Efficient and robust single-layer IrO_x cluster electrocatalyst for oxygen evolution reaction

It is highly desirable to develop efficient and robust oxygen evolution reaction (OER) electrocatalysts for proton exchange membrane water electrolyzer (PEMWE). In this work, an amorphous single-layer IrOx (ASL-IrOx) cluster electrocatalyst is developed by a facile photolysis-electrooxidation strategy for the acidic OER. Experimental results and theoretical calculations indicate that the flexible coordination environment of the cluster gives rise to high-valence Ir5+ species, optimizing the adsorption energy of *OOH and thus improving the OER’s kinetics. As a result, the ASL-IrOx cluster exhibits a 9.9-fold higher mass activity than does the commercial IrO2 catalyst. When applied in a PEMWE, the ASL-IrOx cluster achieves a current density of 1.0 A cm−2 at an electrolysis voltage of 1.64 V and exhibits superior stability up to 200 h at 0.5 A cm−2. This work not only presents a strategy for designing cost-effective catalysts, but also provides crucial insights into the mechanistic understanding of the OER.