Gas diffusion electrode preparation 85 mg as-prepared catalyst, 300 mg Nafion solution (Sigma-Aldrich, 5wt% Nafion in ethanol solution), 100 μL DI-water and 2900 μL isopropanol were mixed and sonificated using sonifer horn for 15 mins. The prepared ink was sprayed coated onto the commercial gas diffusion electrode provided by DeNora (GDL2), on the micro porous layer, at 80 °C.