Metallized Ni(OH)2·NiO/FeOOH on Ni foam as Highly Effective Water Oxidation Catalyst Prepared by Surface Treatment: Oxidation-Corrosion Equilibrium

The surface treatment method has a great influence on the structure and properties of applied materials for interface catalysis. In this study, we prepare Ni(OH)₂·NiO/FeOOH by surface treatment in acid solution using oxidation-corrosion equilibrium (OCE). For comparison, we also treat Ni foam with the same process in alkaline solution. Ni(OH)₂·NiO/FeOOH can arrive steady-morphology and metallization by oxidation-corrosion equilibrium and exhibits superior catalytic activity as water oxidation catalyst. Ni(OH)₂·NiO/FeOOH(OCE) needs only 232 mV to reach a current density of 10 mA cm^-2, while it is 254 mV for a reference IrO₂/Ni foam. The mechanism study shows that the small charge transfer resistance (2.04 Ωcm²) is favorable for the rapid interface electron exchange between Ni(OH)₂·NiO/FeOOH(OCE) and reactive species in water oxidation. In addition, the results of X-ray photoelectron spectroscopy and series impedance show that the catalyst is metallic property in virtue of exposed mental Ni in Ni(OH)₂·NiO/FeOOH(OCE). The volume ratio of hydrogen to oxygen (about 2:1) indicates overall water splitting by the double electrode system. When the volume ratio of hydrogen to oxygen is 2:1, the Faraday efficiency of H₂ or O₂ is close to 100%. Ni(OH)₂·NiO/FeOOH(OCE) exhibits good stability for one month. The research results provide a feasible approach for finding low cost metallized catalysts to replace noble metal as water oxidation catalysts and improving the efficiency of water splitting.