Enhanced photocatalytic CO2 reduction to CH4via restorable surface plasmon and Pdn–Wδ+ synergetic sites

Abstract

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^δ+ 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^δ+ active sites synergistically working with Pd_n sites. The synergy of Pd_n–W^δ+ active sites at the Pd/W₁₈O₄₉ interface enhanced CO₂ adsorption, facilitated proton-coupled electron transfer and stabilized crucial C₁ intermediates. The oxygen vacancies associated with W^δ+ 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 μmol 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.