Engineering of atomically dispersed Cu on TiO₂ via flash Joule heating for solar-driven CO₂ reduction

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 bypassed these limitations by developing a facile flash Joule heating (FJH) strategy to engineer stable Cu ADMs on TiO₂ via an ultrafast and 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) analyses. 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.