Controllable dispersion of cobalt phthalocyanine molecules on graphene oxide for enhanced photocatalytic CO2 reduction

Abstract

The carbon-based materials with metal-N-C active sites have been widely studied on the electrocatalysis for carbon dioxide reduction reaction (CO2RR), however, they were investigated a few for the photocatalytic CO2RR. Here, cobalt phthalocyanine (CoPc) molecules with intrinsic Co-N4-C moiety are successfully dispersed on graphene oxide (GO) as the CO2RR photocatalyst. The morphology, structure, and component of CoPc/GO composites with the different ratio of GO to CoPc are systematically characterized, confirming the existence of Co-O-C axial coordination bond between CoPc and GO. The optical, photoelectric, and electrical properties of CoPc/GO composites are carefully investigated, indicating their synergistic role of CoPc and GO in photocatalysis. With the optimal CoPc/GO sample as photocatalyst, a ∼1500 μmol⋅g−1⋅h−1 evolution rate and ∼ 85% selectivity of CO and CH4 can be achieved, which is much higher than those performances of CoPc. After the reduction of CoPc/GO to CoPc/rGO, the rate of CO2RR to CO and CH4 is reduced to 916 μmol⋅g−1⋅h−1, indicating the important role of Co-O-C axial bond in the CO2RR. This work provides a simple way to prepare the single-molecule catalyst for CO2RR.