Stable Water Oxidation Catalysts Based on in-situ Electrochemical Transition of Nickel Phosphate

β-Ni(OH)2 has been synthesized using Ni3(PO4)2 nanowires as precursors by in-situ electrochemical method. X-ray diffraction and selected area electron diffraction displayed that as-prepared Ni3(PO4)2 nanowires were transformed into β-Ni(OH)2 with superlattice structure after activation. It has been found that extremely small size is crucial for the complete conversion of Ni3(PO4)2 and the formation of the superlattice structure. The resulting catalysts by in-situ conversion showed high activity and stability toward oxygen evolution reaction (OER) with an overpotential of 310 mV to reach the current density of 10 mA cm−2 and a long-term stability of 110 h. The large amount of NiOOH in the superlattice structure not only increases the OER activity of β-Ni(OH)2, but also improves the oxidation potential of nickel, thereby decreasing the dissolution. This work proves the feasibility of in-situ electrochemical synthesis for high-performance and stable hydroxide catalysts towards OER.