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

Photocatalytic CO₂ reduction offers a sustainable route to convert CO₂ into value-added fuels, yet remains limited by poor infrared light utilization. Herein, a nonmetallic plasmonic BiO_x photocatalyst with tunable oxygen vacancies is reported that enables 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 X-ray photoelectron spectroscopy (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 BiO_x-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, BiO_x exhibits an increased total product yield, demonstrating the synergistic effect between interband transitions and plasmonic excitations. Quasi-in situ XPS, light-assisted Kelvin probe force microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy 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.