Customizing pyridinic nitrogen coordination in Ni-N-C for electrocatalytic CO₂reduction towards CO

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-N₄sites offers optimized free energy and favorable selectivity towards CO₂RR compared with pyrrolic-N. Accordingly, Ni-N_a-C with highest pyridinic-N content (ammonia as nitrogen source) performs superior CO₂RR activity, with the maximum carbon monoxide faradaic efficiency (FE_CO) of 99.8% at -0.88 V vs. RHE and the FE_COsurpassing 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.