Photocatalytic hydrogen evolution from glycerol-water mixture under visible light over zinc indium sulfide (ZnIn(2)S(4)) nanosheets grown on bismuth oxychloride (BiOCl) microplates

Exploring the photothermal effect in the photocatalytic water splitting over Type II ZnIn2S4/CoFe2S4 composites

Hydrogen is increasingly acknowledged as a viable alternative to traditional fossil fuels. However, the photothermal properties of CoFe2S4, a photocatalyst displaying metal-like behavior, have not been adequately explored in the context of photocatalytic H2 generation. To improve photocatalytic hydrogen evolution, it is crucial to understand how to expedite the transfer of photogenerated electrons and the dissociation of H-OH bonds for enhanced hydrogen ion release. Herein, a type-II heterostructure was constructed between CoFe2S4 nanosheets and ZnIn2S4 nanoparticles, a non-precious metal photocatalyst, which effectively separates photogenerated carriers and holes. More importantly, the photothermal effect and localized surface plasmon resonance (LSPR) effects induced by CoFe2S4 improved the sluggish kinetics of water dissociation. The CoFe2S4/ZnIn2S4-5 photocatalyst achieved H2 evolution rate of 6.84 mmol·g-1·h-1, and an apparent quantum efficiency of 15.6 % at 400 nm, significantly enhancing the efficiency of photocatalytic splitting for hydrogen production. This work advances the application of metal CoFe2S4 in solar-to-fuel conversion and offers valuable insights for designing semiconductor-based photothermally assisted photocatalytic systems.

Surface Plasmon Resonance-Mediated Photocatalytic H2 Generation

The limited yield of H2 production has posed a significant challenge in contemporary research. To address this issue, researchers have turned to the application of surface plasmon resonance (SPR) materials in photocatalytic H2 generation. SPR, arising from collective electron oscillations, enhances light absorption and facilitates efficient separation and transfer of electron-hole pairs in semiconductor systems, thereby boosting photocatalytic H2 production efficiency. However, existing reviews predominantly focus on SPR noble metals, neglecting non-noble metals and SPR semiconductors. In this review, we begin by elucidating five different SPR mechanisms, covering hot electron injection, electric field enhancement, light scattering, plasmon-induced resonant energy transfer, and photo-thermionic effect, by which SPR enhances photocatalytic activity. Subsequently, a comprehensive overview follows, detailing the application of SPR materials-metals, non-noble metals, and SPR semiconductors-in photocatalytic H2 production. Additionally, a personal perspective is offered on developing highly efficient SPR-based photocatalysis systems for solar-to-H2 conversion in the future. This review aims to guide the development of next-gen SPR-based materials for advancing solar-to-fuel conversion.

Facile synthesis of Bi2ZnB2O7-MoS2nanocomposite for photodetector and photocatalytic Rhodamine B dye degradation application

In this research, the visible light active performance of Bi2ZnB2O7(BBZO) was significantly enhanced through the formation of a composite with few layer MoS2. The resultant MoS2@BBZO catalyst was employed in both photocatalysis and photodetector applications. Comprehensive structural and morphological analyses of the MoS2@BBZO catalyst were conducted using x-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy. The estimated band gaps of BBZO and the composite were found to be 2.8 eV and 1.74 eV, respectively. Rhodamine B degradation studies demonstrated that the catalyst achieved 75% degradation within 30 min. Additionally, the photodetector application was investigated, revealing rapid photo-switching capabilities and an increased photocurrent.

Solar-Driven Biomass Reforming for Hydrogen Generation: Principles, Advances, and Challenges

Hydrogen (H2) has emerged as a clean and versatile energy carrier to power a carbon-neutral economy for the post-fossil era. Hydrogen generation from low-cost and renewable biomass by virtually inexhaustible solar energy presents an innovative strategy to process organic solid waste, combat the energy crisis, and achieve carbon neutrality. Herein, the progress and breakthroughs in solar-powered H2 production from biomass are reviewed. The basic principles of solar-driven H2 generation from biomass are first introduced for a better understanding of the reaction mechanism. Next, the merits and shortcomings of various semiconductors and cocatalysts are summarized, and the strategies for addressing the related issues are also elaborated. Then, various bio-based feedstocks for solar-driven H2 production are reviewed with an emphasis on the effect of photocatalysts and catalytic systems on performance. Of note, the concurrent generation of value-added chemicals from biomass reforming is emphasized as well. Meanwhile, the emerging photo-thermal coupling strategy that shows a grand prospect for maximally utilizing the entire solar energy spectrum is also discussed. Further, the direct utilization of hydrogen from biomass as a green reductant for producing value-added chemicals via organic reactions is also highlighted. Finally, the challenges and perspectives of photoreforming biomass toward hydrogen are envisioned.

