Scalable surface engineering of commercial metal foams for defect-rich hydroxides towards improved oxygen evolution

The oxygen evolution reaction (OER) is a critical process involved in various energy related processes. Here, surface engineering of metal foams is achieved by immersing a commercially available metal foam in an aqueous Fe(3+)solution at room temperature. This approach provides a facile and scalable one-step strategy to make effective oxygen evolution electrodes, which does not involve any noble metals and does not demand any thermal or electrical energy-intensive steps. The obtained electrodes show low overpotentials of 239-262 mV at 10.0 mA cm(-2)in 1 M KOH for the OER. The spontaneous reaction between Fe(3+)and metallic cobalt or nickel, along with the spontaneous hydrolytic reaction of the metal ions in the presence of air, induces the formation of edge-rich bimetal hydroxide species on the metal foam surface. Importantly, the as-obtained electrodes also demonstrate excellent stability for more than 70 h. Scaled-up preparation of the foam electrodes is shown with the size of an A4 sheet of paper. Density functional theory calculations reveal that the oxygen vacancies induce the structural distortion of M-OH and electronic structure modulation of M-OOH, thus breaking the scaling relation between Delta G(OH)and Delta G(OOH)and improving the catalytic activity. The approach demonstrated here is one of the easy-operation routes for highly active electrocatalytic electrodes towards the OER.