Redox sculptured dual-scale porous nickel-iron foams for efficient water oxidation

Metal foams with high surface/volume ratio and excellent electrical conductivity are widely used in water splitting. Herein, we report a redox process sculpturing commercial NiFe foams with dual-scale porosities as high efficient catalysts for water oxidation reactions. Through the oxidation-reduction process, many pores of few micrometres in size were formed on a porous NiFe backbone with a pore size of 50–300 μm. The pore morphology can be reasonably controlled by varying the oxidation temperature. Electrochemical measurement demonstrates that redox-NiFe foam exhibits greatly enhanced activity towards oxygen evolution reaction. Specifically, the redox-NiFe foam oxidized at 900 °C yields the best catalytic activity with an overpotential of 294 ± 3 mV to achieve the current density of 100 mA cm⁻² in 1 M KOH, which is much lower than 402 ± 2 mV of initial NiFe foam. This work highlights the formation of highly porous microstructure in the original skeleton of NiFe foam. Furthermore, the redox sculptured NiFe foams can also function as effective skeletons for the loading of active catalysts, which thus can find wide applications in electrocatalysis and energy storage.