Microwaves assisted synthesis of IrRu alloy nanoparticles for acidic oxygen evolution reaction: A balance between activity and stability

• Ir and Ru based alloys were synthesized through a facile MW-NaBH 4 reduction method. • In the OER characterizations, Ru promoted activity while Ir ensured stability. • The best combination is Ir-Ru (50:50) of 425 A g −1 activity and 50 % retained current stability. Under the background of renewable hydrogen generation through proton exchange membrane water electrolysis, here we report highly efficient and stable iridium (Ir) and ruthenium (Ru) alloy based electrocatalysts for the acidic OER. The electrocatalysts were synthesized by a facile microwave-assisted sodium borohydride (MW-NaBH 4 ) reduction method with 98 % reaction conversion efficiency. The ultrafine IrRu alloy nanoparticles have shown transfer of electron from Ru to Ir and d -band structure modification. Benefiting from the electron transfer between the active metals, the synthesized electrocatalysts have exhibited superior OER performance in acidic electrolyte. Among the combinations, the Ir-Ru (30:70) demonstrated mass activity as high as 481 A g −1 and requiring overpotential of 270 mV to deliver a current density of 10 mA cm −2 , better performance compared to other synthesized and commercial electrocatalyst. Further, Ir-Ru (50:50) have exhibited the best OER performance of 425 A g −1 mass activity, double to that of commercial IrO 2 and retained around 50 % of their initial current density (IrO 2 remains only 31 %) in long-term AST tests. Based on the solution electrochemical performance such as low overpotential (310 mV vs . 330 for IrO 2 ), high mass activity and long-term stability the Ir-Ru (50:50) alloy combination can be considered a promising electrocatalyst for PEMWE applications.