Combined Schottky junction and doping effect in CdxZn1-xS@Au/BiVO4 Z-Scheme photocatalyst with boosted carriers charge separation for CO2 reduction by H2O

Improving photocatalytic hydrogen production by switching charge kinetics from type-I to Z-scheme via defective engineering

By providing the spatial separation of the active sites and retaining high oxidative and reducing capacity, the direct Z-scheme heterostructure is considered the most potential structure for yielding photo-electric response. However, challenges still exist in the directional transfer of charge carriers between two semiconductors in direct Z-scheme structures. In this regard, by constructing the Vzn defect and p-n junction, a direct Z-scheme ZnxCd1-xS@ZnS-NiS heterostructure was obtained for the regulated electronic structure, which ensured high-yield hydrogen properties. The Zn vacancy in the partially-coated ZnS shell led to the Vzn energy level, and the addition of NiS led to the p-n structure, which caused a drastic downshift of the band edge potentials in comparison to that of pristine CdS. This variation gave rise to a staggered band edge alignment between ZnxCd1-xS and NiS, resulting in the variation of charge transfer kinetics from type-I to direct Z-scheme. Through careful characterization, it was found that the optimal photocatalytic hydrogen precipitation activity reached 16 683.6 μmol g-1 h-1, which was 70 times that of CdS, and this improvement was considered to form a spatial barrier, providing a clear direction and path for carrier transmission.

Tailored BiVO4 Photoanode Hydrophobic Microenvironment Enables Water Oxidative H2 O2 Accumulation

Direct photoelectrochemical 2-electron water oxidation to renewable H₂ O₂ production on an anode increases the value of solar water splitting. BiVO₄ has a theoretical thermodynamic activity trend toward highly selective water oxidation H₂ O₂ formation, but the challenges of competing 4-electron O₂ evolution and H₂ O₂ decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO₄ -based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O₂ , where coating BiVO₄ with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H₂ O₂ . Also, the hydrophobicity is responsible for the H₂ O₂ production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO₄ surface, it achieves an average Faradaic efficiency (FE) of 81.6% in a wide applied bias region (0.6-2.1 V vs RHE) with the best FE of 85%, which is 4-time higher than BiVO₄ photoanode. The accumulated H₂ O₂ concentration can reach 150 µm at 1.23 V versus RHE under AM 1.5 illumination in 2 h. This concept of modifying the catalyst surface microenvironment via stable polymers provides a new approach to tune the multiple-electrons competitive reactions in aqueous solution.

Recent Progress of Three-dimensionally Ordered Macroporous (3DOM) Materials in Photocatalytic Applications: A Review

In recent years, three-dimensionally ordered macroporous (3DOM) materials have attracted tremendous interest in the field of photocatalysis due to the periodic spatial structure and unique physicochemical properties of 3DOM catalysts. In this review, the fundamentals and principles of 3DOM photocatalysts are briefly introduced, including the overview of 3DOM materials, the photocatalytic principles based on 3DOM materials, and the advantages of 3DOM materials in photocatalysis. The preparation methods of 3DOM materials are also presented. The structure and properties of 3DOM materials and their effects on photocatalytic performance are briefly summarized. More importantly, 3DOM materials, as a supported catalyst, are extensively employed to combine with various common materials, including metal nanoparticles, metal oxides, metal sulfides, and carbon materials, to enhance photocatalytic performance. Finally, the prospects and challenges for the development of 3DOM materials in the field of photocatalysis are presented.

An optimization strategy for photo-Fenton-like catalysts: Based on crystal plane engineering of BiVO4 and electron transfer properties of 0D CQDs

Herein, we report a novel Cu₂(OH)₃ F/CQDs-BiVO₄ composite photo-Fenton-like system, which used BiVO₄ and Cu₂(OH)₃F as electron donor and acceptor, respectively, and achieved efficient electron transfer between them through the electron bridging effect of Carbon quantum dots (CQDs). The material exhibited excellent ciprofloxacin (CIP) removal efficiency in the photo-Fenton-like coupled system. Cu₂(OH)₃ F/CQDs-BiVO₄ had an incredibly fast response rate, eliminating 98.1% of CIP from the solution in just 1 h, according to the reaction kinetics. Exploratory tests proved that the catalyst kept up a sufficient level of activity across a wide pH range of 3-11 and in the presence of various anions. The activity, morphology, and crystal structure of the samples did not appreciably alter after five recycles. Finally, a possible reaction mechanism was also proposed based on the band structure, position and reaction species.

