Unique 1D Cd1- x Znx S@O-MoS2 /NiOx Nanohybrids: Highly Efficient Visible-Light-Driven Photocatalytic Hydrogen Evolution via Integrated Structural Regulation

Construction of 2D/1D Cu7S4 nanosheets/Mn0.3Cd0.7S nanorods heterojunction for highly efficient photocatalytic hydrogen evolution

Developing cost-effective cocatalyst-modified photocatalytic systems with boosted carrier separation and rapid surface catalytic reaction is an ideal strategy for effectively converting solar energy into desired fuels. Herein, a series of Cu7S4/Mn0.3Cd0.7S hierarchical heterostructures are designed and fabricated to achieve efficient and robust photocatalytic H2 evolution by coupling one-dimensional (1D) Mn0.3Cd0.7S nanorods with two-dimensional (2D) Cu7S4 nanosheets through a facile sonochemical strategy. Benefiting from dimensionality and cocatalyst effects, the constructed 2D/1D Cu7S4/Mn0.3Cd0.7S heterojunction photocatalyst containing 1.5 wt% Cu7S4 displays excellent photostability and superior photocatalytic H2 evolution rate up to 914.3 μmol h-1, which is 4.43 and 2.22-folds increment relative to bare Mn0.3Cd0.7S and the 3 wt% Pt/Mn0.3Cd0.7S, respectively. The various characterization results reveal that the utilization of semimetallic Cu7S4 nanosheets as the cocatalyst to form a Schottky heterojunction can promote the light-harvesting capability, suppress charge carrier recombination, and provide sufficient reaction sites for hydrogen generation, thereby resulting in the dramatically improved photocatalytic performance. This work clarifies the role of Cu7S4 nanosheets as the robust and cost-effective cocatalyst in the photocatalytic reaction and opens a new horizon for designing other Cu7S4-based cocatalyst/semiconductor Schottky heterostructures for efficient solar-to-fuel conversion.

Porous Host-Guest MOF-Semiconductor Hybrid with Multisites Heterojunctions and Modulable Electronic Band for Selective Photocatalytic CO2 Conversion and H2 Evolution

Optimizing catalysts for competitive photocatalytic reactions demand individually tailored band structure as well as intertwined interactions of light absorption, reaction activity, mass, and charge transport.  Here, a nanoparticulate host-guest structure is rationally designed that can exclusively fulfil and ideally control the aforestated uncompromising requisites for catalytic reactions. The all-inclusive model catalyst consists of porous Co3 O4 host and Znx Cd1- x S guest with controllable physicochemical properties enabled by self-assembled hybrid structure and continuously amenable band gap. The effective porous topology nanoassembly, both at the exterior and the interior pores of a porous metal-organic framework (MOF), maximizes spatially immobilized semiconductor nanoparticles toward high utilization of particulate heterojunctions for vital charge and reactant transfer. In conjunction, the zinc constituent band engineering is found to regulate the light/molecules absorption, band structure, and specific reaction intermediates energy to attain high photocatalytic CO2 reduction selectivity. The optimal catalyst exhibits a H2 -generation rate up to 6720 µmol g-1 h-1 and a CO production rate of 19.3 µmol g-1 h-1 . These findings provide insight into the design of discrete host-guest MOF-semiconductor hybrid system with readily modulated band structures and well-constructed heterojunctions for selective solar-to-chemical conversion.

MoS2-Based Nanocomposites for Photocatalytic Hydrogen Evolution and Carbon Dioxide Reduction

Photocatalysis is a facile and sustainable approach for energy conversion and environmental remediation by generating solar fuels from water splitting. Due to their two-dimensional (2D) layered structure and excellent physicochemical properties, molybdenum disulfide (MoS₂) has been effectively utilized in photocatalytic H₂ evolution reaction (HER) and CO₂ reduction. The photocatalytic efficiency of MoS₂ greatly depends on the active edge sites present in their layered structure. Modifications like reducing the layer numbers, creating defective structures, and adopting different morphologies produce more unsaturated S atoms as active edge sites. Hence, MoS₂ acts as a cocatalyst in nanocomposites/heterojunctions to facilitate the photogenerated electron transfer. This review highlights the role of MoS₂ as a cocatalyst for nanocomposites in H₂ evolution reaction and CO₂ reduction. The H₂ evolution activity has been described comprehensively as binary (with metal oxide, carbonaceous materials, metal sulfides, and metal-organic frameworks) and ternary composites of MoS₂. Photocatalytic CO₂ reduction is a more complex and challenging process that demands an efficient light-responsive semiconductor catalyst to tackle the thermodynamic and kinetic factors. Photocatalytic reduction of CO₂ using MoS₂ is an emerging topic and would be a cost-effective substitute for noble catalysts. Herein, we also exclusively envisioned the possibility of layered MoS₂ and its composites in this area. This review is expected to furnish an understanding of the diverse roles of MoS₂ in solar fuel generation, thus endorsing an interest in utilizing this unique layered structure to create nanostructures for future energy applications.

