Plasmonic Hot Electrons from Oxygen Vacancies for Infrared Light-Driven Catalytic CO₂ Reduction on Bi₂ O_3-x

Current plasmonic photocatalysts are mainly based on noble metal nanoparticles and rarely work in the infrared (IR) light range. Herein, cost-effective Bi₂ O_3-x with oxygen vacancies was formed in situ on commercial bismuth powder by calcination at 453.15 K in atmosphere. Interestingly, defects introduced into Bi₂ O_3-x simultaneously induced a localized surface plasmon resonance (LSPR) in the wavelength range of 600-1400 nm and enhanced the adsorption for CO₂ molecules, which enabled efficient photocatalysis of CO₂ -to-CO (ca. 100 % selectivity) even under low-intensity near-IR light irradiation. Significantly, the apparent quantum yield for CO evolution at 940 nm reached 0.113 %, which is approximately 4 times that found at 450 nm. We also showed that the unique LSPR allows for the realization of a nearly linear dependence of photocatalytic CO production rate on light intensity and operating temperature. Finally, based on an IR spectroscopy study, an oxygen-vacancy induced Mars-van Krevlen mechanism was proposed to understand the CO₂ reduction reactions.