Morphology modulation and surface reconstruction of the NiFeSe arrays during long-term OER process at large current densities

Developing catalysts with long term stability at large current densities for oxygen evolution reaction (OER) remains a major challenge. Herein, the NiFeSe arrays were synthesized on the commercial nickel-iron foams (NFF) substrate using a one-step hydrothermal method by changing the hydrazine hydrate to solvent volume ratio in the precursors and reaction temperature. The NiFeSe/NFF catalyst prepared at the hydrazine hydrate to solvent volume ratio of 1:4 and reaction temperature of 160 °C shows the optimal OER electrocatalytic performance with a low overpotential of 245, 259 and 269 mV at the current density of 100, 200 and 300 mA cm −2 , small Tafel slope of 44.7 mVdec −1 and large electrochemical surface area (ECSA) of 600 cm 2 in 1 M KOH solution. Importantly, the OER activities of the NiFeSe/NFF catalyst exhibit enhancement during long-term stability test at a bias of 1.04 V (vs. Hg/HgO) for 327 h. During long-term continuous OER electrochemical process , the formation of NiFeOOH/NiFeSe heterojunction resulting from the surface reconstruction are responsible for enhancing OER activities by modulating the electron structure of interface and increasing the adsorption ability of intermediate *OH and *OOH on the surface of NiFeOOH. Our work provides new idea to design and construct heterostucture catalyst via the in-situ surface reconstruction.