Experimental Activity Descriptors for Iridium-Based Catalysts for the Electrochemical Oxygen Evolution Reaction (OER)

Abstract

Recent progress in the activity improvement of anode catalysts for acidic electrochemical water splitting is largely achieved through empirical studies of iridium-based bimetallic oxides. Practical, experimentally accessible, yet general predictors of catalytic OER activity have remained scarce. 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 sputtering. Correlation of physicochemical 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. On the basis of these predictors, an experimental volcano relationship of Ir-based OER electrocatalysts is presented and discussed.

Recent Progress in Electrocatalysts for Acidic Water Oxidation

“…[ 132 ] The structure and composition of bimetallic oxides can be modulated by a variety of synthesis methods, including thermal decomposition and sputtering techniques. [ 133,134 ]…”

Electrolyte Effects on the Electrocatalytic Performance of Iridium‐Based Nanoparticles for Oxygen Evolution in Rotating Disc Electrodes

“…The identification and rigorous comparison of promising catalysts is essential for the rational design and development of more active and stable OER catalysts for PEM electrolysers. Due to an evident need to overcome this problem, recent studies have reported protocols and recommendations for the evaluation of the OER in acidic media, as well as Ir‐based catalysts for this reaction . Only few of them focus on the effect of the experimental parameters ( e. g .…”

Pt Dopant: Controlling the Ir Oxidation States toward Efficient and Durable Oxygen Evolution Reaction in Acidic Media

“…[ 3 ] An amorphous form of electrochemically oxidized Ir (Ir III ) with the hydrated or hydroxylated structure has exhibited the highest catalytic activity among various material phases, owing to the flexible structure of catalytic sites. [ 4–6 ] Unfortunately, such Ir III oxides eventually worsen the OER performance because high potentials promote the oxidation and dissolution of active Ir during long‐term operation. [ 7–9 ] Meanwhile, Geiger et al showed that the rutile structure in IrO 2 (Ir IV ) exhibits much higher stability than amorphous Ir III oxides.…”