Recently, team of Prof. Dehui Deng in the State Key Laboratory of Catalysis of our institute made a new progress in the electrocatalytic CO2 reduction reaction (CO2RR) to CO using well-defined metal-N4 sites. This work has been published as a communication in Angew. Chem. Int. Ed. entitled “Understanding the reaction mechanisms of well-defined metal-N4 sites in electrocatalytic CO2 reduction” (Angew. Chem. Int. Ed. DOI: 10.1002/anie.201808593).
Metal-containing nitrogen-doped carbon (metal-N-C) has been found exhibiting promising electrocatalytic activity for CO2RR to CO. However, due to the great challenge in controllable synthesis of uniform and well-defined metal-N-C structures, the active sites and the reaction mechanisms are still under debate and need to be clarified. In addition, the optimum metal-N-C catalyst for CO2RR is still not determined. Based on the previous work of the research team in studying metal-N4 active sites and the related catalytic reactions (Sci. Adv. 2015, 1, e1500462；Nat. Nanotechnol. 2016, 11, 218；Angew. Chem. Int. Ed. 2016, 55, 6708；Nano Energy 2017, 32, 353; Chem 2018, 4, 1902), metal phthalocyanines (MePcs) with well-defined metal-N4 structures were used as model catalysts to study the underlying active centers and reaction mechanisms of electrochemical CO2RR, combining density functional theory calculations, electrochemical experiments and in situ XAS characterizations. Both theoretical and experimental studies identify CoPc as the optimum catalyst for selective CO2RR to CO among all the MePc candidates. The Co site in CoPc serves as the active center and its high activity for CO2RR originates from the moderate *CO binding energy on the Co site which accommodates the *COOH formation and the *CO desorption. The optimized CoPc catalyst can achieve a maximal Faradaic efficiency of 99%, and maintains a long-term stability.
This study clearly illustrates the active center, reaction mechanism, and the activity trend on these well-defined metal-N4 sites, and paves a way towards rational design of highly efficient metal-N-C electrocatalysts for CO2RR.
This work was conducted in collaboration with Dr. Jianping Xiao from Westlake University, Prof. Zhongqun Tian and Prof. Ye Wang from Xiamen University, and Prof. Rui Si from Shanghai Institute of Applied Physics, Chinese Academy of Sciences. This work is supported by Ministry of Science and Technology of China, National Natural Science Foundation of China, Key Research Program of Frontier Sciences of the Chinese Academy of Sciences, and Collaborative Innovation Center of Chemistry for Energy Materials (2011. iChEM). (Text and Image by Zheng Zhang and Hehua Gao)