Pyrrolic N-Stabilized Monovalent Ni Single-Atom Electrocatalyst for Efficient CO2 Reduction: Identifying the Role of Pyrrolic-N and Synergistic Electrocatalysis

Abstract

Engineering the electronic structure of metal, N-doped carbon catalysts is a potential strategy for increasing the activity and selectivity of CO2 electroreduction reaction (CO2RR). However, establishing a definitive link between structure and performance is extremely difficult due to constrained synthesis approaches that lack the ability to precisely control the specific local environment of M-N-C catalysts. Herein, a soft-template aided technique is developed for the first time to synthesize pyrrolic N-4-Ni sites coupled with varying N-type defects to synergistically enhance the CO2RR performance. The optimal catalyst helps attain a CO Faradaic efficiency of 94% at a low potential of -0.6 V and CO partial current density of 59.6 mA cm(-2) at -1 V. Results of controlled experimental investigations indicate that the synergy between Ni-N-4 and metal free defect sites can effectively promote the CO2RR activity. Theoretical calculations revealed that the pyrrolic N coordinated Ni-N-4 sites and C atoms next to pyrrolic N (pyrrolic N-C) have a lower energy barrier for the formation of COOH* intermediate and optimum CO* binding energy. The pyrrolic N regulate the electronic structure of the catalyst, resulting in lower CO2 adsorption energy and higher intrinsic catalytic activity.