Local Electric Field Modulation of Surface Vacancies Enhances CO2 Methanation in Pure Water

Converting CO2 into methane using solar energy, which requires the continuous transfer of eight electrons, presents significant challenges in achieving both high selectivity and a high yield. In this study, we introduce a plasmonic modulation strategy of surface vacancies to enhance the methanation of CO2 in pure water. Using Ag–TiO2 core–shell nanoparticles (NPs) as a model system, we demonstrate that the plasmonic electric field generated by light-excited silver cores permeates the TiO2 shell, globally modulating the reactivity and selectivity of surface vacancies at every site without exception. This achieves fully selective conversion of CO2 to CH4 with a notable efficiency among existing methanation systems. Additionally, the spontaneous interlinking of NPs enhances the local electric field at particle–particle interfaces through cumulative localized surface plasmon resonance, leading to further improvements in activity and selectivity. This cumulative plasmonic enhancement exponentially increases the electric field strength, thereby boosting the photocatalytic performance. Our plasmon-enhanced design underscores the potential of spatially transferring the plasmonic microenvironment toward the outer surface, offering a general strategy to enhance photoactivity and selectivity in photocatalysts.