Efficient FeCoNiCuPd thin-film electrocatalyst for alkaline oxygen and hydrogen evolution reactions

The creation of high-performing, robust bifunctional electrocatalysts for both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) in water-splitting is crucial for producing emerging hydrogen economy. Here we report a high entropy alloy (HEA) – FeCoNiCuPd – thin film catalyst, which demonstrated excellent alkaline HER and OER performance with ultralow overpotentials as low as 29 mV for HER and 194 mV for OER at a current density of 10 mA cm− 2. The outstanding catalytic activity for HER was found to originate from the multiple active sites present on the FeCoNiCuPd surface, while for OER it came from the highly functional (FeCoNi)-oxyhydroxide species formed on the film surface. Moreover, the two-electrode electrolyzer made of the FeCoNiCuPd film electrodes required a low cell voltage of 1.52 V to achieve 10 mA cm−2 in 1.0 M KOH, greatly outperforming commercially available Pt/C||RuO2 electrodes, while maintaining a notable durability. This work demonstrated the remarkable potential of a HEA thin film in catalyzing water-splitting process.