Electroreduction of CO2 catalyzed by Co@N-C materials

A series of Co@N-C materials are synthesized from pyrolysis of ZIF-67 at different temperatures and employed as catalyst for electrochemical reduction of CO 2 (CO 2 RR) to syngas. Through a systematical investigation of the relationship between structure of Co@N-C catalysts and their catalytic activity, it could be found that the Co species exposed on the material surface mainly promote the hydrogen evolution reaction (HER) process to produce H 2 , while the Co particles packaged by N-C skeleton provide electrons and transfer them to CO 2 molecule through the Co -N- C skeleton, promoting the CO 2 reduction reaction. Following this thinking, the pristine Co@N-C materials are treated by aqua regia to remove the surface exposed Co species. After acid treatment, the affinity of H species sharply decreases, and adsorption of CO 2 and transfer of electron to CO 2 are successfully improved. The acid-treated Co@N-C catalysts exhibit improved catalytic activity, faradic efficiency of CO, and stability in CO 2 RR process. Among all these catalysts, the obtained Co@N-C-700-A shows highest CO 2 reduction activity and stability, achieving a specific current of 25 A∙g (cat) −1 and a productivity of 0.266 mol (CO)  h −1 ∙ g(cat) −1 at a mild potential of -0.57 V vs. RHE. The ratio of CO/H 2 in products could be adjusted in the range of 1/4 to 1.5/1.