Enhanced photocatalytic CO 2 reduction to CH 4 over separated dual co-catalysts Au and RuO 2

A spatially separated, dual co-catalyst photocatalytic system was constructed by the stepwise introduction of RuO 2 and Au nanoparticles (NPs) at the internal and external surfaces of a three dimensional, hierarchically ordered TiO 2 −SiO 2 (HTSO) framework (the final photocatalyst was denoted as Au/HRTSO). Characterization by HR-TEM, EDS-mapping, XRD and XPS confirmed the existence and spatially separated locations of Au and RuO 2 . In CO 2 photocatalytic reduction (CO 2 PR), Au/HRTSO (0.8%) shows the optimal performance in both the activity and selectivity towards CH 4 ; the CH 4 yield is almost twice that of the singular Au/HTSO or HRTSO (0.8%, weight percentage of RuO 2 ) counterparts. Generally, Au NPs at the external surface act as electron trapping agents and RuO 2 NPs at the inner surface act as hole collectors. This advanced spatial configuration could promote charge separation and transfer efficiency, leading to enhanced CO 2 PR performance in both the yield and selectivity toward CH 4 under simulated solar light irradiation.