Flash-thermochemical engineering of phase and surface activity on metal oxides

Abstract

Momentary thermal annealing techniques based on the generation of photo-excited electrons in materials have been applied for ultrafast optical sintering in carbon, metal, and narrow-band-gap black-colored oxides. However, activating the photothermal effect for white-colored oxides is a grand challenge due to their low photothermal conversion efficiencies. Here, we report remarkably enhanced photothermal effects on binary, white-colored tin oxide (SnO2) via a flash-thermal shock (FTS) lamping, which are triggered by low thermal conductivity of polycrystalline nanosheets with abundant defects. These features enable momentary high-temperature annealing (temperature >1,800°C and duration <20 ms) in SnO2 under ambient air. Importantly, the FTS process facilitates thermochemical tuning of crystal structures in bulk SnO2 lattice and the simultaneous ultrafast synthesis of multi-elemental nanoparticles (<10 nm) and/or single-atom catalyst on the host tin oxides. To prove their practical utility, we demonstrated the exceptional chemiresistive gas-sensing capabilities with microelectromechanical systems.