Replacing precious water oxidation electrocatalysts used in proton exchange membrane (PEM) water electrolyzers with the nonprecious and abundant electrocatalysts is still a poorly addressed issue in the field of hydrogen generation in acidic medium through water electrolysis. Herein we report such an all-nonprecious binary spinel metal oxide the "cobalt titanate" (Co2TiO4) as an efficient alternate to expensive IrO2 and RuO2 for PEM water electrolyzer. The synthesized Co2TiO4 octahedral nanocrystals of size 50 to 210 nm showed excellent oxygen evolution reaction (OER) activity in 0.5 M H2SO4, which was comparable to IrO2 and better than spinel Co3O4 when examined under identical experimental conditions. Overpotential of just 513 mV was sufficient enough to drive a kinetic current density of 10 mA cm-2, which is a significant figure of merit as far as acidic water oxidation electrocatalysis is concerned.
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