Tunable Oxygen Vacancies Enable Dynamic Infrared Response for Efficient CO2 Reduction on Plasmonic BiOx.

Photocatalytic CO2 reduction offers a sustainable route to convert CO2 into value-added fuels, yet remains limited by poor infrared light utilization. Here, we report a nonmetallic plasmonic BiOx photocatalyst with tunable oxygen vacancies that enable continuous adjustment of infrared absorption from 700 to 1700 nm. By varying calcination temperature, the carrier concentration and localized surface plasmon resonance (LSPR) response are effectively modulated. Combined XPS, Mott-Schottky analysis, and control experiments reveal that gradient oxygen vacancies play a key role in regulating plasmonic intensity and catalytic activity. The optimized BiOx-180°C catalyst achieves efficient CO2 reduction under near-infrared illumination (>800 nm), delivering a total production rate of 3 μmol g-1 h-1 with 50.5% selectivity toward C2 products, which is 2.7 times higher than under UV-Vis light. Moreover, under full-spectrum illumination, BiOx exhibited an increased total product yield, demonstrating the synergistic effect between interband transitions and plasmonic excitations. Quasi-in situ XPS, light-assisted KPFM, and in situ DRIFTS further reveal that the LSPR effect facilitates C-C coupling pathways, promoting the generation of C2 products. This study highlights the potential of dynamic infrared response modulation in plasmonic semiconductors to advance efficient, broadband-driven photocatalytic CO2 reduction.