Hierarchical Fe-doped NiO_x nanotubes assembled from ultrathin nanosheets containing trivalent nickel for oxygen evolution reaction

To design highly efficient and low-cost electrocatalysts for oxygen evolution reaction (OER) is a great challenge for electrochemical water splitting. Herein, we report the preparation of hierarchical Fe-doped NiO_x nanotubes assembled from ultrathin nanosheets with a thickness of 2.4 nm. X-ray photoelectron spectroscopy (XPS) spectra, X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy investigations have been suggested that the incorporation of Fe results in abundant trivalent nickel and nickel vacancies. Benefitting from their unique geometric and electronic structure, the as-prepared hierarchical Fe-doped NiO_x nanotubes exhibit outstanding OER activity and stability, with overpotential of 310 mV and a small Tafel slope of ~ 49 mV dec⁻¹ at 10 mA cm⁻².