Constructing Surface Plasmon Resonance on Bi₂WO₆ to Boost High-Selective CO₂ Reduction for Methane

Plasmonic Bi₂WO₆ with strong localized surface plasmon resonance (LSPR) around the 500-1400 region is successfully constructed by electron doping. Oxygen vacancies on W-O-W (V1) and Bi-O-Bi (V2) sites are precisely controlled to obtain Bi₂WO₆-V₁ with LSPR and Bi₂WO₆-V₂ with defect absorption. Density functional theory (DFT) calculation demonstrates that the V1-induced energy state facilitates photoelectron collection for a long lifetime, resulting in LSPR of Bi₂WO₆. Photoelectron trapping on V1 sites is demonstrated by a single-particle photoluminescence (PL) study, and 93% PL quenching efficiency is observed. With strong LSPR, plasmonic Bi₂WO₆-V₁ exhibits highly selective methane generation with a rate of 9.95 μmol g^-1 h^-1 during the CO₂ reduction reaction (CO₂-RR), which is 26-fold higher than 0.37 μmol g^-1 h^-1 of BiWO₃-V₂ under UV-visible light irradiation. LSPR-dependent methane generation is confirmed by various photocatalytic results of plasmonic Bi₂WO₆ with tunable LSPR and different light excitations. Furthermore, the DFT-simulated pathway of CO₂-RR and in situ Fourier transform infrared spectra on the surface of Bi₂WO₆ prove that V1 sites facilitate CH₄ generation. Our work provides a strategy to obtain nonmetallic plasmonic materials by electron doping.