Advanced Photocatalysts for CO2 Conversion by Severe Plastic Deformation (SPD)

Excessive CO₂ emission from fossil fuel usage has resulted in global warming and environmental crises. To solve this problem, the photocatalytic conversion of CO₂ to CO or useful components is a new strategy that has received significant attention. The main challenge in this regard is exploring photocatalysts with high efficiency for CO₂ photoreduction. Severe plastic deformation (SPD) through the high-pressure torsion (HPT) process has been effectively used in recent years to develop novel active catalysts for CO₂ conversion. These active photocatalysts have been designed based on four main strategies: (i) oxygen vacancy and strain engineering, (ii) stabilization of high-pressure phases, (iii) synthesis of defective high-entropy oxides, and (iv) synthesis of low-bandgap high-entropy oxynitrides. These strategies can enhance the photocatalytic efficiency compared with conventional and benchmark photocatalysts by improving CO₂ adsorption, increasing light absorbance, aligning the band structure, narrowing the bandgap, accelerating the charge carrier migration, suppressing the recombination rate of electrons and holes, and providing active sites for photocatalytic reactions. This article reviews recent progress in the application of SPD to develop functional ceramics for photocatalytic CO₂ conversion.

Growth of villi-microstructured bismuth vanadate (Vm-BiVO4) for photocatalytic degradation of crystal violet dye

In this work, villi-microstructured Au-loaded BiVO₄ photocatalysts were successfully synthesized by hydrothermal method. The as-synthesized photocatalysts were characterized by XRD, Raman, UV-Vis-DRS, PL, SEM and EDX techniques. The presence of metallic Au on the surface of Vm-BiVO₄ support boosts the photocatalytic performance to degrade toxic crystal violet dye. The enhanced activities were attributed to the surface plasmon resonance (SPR) of Au which efficiently broadens the visible light response. SPR increases the electron population in Vm-BiVO₄ and forms a Schottky barrier at the interface between Au and Vm-BiVO₄ which enhances the separation efficiency of photoinduced charges. Various factors affecting photocatalytic degradation of crystal violet (CV) were studied to find optimum conditions. In addition, a radical trapping study indicates that ˙O₂ ^- is the main active species in the degradation process of cationic CV dye. All photocatalytic degradation reactions were monitored by UV-Vis spectrophotometry (PerkinElmer/λ-365).

Quantitative Evaluation of Carrier Dynamics in Full-Spectrum Responsive Metallic ZnIn2S4 with Indium Vacancies for Boosting Photocatalytic CO2 Reduction

The influence of defects on quantitative carrier dynamics is still unclear. Therefore, full-spectrum responsive metallic ZnIn₂S₄ (V_In-rich-ZIS) rich in indium vacancies and exhibiting high CO₂ photoreduction efficiency was synthesized for the first time. The influence of the defects on the carrier dynamic parameters was studied quantitatively; the results showed that the minority carrier diffusion length (L_D) is closely related to the catalytic performance. In situ infrared spectroscopy and theoretical calculations revealed that the presence of indium vacancies lowers the energy barrier for CO₂ to CO conversion via the COOH* intermediate. Hence, the high rate of CO evolution reaches 298.0 μmol g^-1 h^-1, a nearly 28-fold enhancement over that with ZnIn₂S₄ (V_In-poor-ZIS), which is not rich in indium vacancies. This work fills the gaps between the catalytic performance of defective photocatalysts and their carrier dynamics and may offer valuable insight for understanding the mechanism of photocatalysis and designing more efficient defective photocatalysts.