Enhanced piezo-photocatalytic performance in ZnIn2S4/BiFeO3 heterojunction stimulated by solar and mechanical energy for efficient hydrogen evolution

An emerging approach that employs both light and vibration energy on binary photo-/piezoelectric semiconductor materials for efficient hydrogen (H2) evolution has garnered considerable attention. ZnIn2S4 (ZIS) is recognized as a promising visible-light-activated photocatalyst. However, its effectiveness is constraint by the slow separation dynamics of photoexcited carriers. Density functional theory (DFT) predictions have shown that the integration of piezoelectric BiFeO3 (BFO) is conducive to the reduction of the H2 adsorption free energy (ΔGH*) for the photocatalytic H2 evolution reaction, thereby enhancing the reaction kinetics. Informed by theoretical predictions, piezoelectric BFO polyhedron particles were successfully synthesized and incorporated with ZIS nanoflowers to create a ZIS/BFO heterojunction using an ultrasonic-assisted calcination method. When subjected to simultaneous ultrasonic treatment and visible-light irradiation, the optimal ZIS/BFO piezoelectric enhanced (piezo-enhanced) heterojunction exhibited a piezoelectric photocatalytic (piezo-photocatalytic) H2 evolution rate approximately 6.6 times higher than that of pristine ZIS and about 3.0 times greater than the rate achieved under light-only conditions. Moreover, based on theoretical predictions and experimental results, a plausible mechanism and charge transfer route for the enhancement of piezo-photocatalytic performance were studied by the subsequent piezoelectric force microscopy (PFM) measurements and DFT calculations. The findings of this study strongly confirm that both the internal electric field of the step-scheme (S-Scheme) heterojunction and the alternating piezoelectric field generated by the vibration of BFO can enhance the transportation and separation of electron-hole pairs. This study presents a concept for the multipath utilization of light and vibrational energy to harness renewable energy from the environment.

Surface and interface engineering of BiOCl nanomaterials and their photocatalytic applications

BiOCl materials have received much attention because of their unique optical and electrical properties. Still, their unsatisfactory catalytic performance has been troubling researchers, limiting the application of BiOCl-based photocatalysts. Therefore, many researchers have studied the adjustment of BiOCl-based materials to enhance photocatalytic efficiency. This review focuses on surface and interface engineering strategies for boosting the photocatalytic performance of BiOCl-based nanomaterials, including forming oxygen vacancy defects, constructing metal/BiOCl, and the fabrication of semiconductor/BiOCl nanocomposites. The photocatalytic applications of the above composites are also concluded in photodegradation of aqueous pollutants, photocatalytic NO removal, photo-induced H2 production, and CO2 reduction. Special emphasis has been given to the modification methods of BiOCl and photocatalytic mechanisms to provide a more detailed understanding for researchers in the fields of energy conversion and materials sciences.

Sulfur defect induced Cd0.3Zn0.7S in-situ anchoring on metal organic framework for enhanced photothermal catalytic CO2 reduction to prepare proportionally adjustable syngas

The rapid recombination of interfacial charges is considered to be the main obstacle limiting the photocatalytic CO2 reduction. Thus, it is a challenge to research an accurate and stable charge transfer control strategy. MIL-53 (Al)-S/Cd0.3Zn0.7S (MAS/CZS-0.3) photocatalysts with chemically bonded interfaces were constructed by in-situ electrostatic assembly of sulfur defect Cd0.3Zn0.7S (CZS-0.3) on the surface of MIL-53 (Al) (MAW), which enhanced interfacial coupling and accelerated electron transfer efficiency. An adjustable proportion of syngas (H2/CO) was prepared by photothermal catalytic CO2 reduction at micro-interface. and the optimal yield of CO (66.10 μmol∙g-1∙h-1) and H2 (71.0 μmol∙g-1∙h-1) was realized by the MAS/CZS-0.3 photocatalyst. The improved activity was due to the photogenerated electrons migrated from CZS-0.3 to the adsorption active sites of MAS, which strengthened the adsorption and activation of CO2 on MAS. The photothermal catalytic CO2 reduction to CO follows the pathway of CO2→*COOH → CO and CO2→*HCO3-→CO. This work provided a reference for the research, characterization, and application of in-situ anchoring of metal organic frameworks in photothermal catalytic CO2 reduction, and provided a green path for the supply of Syngas in industry.

