn_xCd_1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn_0.5Cd_0.5S exhibits an optimal HER rate of 16.78 mmol g⁻¹ h⁻¹ and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.     

The Keto-Switched Photocatalysis of Reconstructed Covalent Organic Frameworks for Efficient Hydrogen Evolution

The keto-switched photocatalysis of covalent organic frameworks (COFs) for efficient H₂ evolution was reported for the first time by engineering, at a molecular level, the local structure and component of the skeletal building blocks. A series of imine-linked BT-COFs were synthesized by the Schiff-base reaction of 1, 3, 5-benzenetrialdehyde with diamines to demonstrate the structural reconstruction of enol to keto configurations by alkaline catalysis. The keto groups of the skeletal building blocks served as active injectors, where hot π-electrons were provided to Pt nanoparticles (NPs) across a polyvinylpyrrolidone (PVP) insulting layer. The characterization results, together with density functional theory calculations, indicated clearly that the formation of keto-injectors not only made the conduction band level more negative, but also led to an inhomogeneous charge distribution in the donor-acceptor molecular building blocks to form a strong intramolecular built-in electric field. As a result, visible-light photocatalysis of TP-COFs-1 with one keto group in the skeletal building blocks was successfully enabled and achieved an impressive H₂ evolution rate as high as 0.96 mmol g⁻¹ h⁻¹. Also, the photocatalytic H₂ evolution rates of the reconstructed BT-COFs-2 and -3 with two and three keto-injectors were significantly enhanced by alkaline post-treatment.     

Enhancing Built-in Electric Fields for Efficient Photocatalytic Hydrogen Evolution by Encapsulating C60 Fullerene into Zirconium-Based Metal-Organic Frameworks

High-efficiency photocatalysts based on metal-organic frameworks (MOFs) are often limited by poor charge separation and slow charge-transfer kinetics. Herein, a novel MOF photocatalyst is successfully constructed by encapsulating C₆₀ into a nano-sized zirconium-based MOF, NU-901. By virtue of host-guest interactions and uneven charge distribution, a substantial electrostatic potential difference is set-up in C₆₀@NU-901. The direct consequence is a robust built-in electric field, which tends to be 10.7 times higher in C₆₀@NU-901 than that found in NU-901. In the catalyst, photogenerated charge carriers are efficiently separated and transported to the surface. For example, photocatalytic hydrogen evolution reaches 22.3 mmol g⁻¹ h⁻¹ for C₆₀@NU-901, which is among the highest values for MOFs. Our concept of enhancing charge separation by harnessing host-guest interactions constitutes a promising strategy to design photocatalysts for efficient solar-to-chemical energy conversion.     

Designed Construction of SrTiO3/SrSO4/Pt Heterojunctions with Boosted Photocatalytic H2 Evolution Activity

Efficient separation of photogenerated electron–hole pairs is a crucial factor for high-performance photocatalysts. Effective electron–hole separation and migration could be achieved by heterojunctions with suitable band structures. Herein, a porous SrTiO₃/SrSO₄ heterojunction is prepared by a sol-gel method at room temperature followed by an annealing process. XRD characterization suggests high crystallinity of the heterostructure. A well-defined interface between the two phases is confirmed by high-resolution (HR)TEM. The photocatalytic H₂ evolution productivity of the SrTiO₃/SrSO₄ heterojunction with Pt as co-catalyst reaches 396.82 μmol g⁻¹ h⁻¹, which is 16 times higher than that of SrTiO₃/Pt. The boosted photocatalytic activity of SrTiO₃/SrSO₄/Pt can be ascribed to the presence of SrSO₄, which promotes the transfer and migration of photogenerated carriers by forming the heterojunction and porous structure, which provides a large amount of active sites. This novel porous heterostructure brings new ideas for the development of high-efficiency photocatalysts for H₂ release.     

