Dual plasmonic coupling effect in Bi/vacancy-rich Bi₂WO₆ heterojunction for selective CO₂ photoreduction to CH₄

Low-cost plasmonic semiconductors with high density of free carriers have attracted increasing attention in photocatalytic CO₂ reduction (PCR), since they display the localized surface plasmon resonance (LSPR) to improve the light-harvesting and produce hot electrons to boost the PCR activity. However, the produced hot electrons in plasmonic semiconductors are easily suppressed to limit the enhancement of the PCR performance. Herein, the dual plasmonic coupling system of Bi nanoparticles/vacancy-rich Bi₂WO₆ nanosheets (BWO-Vo-Bi) is designed and constructed. An intense plasmonic coupling induced by metal Bi and plasmonic semiconductor of vacancy-rich Bi₂WO₆ is formed, thus contributing to a strong full-spectrum solar absorption and fast charge transfer in BWO-Vo-Bi heterojunction. The significant enhancement of light absorption and charge movement further accelerates the generation of high-energy hot electrons and extends the lifetime of photogenerated electrons, thereby yielding a high CH₄ evolution rate of 20.36 μmol g^-1 h⁻¹ with a selectivity of 93.0 % in BWO-Vo-Bi under light irradiation without sacrificial agents, which is 55 times higher than that of Bi₂WO₆. This work provides a new strategy for the development of high-performance photocatalysts for CO₂ reduction through dual plasmonic coupling.