Vacancy Engineering in 2D Transition Metal Chalcogenide Photocatalyst: Structure Modulation, Function and Synergy Application

Transition metal chalcogenides (TMCs) are widely used in photocatalytic fields such as hydrogen evolution, nitrogen fixation, and pollutant degradation due to their suitable bandgaps, tunable electronic and optical properties, and strong reducing ability. The unique 2D malleability structure provides a pre-designed platform for customizable structures. The introduction of vacancy engineering makes up for the shortcomings of photocorrosion and limited light response and provides the greatest support for TMCs in terms of kinetics and thermodynamics in photocatalysis. This work reviews the effect of vacancy engineering on photocatalytic performance based on 2D semiconductor TMCs. The characteristics of vacancy introduction strategies are summarized, and the development of photocatalysis of vacancy engineering TMCs materials in energy conversion, degradation, and biological applications is reviewed. The contribution of vacancies in the optical range and charge transfer kinetics is also discussed from the perspective of structure manipulation. Vacancy engineering not only controls and optimizes the structure of the TMCs, but also improves the optical properties, charge transfer, and surface properties. The synergies between TMCs vacancy engineering and atomic doping, other vacancies, and heterojunction composite techniques are discussed in detail, followed by a summary of current trends and potential for expansion.

Unveiling the Role of Sulfur Vacancies in Enhanced Photocatalytic Activity of Hybrids Photocatalysts

Photocatalysis represents a sustainable strategy for addressing energy shortages and global warming. The main challenges in the photocatalytic process include limited light absorption, rapid recombination of photo-induced carriers, and poor surface catalytic activity for reactant molecules. Defect engineering in photocatalysts has been proven to be an efficient approach for improving solar-to-chemical energy conversion. Sulfur vacancies can adjust the electron structure, act as electron reservoirs, and provide abundant adsorption and activate sites, leading to enhanced photocatalytic activity. In this work, we aim to elucidate the role of sulfur vacancies in photocatalytic reactions and provide valuable insights for engineering high-efficiency photocatalysts with abundant sulfur vacancies in the future. First, we delve into the fundamental understanding of photocatalysis. Subsequently, various strategies for fabricating sulfur vacancies in photocatalysts are summarized, along with the corresponding characterization techniques. More importantly, the enhanced photocatalytic mechanism, focusing on three key factors, including electron structure, charge transfer, and the surface catalytic reaction, is discussed in detail. Finally, the future opportunities and challenges in sulfur vacancy engineering for photocatalysis are identified.

MOF-derived sulfur vacancies rich CdS nanoparticles in situ growth on 2D polymer for highly efficient photocatalytic hydrogen generation

For heterojunction photocatalytic materials, the size of nanoparticles and electron-hole separation efficiency have a great influence on the photocatalytic hydrogen production activity. In this work, for the first time, a...

Pt/MnO2 Nanoflowers Anchored to Boron Nitride Aerogels for Highly Efficient Enrichment and Catalytic Oxidation of Formaldehyde at Room Temperature

The catalytic room temperature oxidation of formaldehyde (HCHO) is widely considered as a viable method for the abatement of indoor toxic HCHO pollution. Herein, Pt/MnO₂ nanoflowers anchored to boron nitride aerogels (Pt/MnO₂ -BN) were fabricated for the catalytic room temperature oxidation of HCHO. The three-dimensional Pt/MnO₂ -BN aerogels demonstrated superior catalytic activity as a result of the improved diffusion of the reactant molecules within the porous structure. Furthermore, the porous aerogels displayed excellent HCHO adsorption capacities, which promote a rapid HCHO gas-phase concentration reduction and a subsequent complete oxidation of the adsorbed HCHO. The combined adsorption and oxidation properties of the Pt/MnO₂ -BN aerogels enhance the oxidative removal of HCHO. The optimized Pt/MnO₂ -BN demonstrated excellent catalytic activity toward HCHO (200 ppm) at room temperature, achieving a 96 % formaldehyde conversion after 50 min.

Olivine-type cadmium germanate: a new sensing semiconductor for the detection of formaldehyde at the ppb level

In this study, for the first time, olivine-structured Cd2GeO4 was identified as an excellent formaldehyde sensing material, with a low detection limit of 60 ppb.

Novel Two-Dimensional AgInS2/SnS2/RGO Dual Heterojunctions: High Spatial Charge and Toxicity Evaluation

A single semiconductor employed into photo(electro)catalysis is not sufficient for charge carrier separation. Designing a multiple heterojunction system is a practical method for photo(electro)catalysis. Herein, novel two-dimensional AgInS₂/SnS₂/RGO (AISR) photocatalysts with multiple junctions were prepared by a simple hydrothermal method. The synthesized AISR heterojunctions showed superior photoelectrochemical performance and photocatalytic degradation of norfloxacin, with a high degradation rate reaching 95%. More importantly, the toxicity of photocatalytic products decreased within the reaction process. High spatial separation efficiency of photogenerated electron-hole pairs was evidenced by optical and photoelectrochemical characterizations. Furthermore, a laser flash photolysis technique was carried on investigating the lifetime of the charge carrier of the fabricated dual heterostructures. In addition, sulfur and oxygen vacancies existed in AISR heterojunctions could largely constrain the recombination of electron-hole pairs. Density functional theory calculations were carried out to analyze the mechanism of photoinduced interfacial redox reactions, showing that reduced graphene oxide and AgInS₂ act as electron and hole trappers in the photocatalytic reaction, respectively. Due to the interfacial electric field formed from AISR dual heterojunctions, the effective spatial charge separation and transfer contributed to the boosting photo(electro)catalytic performance.

Photo-catalytic degradation of mixed gaseous HCHO and C6H6 in paper mills: Experimental and theoretical study on the adsorption behavior simulation and catalytic reaction mechanism

VOCs in paper mills have severely exceeded the emission standards and their photo-catalytic degradations should focus on the experimental and theoretical studies. This work used TiO₂ colloid as catalyst to study the photo-catalytic degradations of mixed HCHO and C₆H₆ at five mixing ratios. The adsorption behaviors of pure forms and mixtures on the TiO₂ (101) surface were simulated using density functional theory (DFT), and their catalytic reaction mechanisms were also analyzed. The following results were found: (1) With increasing initial concentration, the enhanced adsorption and easy degradation interpreted the increased degradation rate for pure HCHO, while the counteractions of enhanced adsorption and inhibited catalytic reaction kept the constant degradation rate for pure C₆H₆. (2) For their mixtures, the HCHO degradation was inhibited at high C₆H₆ concentration due to the inhibited adsorption and catalytic reaction of HCHO. The C₆H₆ degradation was slightly weakened at high HCHO concentration and then restored to the normal degradation rate of C₆H₆, which could be attributed to the weakened adsorption of C₆H₆ and the easy degradation of HCHO in the initial stage. The combined experimental, simulation, and theoretical results provides sufficient information to understand the photo-catalytic degradation process for mixed gaseous pollutants in different realistic environments.

Self-molten-polymerization synthesis of highly defected Mn/Sm binary oxides with mesoporous structures for efficient removal of toluene and chlorobenzene

Oxygen vacancies were induced via transition metal doping in MnO_x for the low-temperature and efficient removal of toluene and chlorobenzene.

Rational design of a novel quaternary ZnO@ZnS/Ag@Ag2S nanojunction system for enhanced photocatalytic H2 production

A novel ZnO@ZnS/Ag@Ag₂S quaternary nanojunction photocatalyst has been designed for efficient solar water splitting.