Fabrication of Z-scheme Cd0.85Zn0.15S/Co9S8dual-functional photocatalyst for effective hydrogen evolution and organic pollutant degradation

A Z-scheme Cd_0.85Zn_0.15S/Co₉S₈(CZS-CS) photocatalyst was reasonably fabricated by a simple solvothermal method for the effective visible-light-driven H₂evolution and organic pollutants degradation. The precise construction of the CZS-CS composites provided an efficient heterogeneous contact interface and abundant reaction sites for the proposed photocatalytic reaction. The homogeneous Co₉S₈nanocrystals were uniformly wrapped on the surface of Cd_0.85Zn_0.15S nanorods, forming an intimate-contact interface, markedly contributed to the light collection and effectively inhibited the charge-carrier recombination. The optimized CZS-CS-15 composites exhibited a special H₂production rate reaching 19.15 mmol·h^-1·g^-1, roughly 1915 and 4.5 times of pure Co₉S₈and Cd_0.85Zn_0.15S samples and 85% of tetracycline (TC) molecule within 15 min was degraded. Furthermore, trapping experiments confirmed that h⁺was the main active species for TC photodegradation. Moreover, the obtained photocatalysts manifested stability without apparent activity declines during the proposed reactions. Finally, the Z-scheme photocatalytic mechanism was verified to illustrate the characteristics of efficient charge transfer and high redox ability. This study provided a rational and learnable strategy for designing dual-functional Z-scheme heterojunction photocatalysts.

Identification of the Stable Pt Single Sites in the Environment of Ions: From Mechanism to Design Principle

For single-atom (SA)-based catalysis, it is urgent to understand the nature and dynamic evolution of SA active sites during the reactions. In this work, an example of Pt SA-Zn_0.5 Cd_0.5 S (Pt SA-ZCS) is found to display interesting phenomena when facing the Brownian collision of ions in aqueous photocatalysis. Via synchrotron radiation, surface techniques, microscopy, and theory calculations, the results show that two kinds of Pt sites exist: Pt_Zn-sub -S₃ (Pt substituting the Zn site) and Pt_ads -S₂ (Pt adsorbing on the surface). In Na₂ S, the S^2- can coordinate with Pt atoms and peel them from the Pt_ads -S₂ sites, but leaves more stable Pt_Zn-sub -S₃ sites, bringing a low but stable catalytic activity (19.40 mmol g^-1 h^-1 ). Meanwhile, in ascorbic acid, the ascorbic acid ions show less complex ability with Pt atoms, but can decrease the migration barrier of Pt_ads -S₂ sites (67.18 down to 35.96 mmol g^-1 h^-1 , 52.03% drop after 6 h). Therefore, the Pt_ads -S₂ sites gradually aggregate into nanoclusters, bringing a high but decayed catalytic activity. Moreover, a Pt SA-ZCS-Sulfur composite is designed mainly covered by Pt_Zn-sub -S₃ sites accordingly (max: 79.09 mmol g^-1 h^-1 , 5% drop after 6 h and QE: 14.0% at 420 nm), showing a beneficial strategy "from mechanism to design principle."

Atomic heterojunction-induced accelerated charge transfer for boosted photocatalytic hydrogen evolution over 1D CdS nanorod/2D ZnIn2S4 nanosheet composites

Design of highly efficient heterojunctions for photocatalytic hydrogen evolution is of significant importance to address the energy shortage and environmental crisis. Nevertheless, the smart design of semiconductor-based heterojunctions at the atomic scale still remains a significant challenge hitherto. Herein, we report novel atomic CdS/ZnIn₂S₄ heterojunctions by in-situ epitaxially growing 2D ZnIn₂S₄ nanosheets onto the surface of 1D defective CdS nanorods. The strong electronic coupling between defective CdS and ZnIn₂S₄ is confirmed by transient photocurrent response measurements, •O₂^- and •OH radicals experiments, and PL results, leading to accelerated interfacial charge separation and transfer. Additionally, the elevated charge transfer and electronic coupling are further confirmed by theoretical calculations. Consequently, CdS/ZnIn₂S₄ hybrids exhibit superior photocatalytic hydrogen generation activity to pristine CdS. Our findings offer a new paradigm for designing atomic 1D/2D heterojunctions for efficient solar-driven energy conversion.

Construction of heterojunctions between ReS2 and twin crystal ZnxCd1−xS for boosting solar hydrogen evolution

Nanoflower-like ReS₂ anchoring on nanotwins Zn_xCd_1−xS greatly boosts photocatalytic hydrogen evolution rate with 31-times higher than pure phase P-ZCS.

