Structural investigation of metallic Ni nanoparticles with N-doped carbon for efficient oxygen evolution reaction

Abstract Developing cost-effective electrocatalyst for oxygen evolution reaction (OER) and elucidating the structural transformation is urgent but remains a significant challenge. Here, we report a scalable approach to prepare well-defined Ni nanoparticles supported by nitrogen-doped carbon (Ni/NC), which possess superior catalytic activity and durability for OER, especially for the sample pyrolyzed at 600 °C. Moreover, the dynamic surface reconstruction of as-prepared catalysts during OER was detailedly investigated by ex-situ characterizations and operando X-ray absorption spectroscopy combined with the difference method that is a novel technique to probe the subtle structural changes. Our findings demonstrate that a surface oxidation to Ni(OH)2 on Ni nanoparticles occurs at the beginning of OER, and then a reversible phase transitions between Ni(OH)2 and NiOOH depends on the applied potential. Thus, this work develops a new method for preparing low-cost Ni-based electrocatalyst and sheds light on the direct observation of surface structure evolution during the OER.