Enhanced photocatalytic CO2 reduction with suppressing H2 evolution via Pt cocatalyst and surface SiO2 coating

Abstract The photocatalytic CO2 reduction to chemical feedstocks represents a promising route for the utilization of stranded renewable resources, but faces poor activity and selectivity resulting from the fast recombination of photogenerated charge carriers and competing hydrogen (H2) evolution reaction. Herein, we report the synthesis of core-shell structured Pt/SiO2@SiO2 composites via electrostatic self-assembly and surface SiO2 coating for photocatalytic CO2 reduction with Ru(bpy)32+ (abbreviated as Ru, bpy = 2′2-bipyridine) as photosensitizer and Pt as cocatalyst under visible light irradiation (λ > 420 nm). Photoluminescence results illustrate that Pt cocatalyst enhances the transfer of photogenerated electrons from the excited Ru, thereby improving photocatalytic performance. Further surface coating SiO2 prevents Pt from directly contacting with H2O and ameliorates CO2 adsorption ability of catalyst, thus suppressing H2 evolution and increasing CO selectivity, which also endows the catalyst with enhanced stability. This work would provide an instructive guideline in regulating the selectivity and stability of using transition metal complexes as photosensitizers for photocatalytic CO2 reduction through the cocatalyst loading and surface coating strategy.