Constructing photocatalysts decorated with atomically dispersed metal species (ADMs) represents a pivotal strategy to maximize atom utilization and tailor active sites for efficient carbon dioxide (CO₂) reduction. However, conventional synthesis strategies, typically relying on tedious wet-chemistry or prolonged thermal calcination, often suffer from slow kinetics that inevitably drive the thermodynamic aggregation of metastable single atoms or nanoclusters into less active nanoparticles. Herein, we bypass these limitations by developing a facile flash Joule heating (FJH) strategy to engineer stable Cu ADMs on TiO₂ via an ultrafast, millisecond-scale heating-quenching process. This non-equilibrium thermal shock effectively stabilizes the metal species before thermal diffusion can occur, ensuring a robust metal-support interaction as unambiguously confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) analysis. Consequently, the optimized Cu_1.0/TiO₂ delivers an approximately 10-fold enhancement in CO evolution compared to pristine TiO₂ under simulated solar irradiation. Comprehensive in-situ diffuse reflectance Fourier transform spectroscopy (DRIFTS) and photoelectrochemical measurements reveal that these isolated Cu sites function as superior electron-trapping centers, which significantly accelerate interfacial charge transfer kinetics and promote the activation of critical reaction intermediates. This work establishes FJH as a versatile and scalable platform for overcoming the stability-dispersion trade-off in the rational design of high-performance photocatalysts.

Vacancy defect engineering represents one of the most effective strategies for enhancing photocatalytic performance. However, the wide applications of vacancy defect engineering are confronted with the problems of lack of precise control over vacancy defect engineering and poor stability. Herein, we employed an advanced pulse laser ablation in liquid (PLAL) method to introduce sulfur vacancies on the ZnIn₂S₄ nanosheets. Specifically, the vacancy concentration on the ZnIn₂S₄ can be easily modulated by changing the time for PLAL. In addition, it is discovered that the introduction of sulfur vacancies on the ZnIn₂S₄ nanosheets can provide enormous surface-active sites and facilitate the photogenerated charge carrier, thereby enhancing the photocatalytic CO₂ conversion. Compared to the pristine ZnIn₂S₄, the sulfur vacancies-rich ZnIn₂S₄ nanosheets show 15-fold enhancement in photocatalytic CO₂ conversion performance towards CO production, reaching 365 µmol·g⁻¹·h⁻¹. In addition, the sulfur vacancy-rich ZnIn₂S₄ shows a high stability for photocatalytic CO₂ conversion, retaining its performance after 12 h of reaction. According to the mechanistic studies, it is revealed that the sulfur vacancies can also enhance the adsorption capability of ZnIn₂S₄, thereby reducing the potential barrier for subsequent conversion. This work demonstrates the potential of the PLAL strategy for not only precisely introducing vacancy defects on the semiconductors, but also enhancing the stability of the defects, which can pave new avenues for the photocatalytic applications.