Customizing pyridinic nitrogen coordination in Ni–N–C for electrocatalytic CO₂ reduction towards CO

Abstract

Nickel anchored N-doped carbon electrocatalysts (Ni-N-C) are rapidly developed for the electrochemical reduction reaction of carbon dioxide (CO2RR). However, the high-performanced Ni-N-C analogues design for CO2RR remains bewilderment, for the reason lacking of definite guidance for its structure-activity relationship. Herein, the correlation between the proportion of nitrogen species derived from various nitrogen sources and the CO2RR activity of Ni-N-C is investigated. The X-ray photoelectron spectroscopy (XPS) spectrum combined with the CO2RR performance results show that pyridinic-N content has a positive correlation with CO2RR activity. Moreover, density functional theory (DFT) demonstrates that pyridinic-N coordinated Ni-N4 sites offers optimized free energy and favorable selectivity towards CO2RR compared with pyrrolic-N. Accordingly, Ni-Na-C with highest pyridinic-N content (ammonia as nitrogen source) performs superior CO2RR activity, with the maximum carbon monoxide faradaic efficiency (FECO) of 99.8% at -0.88 V vs. RHE and the FECO surpassing 95% within potential ranging of -0.88 to -1.38 V vs. RHE. The building of this parameter for CO2RR activity of Ni-N-C give instructive forecast for low-cost and highly active CO2RR electrocatalysts.