Water Oxidation Catalysts from Waste Metal Resources: A Facile Metal-Organic Electrochemical Approach

A fabrication route is presented by a novel metal-organic electrochemical approach, allowing facile preparation of electrocatalytic metal and metal oxide thin films from solid metals at room temperature: divalent transition metals such as iron, nickel and cobalt can be deposited as amorphous oxyhydroxide films. Among them, nickel- and cobalt-prepared samples are showing high activity as water oxidation catalysts in alkaline electrolytes. The applicability to waste metal material is exemplified using one of the most abundant waste metal alloys, i.e. steel: with a suitable multi-layer architecture, comprising, a large surface-area iron oxyhydroxide core-geometry and a steel-derived catalytic overlayer, the overpotential for oxygen evolution (at 10 mA cm(-2)) could be improved to only 370 mV. Chemical analysis is provided to elucidate the reaction pathway, encompassing metal halogenation, formation of meta-stable metal-organic intermediates or direct electrochemical reduction, respectively. Structural peculiarities of the derived films are finally demonstrated upon development of a photoactive nickel oxyhydroxide/silicon junction realizing a photocurrent of 1 mA cm(-2) at the thermodynamic potential for oxygen evolution and short-term stabilization in the range of several hours.