Band structure engineering of Pd, Rh, Cu-Modified SrMoO4 for enhanced activity and selectivity in photocatalytic CO2 reduction to CH4

Abstract

Photocatalytic CO2 reduction holds promise as a strategy to mitigate the energy crisis and greenhouse effects. However, devising cost-effective photocatalysts capable of efficiently and selectively converting CO2 to CH4 remains challenging. This study presents the synthesis of Pd, Rh, and Cu-modified SrMoO4 photocatalysts via a one-step solvothermal method. Our findings demonstrate increased CH4 activity and controlled selectivity through the modification with Pd, Rh, or Cu ions. It was determined that Pd, Rh, or Cu ions modified the SrMoO4 surface as -O-Pd-O-, -O-Rh-O-, or -O-Cu–O- species, increasing the adsorption sites and active regions on the catalyst surface. Moreover, these introduced -O-Pd-O-, -O-Rh-O-, or -O-Cu–O- species' energy level enhances visible light absorption and photogenerated charge carrier separation, and regulates the band structure for better alignment with water oxidation potential. This leads to greater water oxidation half-reaction efficiency and increased H+ generation in photocatalytic CO2 reduction. Consequently, more protons (H+) participate in CO2 photocatalytic reduction, thus promoting CH4 production and selectivity. These insights may guide the design of highly-selective photocatalysts for effective CO2 photoreduction through bandgap engineering strategies.