Experimental Activity Descriptors for Iridium-based Catalysts for the Electrochemical Oxygen Evolution Reaction (OER)
Spöri, Camillo Wolfgang; Briois, Pascal; Nong, Hong Nhan; Reier, Tobias; Billard, Alain; Kühl, Stefanie; Teschner, Detre; Strasser, Peter
Recent progress in the activity improvement of anode catalysts for acidic electrochemical water splitting was largely achieved through empirical studies of iridium-based bimetallic oxides. However, practical, experimentally accessible, yet general predictors of catalytic OER activity are lacking. This study investigates iridium and iridium-nickel thin film model electrocatalysts for the OER and identifies a set of general ex situ properties that allow the reliable prediction of their OER activity. Well defined Ir-based catalysts of various chemical nature and composition were synthesized by magnetron sput-tering. Correlation of physico-chemical and electrocatalytic properties revealed two experimental OER activity descriptors that are able to predict trends in the OER activity of unknown Ir based catalyst systems. More specifically, our study demonstrates that the IrIII+ and OH-surface concentration of the oxide catalyst constitute closely correlated, and generally applicable OER activity predictors. Based on these, an experimental volcano relationship of Ir-based OER electrocatalysts is presented and discussed.
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