Coordinate Activation in Heterogeneous Carbon Dioxide Reduction on Co-based Molecular Catalysts

Abstract As CO2 coordination with the metal sites in molecular catalysts represents an effective means to CO2 activation, it is important to develop molecular catalysts with high ability of CO2 coordination to enhance their catalytic performance in CO2 electroreduction. Herein, we investigated the coordinate activation of CO2 with Co-based molecular catalysts by manipulating their ligand structures. During CO2 electroreduction, the current density of Co-salophen for CO was -16.0 mA cm-2 at -0.75 V versus reversible hydrogen electrode (vs RHE), which was 7.6 times of that (-2.1 mA cm-2) of Co-salen. In addition, the Faradaic efficiency (FE) of Co-salophen for CO reached 75% at -0.70 V vs RHE, whereas the FE of Co-salen for CO production was 19%. In-situ experiments and mechanistic studies revealed that both Co-salophen and Co-salen adopted a side-on coordination of CO2 with Co sites. Moreover, the bonding between CO2 and Co sites was strengthened in Co-salophen, resulting in the enhanced activity of Co-salophen.