Cobalt‐Vanadium Hydroxide Nanoneedles with a Free‐Standing Structure as High‐Performance Oxygen Evolution Reaction Electrocatalysts

Abstract It is a great challenge to develop electrocatalysts with high efficiency and low cost toward oxygen evolution reaction (OER) for the electrolysis of water. Herein, novel CoV‐hydroxide nanoneedle arrays with freestanding structure is successfully fabricated as new electrocatalysts for OER. Remarkably, the incorporation of V into Co hydroxide can significantly modulate the nanoneedle morphology, which results in the increase of active surface area, and augment the intrinsic activity by tuning the electronic structure. Particularly, we find that the freestanding Co hydroxide nanoneedles with 25 % Co substituted by V (Co 0.75 V 0.25 ‐HNNs) show the optimum OER catalytic activity and have a low overpotential (268 mV at 10 mA cm −2 ), a small Tafel slope (80 mV dec −1 ) and long‐term stability, which are comparable to the other Co‐based and V‐based electrocatalysts for OER reported in literature.