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

Abstract

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 Fe³⁺ 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 Fe³⁺ 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 ΔG_OH and ΔG_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.