Activation of the Carbon Nitride Surface by Silica in a CO-Evolving Hybrid Photocatalyst

Photocatalytic reduction of CO2 to CO proceeded by visible light (lambda > 400 nm) using mesoporous graphitic carbon nitride (C3N4) coupled with a Ru-II-Re-I binuclear complex (RuRe) containing a photosensitizer and catalytic units. The selectivity to CO exceeded 90% during the initial stage. Photocatalytic reactions (including isotope tracer experiments) and electrochemical measurements revealed that the reaction proceeded according to a two-step photoexcitation of C3N4 and the Ru-II photosensitizer unit, that is, it followed the Z-Scheme mechanism. Modification of C3N4 with highly dispersed silica was found to improve the ability of C3N4 to accommodate RuRe, which enhanced the photocatalytic activity for CO production.