Tailoring electronic structure of Ni-Fe oxide by V incorporation for effective electrocatalytic water oxidation

Tailoring the electronic structure of metal active sites of catalysts and understanding the corresponding mechanism of enhanced oxygen evolution reaction (OER) performance are required to engineer advanced OER catalysts. Herein, we first report that the electron interaction between Ni/Fe sites and V dopants in Ni-Fe oxides deposited on nickel foam by reactive magnetron co-sputtering can be stimulated by vacuum annealing. The subsequent annealing at 300 °C promotes the electron transfer from Ni to V, while the annealing at 400 °C significantly facilitates the electron transfer from Fe to V. The best NiFeV0.65-A4 (NiFeV0.65 annealed at 400 °C) electrode with the optimized V-incorporated amount achieves a low overpotential of 248 mV at 10 mA/cm2 and a durable stability for 130 h. Besides, we demonstrate more intuitively the occurrence of OER self-reconstruction process to derive metal oxyhydroxides on the surface of catalysts. The mechanism studies manifest that V incorporation not only affords a larger electrochemicalsurface area, but also particularly tailors the electronic structure of both Fe3+ and Ni3+ sites. The density functional theory calculations indicate that the synergetic effect between Ni and Fe induced by V incorporation can promote the formation of *O intermediates under OER to enhance the OER intrinsic activity.