Significant Acceleration of Photocatalytic CO2 Reduction at the Gas-Liquid Interface of Microdroplets**

Solar-driven CO₂ reduction reaction (CO₂RR) is largely constrained by the sluggish mass transfer and fast combination of photogenerated charge carriers. Herein, we find that the photocatalytic CO₂RR efficiency at the abundant gas-liquid interface provided by microdroplets is two orders of magnitude higher than that of the corresponding bulk phase reaction. Even in the absence of sacrificial agents, the production rates of HCOOH over WO₃ ⋅ 0.33H₂O mediated by microdroplets reaches 2536 μmol h⁻¹ g⁻¹ (vs. 13 μmol h⁻¹ g⁻¹ in bulk phase), which is significantly superior to the previously reported photocatalytic CO₂RR in bulk phase reaction condition. Beyond the efficient delivery of CO₂ to photocatalyst surfaces within microdroplets, we reveal that the strong electric field at the gas-liquid interface of microdroplets essentially promotes the separation of photogenerated electron-hole pairs. This study provides a deep understanding of ultrafast reaction kinetics promoted by the gas-liquid interface of microdroplets and a novel way of addressing the low efficiency of photocatalytic CO₂ reduction to fuel.     

Construction of CoS2/Zn0.5Cd0.5S S-Scheme Heterojunction for Enhancing H2 Evolution Activity Under Visible Light

In the field of photocatalysis, building a heterojunction is an effective way to promote electron transfer and enhance the reducibility of electrons. Herein, the S-scheme heterojunction photocatalyst (CoS₂/Zn_0.5Cd_0.5S) of CoS₂ nanospheres modified Zn_0.5Cd_0.5S solid solution was synthesized and studied. The H₂ evolution rate of the composite catalyst reached 25.15 mmol g⁻¹ h⁻¹, which was 3.26 times that of single Zn_0.5Cd_0.5S, whereas pure CoS₂ showed almost no hydrogen production activity. Moreover, CoS₂/Zn_0.5Cd_0.5S had excellent stability and the hydrogen production rate after six cycles of experiments only dropped by 6.19 %. In addition, photoluminescence spectroscopy and photoelectrochemical experiments had effectively proved that the photogenerated carrier transfer rate of CoS₂/Zn_0.5Cd_0.5S was better than CoS₂ or Zn_0.5Cd_0.5S single catalyst. In this study, the synthesized CoS₂ and Zn_0.5Cd_0.5S were both n-type semiconductors. After close contact, they followed an S-scheme heterojunction electron transfer mechanism, which not only promoted the separation of their respective holes and electrons, but also retained a stronger reduction potential, thus promoting the reduction of H⁺ protons in photocatalytic experiments. In short, this work provided a new basis for the construction of S-scheme heterojunction in addition to being used for photocatalytic hydrogen production.     

One-pot synthesis of SrTiO3-SrCO3 heterojunction with strong interfacial electronic interaction as a novel photocatalyst for water splitting to generate H2

Photocatalytic hydrogen evolution from water splitting is a promising strategy for realizing the vision of carbon neutrality.Herein,a novel Sr Ti O₃-Sr CO₃n-n heterojunction was used for the first time for water splitting to generate H₂.The heterojunction was synthesized by a soft chemical one-pot hydrothermal method.The Sr Ti O₃-Sr CO₃loading with 3 wt%Pt shows the maximum photocatalytic H₂evolution rate of3.62 mmol h^-1     

Disclosing Support-Size-Dependent Effect on Ambient Light-Driven Photothermal CO2 Hydrogenation over Nickel/Titanium Dioxide

