Enhanced Photocatalytic CO2 Reduction to CH4 Via Restorable Surface Plasmon and Pdn-Wδ+ Synergetic Sites

The solar-driven conversion of CO2 and H2O to hydrocarbons is highly desirable; however, it remains a great challenge due to the difficult activation of CO2 and H2O molecules, insufficient supply of electrons and protons, and inadequate stabilization of crucial intermediates. This work developed a Pd nanoparticle (Pd-n)-modified W18O49 photocatalyst and demonstrated an intriguing preactivation strategy for the Pd/W18O49 catalyst to restore surface plasmon and low-valent W delta+ sites based on the photochromic behavior of W18O49. The optimized preactivation process resulted in significant enhancements in both activity and selectivity of the Pd/W18O49 catalyst for photocatalytic CO2-to-CH4 conversion, owing to the excellent light-harvesting ability across the solar spectrum and abundant W delta+ active sites synergistically working with Pd-n sites. The synergy of Pd-n-W delta+ active sites at the Pd/W18O49 interface enhanced CO2 adsorption, facilitated proton-coupled electron transfer and stabilized crucial C-1 intermediates. The oxygen vacancies associated with W delta+ sites on W18O49 intensified the adsorption and activation of H2O molecules. Moreover, the plasmon-induced thermal effect accelerated the reaction kinetics of crucial elementary steps during the photocatalytic CO2 reduction process, resulting in a high production rate of 27.27 mu mol g(cat)(-1) h(-1) and a remarkable selectivity of 94.1% for CH4 generation without requiring any sacrificial agent. This research provides novel insights into the development of semiconductor photocatalysts for efficiently converting CO2 and H2O into fuels through harnessing solar energy.