Independent-active-site engineering in N:NiFeP@FeNC electrocatalyst for mitigating HER site oxidation in alkaline electrolysis

Abstract

The performance of the hydrogen evolution reaction (HER) at the cathode in alkaline electrolysis can be compromised due to oxidation caused by the oxygen reduction reaction (ORR), led by oxygen gas crossover through the porous separator. In this study, we introduce N:NiFeP@FeNC, a highly efficient electrocatalyst for HER and ORR in an alkaline environment, featuring independent active sites for each reaction. N:NiFeP@FeNC demonstrated an overpotential of 78 mV to achieve a current density of 10 mA cm-2 for HER and a half-wave potential of 0.88 VRHE for ORR. Notably, the independent HER and ORR active sites effectively prevented oxidation of the HER active site during ORR durability tests. Through density functional theory (DFT) calculations, the mechanisms underlying HER and ORR on N:NiFeP@FeNC were elucidated, identifying key factors that enhance catalytic performance. The low activity of the HER active site (NiFeP) was attributed to the high energy barrier for *H2O dissociation, while the low activity of the ORR active site (Fe-N-C) was related to delayed desorption due to excessively strong interactions between intermediates and the active metal centers. The incorporation of N atoms into the catalyst induced electronic structure reconfiguration in the Ni and Fe atoms, thereby facilitating electrochemical reactions. This study addresses a previously overlooked yet critical issue in alkaline electrolysis cathode research, providing a simple and effective strategy that highlights significance for future exploration.