The size of support in heterogeneous catalysts can strongly affect the catalytic property but is rarely explored in light-driven catalysis. Herein, we demonstrate the size of TiO₂ support governs the selectivity in photothermal CO₂ hydrogenation by tuning the metal-support interactions (MSI). Small-size TiO₂ loading nickel (Ni/TiO₂-25) with enhanced MSI promotes photo-induced electrons of TiO₂ migrating to Ni nanoparticles, thus favoring the H₂ cleavage and accelerating the CH₄ formation (227.7 mmol g⁻¹ h⁻¹) under xenon light-induced temperature of 360 °C. Conversely, Ni/TiO₂-100 with large TiO₂ prefers yielding CO (94.2 mmol g⁻¹ h⁻¹) due to weak MSI, inefficient charge separation, and inadequate supply of activated hydrogen. Under ambient solar irradiation, Ni/TiO₂-25 achieves the optimized CH₄ rate (63.0 mmol g⁻¹ h⁻¹) with selectivity of 99.8 %, while Ni/TiO₂-100 exhibits the CO selectivity of 90.0 % with rate of 30.0 mmol g⁻¹ h⁻¹. This work offers a novel approach to tailoring light-driven catalytic properties by support size effect.     

Strong-Base-Assisted Synthesis of a Crystalline Covalent Triazine Framework with High Hydrophilicity via Benzylamine Monomer for Photocatalytic Water Splitting

Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A route to synthesize crystalline and hydrophilic CTF-HUST-A1 with a benzylamine-functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF-HUST-A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g⁻¹ h⁻¹). Photocatalytic overall water splitting is achieved by depositing dual co-catalysts in CTF-HUST-A1, with H₂ evolution and O₂ evolution rates of 25.4 μmol g⁻¹ h⁻¹ and 12.9 μmol g⁻¹ h⁻¹ in pure water without using sacrificial agent.     

A Robust Photocatalytic Hybrid Material Composed of Metal-Organic Cages and TiO2 for Efficient Visible-Light-Driven Hydrogen Evolution

The design of photochemical molecular devices (PMDs) for photocatalytic H₂ production from water is a meaningful but challenging subject currently. Herein, a Pd₂L₄ type metal-organic cage (denoted as MOC-Q2) is designed as a PMD, which consists of two catalytic centers (Pd²⁺) and four photosensitive ligands (L-2) with four pyridine anchoring groups. Subsequently, the MOC-Q2 is combined with TiO₂ to form TiO₂-MOC-Q2 hybrid materials with different MOC-Q2 contents by a facile sol-gel method, which have micro/mesoporous structures and large surface areas. The optimized TiO₂-MOC-Q2 (6.5 wt%) exhibits high H₂ production activity (7.9 mmol g⁻¹ h⁻¹ within 5 h) and excellent durability, giving a TON value of 23477 or 11739 (based on MOC-Q2 or Pd moles) after recycling for 7 rounds. By contrast, the pure MOC-Q2 only shows an ordinary photocatalytic H₂ production rate (0.84 mmol g⁻¹ h⁻¹ within 5 h) in the homogeneous system. It can be deduced that TiO₂ drives the photocatalysis and simultaneously acts as the structure promoter. This study presents a meaningful and distinctive attempt of a new approach for the design and development of MOC-based heterogeneous photocatalysts.     

An Efficient and Stable MoS2/Zn0.5Cd0.5S Nanocatalyst for Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen evolution by water splitting is highly important for the application of hydrogen energy and the replacement of fossil fuel by solar energy, which needs the development of efficient catalysts with long-term catalytic stability under light irradiation in aqueous solution. Herein, Zn_0.5Cd_0.5S solid solution was synthesized by a metal–organic framework-templated strategy and then loaded with MoS₂ by a hydrothermal method to fabricate a MoS₂/Zn_0.5Cd_0.5S heterojunction for photocatalytic hydrogen evolution. The composition of MoS₂/Zn_0.5Cd_0.5S was fine-tuned to obtain the optimized 5 wt % MoS₂/Zn_0.5Cd_0.5S heterojunction, which showed a superior hydrogen evolution rate of 23.80 mmol h⁻¹ g⁻¹ and steady photocatalytic stability over 25 h. The photocatalytic performance is due to the appropriate composition and the formation of an intimate interface between MoS₂ and Zn_0.5Cd_0.5S, which endows the photocatalyst with high light-harvesting ability and effective separation of photogenerated carriers.     

