Synthesis of nanostructured β-Ni(OH)2 by electrochemical dissolution-precipitation and its application as a water oxidation catalyst

synthesize nanostructured beta-Ni(OH)(2) powders (particle size 10-100 nm, specific surface area similar to 100 m(2) g(-1)) from Ni metal anodes. The approach differs from existing electrochemical synthesis methods in that it predominantly results in bulk precipitation of nanoparticles, without significant film growth on either of the electrodes. Heat treatment of the as-synthesized beta-Ni(OH) 2 afforded NiO with mostly preserved nanostructure and very high specific surface area (<= 100 m(2) g(-1), depending on calcination temperature). The as-synthesized beta-Ni(OH)(2) was found to be an excellent catalyst for the oxygen evolution reaction (OER) in the technologically important water electrolysis process, apparently contradicting recent reports that the alpha polymorph is required for such high activity. With catalyst loadings < 0.1 mg cm(-2), OER current densities of 10 mA cm(-2) were sustained at overpotentials as low as 340 mV, with Tafel slopes of only similar to 38 mV/decade. The catalyst was highly stable in alkaline media over the course of electrolysis experiments lasting for several hours. This performance surpasses that of many previously reported earth-abundant OER catalysts and is comparable to that obtained with stateof- the-art RuO2 and IrO2 catalysts.