Surface electron modulation of a plasmonic semiconductor for enhanced CO2 photoreduction

Abstract

In plasmonic semiconductors, the presence of a surface depletion layer, where the electron density rapidly decreases, hinders their application in photocatalysis. Herein, plasmonic Bi₂WO₆ nanodots (BWO-NDs) with oxygen-vacancy-induced electron-trapping states were controllably grown on TiO₂ nanosheets (TO-NSs) as plasmonic heterostructures for enhanced photocatalysis. UV-visible light-excited electrons on both TO-NSs and BWO-NDs were collected on the nanodots to modulate their surface electron density, leading to the strongest surface plasmon resonance (SPR) in 5 s. Moreover, the surface electron modulation broke the limitation of the surface depletion layer on hot electron generation of plasmonic BWO-NDs. Therefore, during the CO₂ reduction reaction (CO₂-RR), the optimal 15%-BWO-ND/TO-NS heterostructure generated 57.6 μmol g⁻¹ methane with a selectivity of 75% in 3 h, which is over 12- and 5-fold higher than that of TO-NSs and plasmonic Bi₂WO₆, respectively. Moreover, the oxygen vacancies on the plasmonic BWO-NDs acted as active sites for CH₄ generation. Our work provides an effective strategy to modulate the surface electron density of plasmonic semiconductors for enhanced photocatalysis.