An Efficient,Visible‐Light‐Driven,Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/Zn_xCd_1?xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn_0.5Cd_0.5S exhibits an optimal HER rate of 16.78 mmol g^?1 h^?1 and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.     

Isotypic heterojunction based on Fe-doped and terephthalaldehyde-modified carbon nitride for improving photocatalytic degradation with simultaneous hydrogen production

To achieve an efficient photocatalytic for clean energy production and environmental remediation, the highly active Fe-doped and terephthalaldehyde-modified carbon nitride (Fe-CN/NTE) isotypic heterojunction photocatalyst is constructed via a simple annealing method for degradation of organic pollutants with simultaneous resource recovery. The Fe-CN/NTE catalyst exhibits a 93% removal rate of p-nitrophenol (4-NP) and a 1.72 mmol/g H₂ evolution rate in 2 h simultaneously under visible light irradiation, which are higher than those of pristine CN, Fe-CN, and NTE, respectively. Photoelectrochemical tests show that the excellent photocatalytic performance of Fe-CN/NTE comes from the improved migration, transportation, and separation of photoinduced charge carriers and expanded light-harvesting range. Moreover, hydroxyl radical (OH), electron (e⁻), and hole (h⁺) are the main active species and the rational mechanism of 4-NP photodegradation was proposed based on scavenger measurements and liquid chromatography-mass spectrometry (LC–MS), respectively. Isotypic heterojunction Fe-CN/NTE photocatalyst possesses excellent stability in the H₂ evolution and 4-NP degradation during five-run cycle tests, posing as a promising candidate in practical works for organic pollution and energy challenges.     

Direct Observation of Dynamic Bond Evolution in Single-Atom Pt/C3N4 Catalysts

Single-atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single-atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single-atom Pt/C₃N₄ catalyst in photocatalytic water splitting by synchronous illumination X-ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt−N bond cleavage to form a Pt⁰ species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum-decorated C₃N₄ catalyst. As expected, H₂ production activity (14.7 mmol h⁻¹ g⁻¹) was enhanced significantly with the single-atom Pt/C₃N₄ catalyst as compared to metallic Pt-C₃N₄ (0.74 mmol h⁻¹ g⁻¹).     

Heteroatom-Doped Ag25 Nanoclusters Encapsulated in Metal–Organic Frameworks for Photocatalytic Hydrogen Production

Atomically precise metal nanoclusters (NCs) with unique optical properties and abundant catalytic sites are promising in photocatalysis. However, their light-induced instability and the difficulty of utilizing the photogenerated carriers for photocatalysis pose significant challenges. Here, MAg₂₄ (M=Ag, Pd, Pt, and Au) NCs doped with diverse single heteroatoms have been encapsulated in a metal–organic framework (MOF), UiO-66-NH₂, affording MAg₂₄@UiO-66-NH₂. Strikingly, compared with Ag₂₅@UiO-66-NH₂, the MAg₂₄@UiO-66-NH₂ doped with heteroatom exhibits much enhanced activity in photocatalytic hydrogen production, among which AuAg₂₄@UiO-66-NH₂ presents the best activity up to 3.6 mmol g⁻¹ h⁻¹, far superior to all other counterparts. Moreover, they display excellent photocatalytic recyclability and stability. X-ray photoelectron spectroscopy and ultrafast transient absorption spectroscopy demonstrate that MAg₂₄ NCs encapsulated into the MOF create a favorable charge transfer pathway, similar to a Z-scheme heterojunction, when exposed to visible light. This promotes charge separation, along with optimized Ag electronic state, which are responsible for the superior activity in photocatalytic hydrogen production.     

