Functionalizing p-Si/Ag with 2,6-Diaminopyridine for Efficient CO2 Reduction with Enhanced Selectivity at a Low Overpotential

The photoassisted electrochemical CO2 reduction reaction (CO2RR) toward CO is considered one of the most promising routes of CO2 utilization. In this work, 2,6-diaminopyridine (2,6-DAP) with both the pyridine ring and the –NH2 functional group is utilized for the first time to functionalize the surface of the electrode. The p-Si/Ag/2,6-DAP electrode has been identified as a good catalyst with relatively high activity and CO selectivity at a low overpotential as well as good stability. The Faradaic efficiency of CO is 84.56% at an optimized potential of −0.9 V vs reversible hydrogen electrode (RHE). A synergistic mechanism has been proposed for the enhanced catalytic performance of p-Si/Ag/2,6-DAP in the CO2RR. Ag facilitates the reduction of CO2 to produce CO. 2,6-DAP helps CO2 adsorption and inhibits the competitive hydrogen evolution reaction accompanying the CO2RR under low potentials.