Mesoporous CdxZn1-xS with abundant surface defects for efficient photocatalytic hydrogen production

The practical application of photocatalytic water splitting for hydrogen evolution hinges on the development of high-efficient and low-cost photocatalysts. Defects engineering has emerged as a promising strategy to enhance photocatalytic activity effectively. Herein, a facile and versatile co-precipitation method is proposed to fabricate mesoporous Cd-Zn-S solid solutions (E-Cd_xZn_1-xS) with abundant surface defects by the inorganic salts formed in the reaction system as self-template. Compared with Cd-Zn-S solid solutions (W-Cd_0.65Zn_0.35S) prepared by the traditional co-precipitation method, the enhanced specific surface area and abundant surface defects endow E-Cd_0.65Zn_0.35S with more accessible active sites and effective separation of electron-hole pairs for the photocatalytic water splitting reaction. The E-Cd_0.65Zn_0.35S solid solution exhibits hydrogen evolution rate of 5.2 mmol h^-1 g^-1 without loading noble metal as cocatalyst under visible light, which is 1.13 times higher than that of W-Cd_0.65Zn_0.35S sample. The present work provides a simple, low-cost and prospective strategy for the synthesis of defective Cd-Zn-S solid solutions, and it also delivers guidance to design and develop the advanced visible-light photocatalyst in the future.

One-dimensional CdS@Cd0.5Zn0.5S@ZnS-Ni(OH)2 nano-hybrids with epitaxial heterointerfaces and spatially separated photo-redox sites enabling highly-efficient visible-light-driven H2 evolution

Photocatalytic solar-to-fuel conversion has been of great interest in recent years. Nevertheless, the rational structural manipulation of photocatalysts toward an efficient H2 evolution reaction (HER) is still under-developed. In this work, by employing CdS nanowires as the growth substrate, unique one-dimensional (1D) CdS@Cd0.5Zn0.5S@ZnS-Ni(OH)2 heterostructures were first synthesized through the ultrasonic water-bath reaction combined with subsequent hydrothermal and in situ photo-deposition processes. Under the optimized conditions, CS@30CZ0.5S@40ZS-3N with 30 wt% Cd0.5Zn0.5S, 40 wt% ZnS, and 3 wt% Ni(OH)2 achieves a visible-light-driven HER activity as high as 86.79 mmol h-1 g-1 (corresponding to an apparent quantum yield of 22.8% at 420 nm), which is 4 and 119 times higher than that of Pt-decorated CS@30CZ0.5S@40ZS and CdS, respectively. In addition, CdS@Cd0.5Zn0.5S@ZnS-Ni(OH)2 is also endowed with a good stability for H2 production under long-term irradiation. The spatial separation of photo-redox sites and epitaxial heterointerfaces in CdS@Cd0.5Zn0.5S@ZnS-Ni(OH)2 nanowires facilitate the charge transfer and separation effectively, accounting well for their superior photocatalytic capability. The results indicated in this work could benefit the exploitation of high-performance nanostructures for promising photocatalytic applications.

Accelerated charge transfer of Cd0.5Zn0.5S@ZnS core–shell nano-spheres via decoration of Ni2P and g-C3N4 toward efficient visible-light-driven H2 production

Unique Cd_0.5Zn_0.5S@ZnS-Ni₂P/g-C₃N₄ hybrid nano-spheres demonstrate enhanced photostability, improved light-harvesting and facilitated charge separation toward efficient H₂ evolution from visible-light-driven water-splitting.

Designed synthesis of unique ZnS@CdS@Cd0.5Zn0.5S-MoS2 hollow nanospheres for efficient visible-light-driven H2 evolution

Unique ZnS@CdS@Cd_0.5Zn_0.5S-MoS₂ hollow nanospheres with abundant active sites and enhanced light-harvesting and charge separation demonstrate efficient H₂ evolution from visible-light-driven water-splitting.

Two new inorganic–organic hybrid zinc phosphites and their derived ZnO/ZnS heterostructure for efficient photocatalytic hydrogen production

Two novel inorganic–organic hybrid zinc phosphites, namely, [Zn(1,2-bimb)_0.5(HPO₃)]_n (1) and [Zn(1,4-bmimb)_0.5(HPO₃)]_n (2), (1,2-bimb = 1,2-bis(imidazol-1ylmethyl)benzene; 1,4-bmimb = 1,4-bis((2-methyl-1H-imidazol-1yl)methyl)benzene) were synthesized for the first time by hydrothermal reaction. Compound 1 generates a three-dimensional (3D) pillared-layer structure with a 2-nodal 3,4-connected 3,4T15 topology. While compound 2 exhibits a 2D hybrid zinc phosphite sheet with a 3,4-connected 3,4L83 topology network. Utilizing compound 1 and compound 2 as templates and Na₂S as an etching agent, a series of highly efficient ZnO/ZnS photocatalysts were obtained. The optimized 1-160 sample demonstrates the highest evolution rate of 22.6 mmol g⁻¹ h⁻¹, exceeding the rate of commercial ZnS samples by more than 14.5 times. The remarkable photocatalytic activity should be attributed to the unique heterojunction structure which shortens the free path of charge carriers and enhances the charge separation efficiency. This work provides a facile strategy for preparing photocatalysts with efficient photocatalytic hydrogen production derived from inorganic–organic hybrid material.

Though a solvo-thermal synthesis process, two novel inorganic–organic hybrid zinc phosphite were constructed. Using these hybrid zinc phosphite as template, the ZnO/ZnS heterostructures were prepared by a sulfuration method for enhanced photocatalytic performance.