In situ integration of efficient photocatalyst Cu1.8S/ZnxCd1-xS heterojunction derived from a metal-organic framework

The development of photocatalysts for hydrogen evolution is a promising alternative to industrial hydrogen evolution; however, generation of high active, recyclable, inexpensive heterojunctions are still challenging. Herein, a novel strategy was developed to synthesize non-noble metal co-catalyst/solid solution heterojunctions using metal-organic frameworks (MOFs) as a precursor template. By adjusting the content of MOFs, a series of Cu_1.8S/Zn_xCd_1-xS heterojunctions were obtained, and the Cu_1.8S(3.7%)/Zn_0.35Cd_0.65S sample exhibits a maximum hydrogen evolution rate of 14.27 mmol h⁻¹ g⁻¹ with an apparent quantum yield of 3.7% at 420 nm under visible-light irradiation. Subsequently, the relationship between the heterojunction and photocatalytic activity were investigated by detailed characterizations and density functional theory (DFT) calculations, which reveal that loading Cu_1.8S can efficiently extend the light absorption, meanwhile, the electrons can efficiently transfer from Zn_0.35Cd_0.65S to Cu_1.8S, thus resulting more photogenerated electrons participating in surface reactions. This result can be valuable inspirations for the exploitation of advanced materials using rationally designed nanostructures for solar energy conversion.     

增强制氢性能的ZnO@ZnS空心微球S型异质结光催化剂

随着近年来工业化进程的加速,能源消耗急剧增加,同时伴随着环境的恶化,开发可再生能源的需求日益迫切.氢能因具有高能量密度、零碳排放和可循环利用性而被认为是化石燃料最理想的替代者之一.当下几种制氢技术(如水电解法、丙烷脱氢法和石脑油热解法等)通常需要高温或高功耗,因此其大规模应用受到限制.半导体光催化分解水制氢技术可以将太...     

Engineering a Self-Grown TiO2/Ti-MOF Heterojunction with Selectively Anchored High-Density Pt Single-Atomic Cocatalysts for Efficient Visible-Light-Driven Hydrogen Evolution

A photocatalyst TiO₂/Ti-BPDC-Pt is developed with a self-grown TiO₂/Ti-metal–organic framework (MOF) heterojunction, i.e., TiO₂/Ti-BPDC, and selectively anchored high-density Pt single-atomic cocatalysts on Ti-BPDC for photocatalytic hydrogen evolution. This intimate heterojunction, growing from the surface pyrolytic reconstruction of Ti-BPDC, works in a direct Z-scheme, efficiently separating electrons and holes. Pt is selectively anchored on Ti-BPDC by ligands and is found in the form of single atoms with loading up to 1.8 wt %. The selective location of Pt is the electron-enriched domain of the heterojunction, which further enhances the utilization of the separated electrons. This tailored TiO₂/Ti-BPDC-Pt shows a significantly enhanced activity of 12.4 mmol g⁻¹ h⁻¹ compared to other TiO₂- or MOF-based catalysts. The structure-activity relationship further proves the balance of two simultaneously exposed domains of heterojunctions is critical to fulfilling this kind of catalyst.     

Cd/Pt Precursor Solution for Solar H2 Production and in situ Photochemical Synthesis of Pt Single-atom Decorated CdS Nanoparticles

Despite extensive efforts to develop high-performance H₂ evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H₂ production (154.7 mmol g⁻¹ h⁻¹), removing the need for a pre-synthesized photocatalyst. In addition, we also report simultaneous in situ synthesis of Pt single-atoms anchored CdS nanoparticles (Pt_SA-CdS_IS) during photoirradiation. The highly dispersed in situ incorporation of extensive Pt single atoms on CdS_IS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar-to-hydrogen conversion efficiency of ≈1 % and an apparent quantum yield of over 91 % (365 nm) for H₂ production. Our work not only provides a promising strategy for maximising H₂ production efficiency but also provides a green process for H₂ production and the synthesis of highly photoactive Pt_SA-CdS_IS nanoparticles.