The new method of ZnIn2S4 synthesis on the titania nanotubes substrate with enhanced stability and photoelectrochemical performance

In this work, ZnIn2S4 layers were obtained on fluorine doped tin oxide (FTO) glass and TiO2 nanotubes (TiO2NT) using a hydrothermal process as photoanodes for photoelectrochemical (PEC) water splitting. Then, samples were annealed and the effect of the annealing temperature was investigated. Optimization of the deposition process and annealing of ZnIn2S4 layers made it possible to obtain an FTO-based material generating a photocurrent of 1.2 mA cm-2 at 1.62 V vs. RHE in a neutral medium. In contrast, the highest photocurrent in the neutral electrolyte obtained for the TiO2NT-based photoanode reached 0.5 mA cm-2 at 1.62 V vs. RHE. In addition, the use of a strongly acidic electrolyte allowed the generated photocurrent by the TiO2NT-based photoanode to increase to 3.02 mA cm-2 at 0.31 V vs. RHE. Despite a weaker photoresponse in neutral electrolyte than the optimized FTO-based photoanode, the use of TiO2NT as a substrate allowed for a significant increase in the photoanode's operating time. After 2 h of illumination, the photocurrent response of the TiO2NT-based photoanode was 0.21 mA cm-2, which was 42% of the initial value. In contrast, the FTO-based photoanode after the same time generated a photocurrent of 0.02 mA cm-2 which was only 1% of the initial value. The results indicated that the use of TiO2 nanotubes as a substrate for ZnIn2S4 deposition increases the photoanode's long-term stability in photoelectrochemical water splitting. The proposed charge transfer mechanism suggested that the heterojunction between ZnIn2S4 and TiO2 played an important role in improving the stability of the material by supporting charge separation.

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.

Indium selenide/silver phosphate hollow microsphere S-scheme heterojunctions for photocatalytic hydrogen production with simultaneous degradation of tetracycline

Designing heterojunction photocatalysts with strong interfacial interactions is an effective way to reduce the recombination of photogenerated charge carriers. Here, silver phosphate (Ag₃PO₄) nanoparticles are coupled with hollow flower-like indium selenide (In₂Se₃) microspheres by a facile Ostwald ripening and in-situ growth method, resulting in the construction of In₂Se₃/Ag₃PO₄ hollow microsphere step-scheme (S-scheme) heterojunction with a large contact interface. The flower-like In₂Se₃ with hollow and porous structure provides a large specific surface area and numerous active sites for photocatalytic reactions to take place. The photocatalytic activity was tested by measuring the hydrogen evolution from antibiotic wastewater, and the H₂ evolution rate of In₂Se₃/Ag₃PO₄ reached 4206.4 µmol g^-1h^-1 under visible light, which is approximately 2.8 times greater than that of In₂Se₃. In addition, the amount of tetracycline (TC) degradation when it was used as a sacrificial agent is about 54.4% after 1 h. On the one hand, Se-P chemical bonds act as electron transfer channels in the S-scheme heterojunctions, which can facilitate the migration and separation of photogenerated charge carriers. On the other hand, the S-scheme heterojunctions can retain the useful holes and electrons with higher redox capacities, which is very favorable for the generation of more •OH radicals and the photocatalytic activity is greatly enhanced. This work provides an alternative design approach for photocatalysts toward hydrogen evolution in antibiotic wastewater.

Facile Synthesis of P-Doped ZnIn2S4 with Enhanced Visible-Light-Driven Photocatalytic Hydrogen Production

ZnIn₂S₄ (ZIS) is widely used in the field of photocatalytic hydrogen production due to its unique photoelectric properties. Nonetheless, the photocatalytic performance of ZIS usually faces problems of poor conductivity and rapid recombination of charge carriers. Heteroatom doping is often regarded as one of the effective strategies for improving the catalytic activity of photocatalysts. Herein, phosphorus (P)-doped ZIS was prepared by hydrothermal method, whose photocatalytic hydrogen production performance and energy band structure were fully studied. The band gap of P-doped ZIS is about 2.51 eV, which is slightly smaller than that of pure ZIS. Moreover, due to the upward shift of its energy band, the reduction ability of P-doped ZIS is enhanced, and P-doped ZIS also exhibits stronger catalytic activity than pure ZIS. The optimized P-doped ZIS exhibits a hydrogen production rate of 1566.6 μmol g^-1 h^-1, which is 3.8 times that of the pristine ZIS (411.1 μmol g^-1 h^-1). This work provides a broad platform for the design and synthesis of phosphorus-doped sulfide-based photocatalysts for hydrogen evolution.