Designing IrO₂ Nanoparticles for Oxygen Evolution

IrO2 is one of the most efficient electrocatalyst for the oxygen evolution reaction (OER) and water splitting process for the efficient solar energy into fuel (H2) generation. In solar fuels, IrO2 is used in the form of supported nanoparticles and its catalytic activity strongly depends on the size and shape of nanoparticles. Atomistic modeling of IrO2 nanoparticles with different sizes and shapes can enable fundamental understanding of catalytic processes govern at nanoparticle surfaces. Here, we used density functional theory (DFT) and variable charge force field calculations to study catalytic activity changes at the surfaces, edges and corners on the nanoparticle. We used O adsorption energy as a descriptor for the catalytic activity for water splitting reaction and determined the activity changes with respect to atomic coordination and charge transfer at different active sites on the nanoparticle. Calculations with the developed variable charge force field enable investigation of thermodynamic stability of relatively large (up to 2 nm) IrO2 nanoparticles with different shapes. We construct a metric to describe the overall catalytic activity of a nanoparticle and describe the effects of nanoparticle shape and size on the catalytic activity in terms of surface coordination changes, charge transfer and structural stability. Our results will shed light on the design and development of stable nanoscale IrO2 nanoparticle electrocatalytsts that efficiently utilize solar energy for water splitting reaction. ACKNOWLEDGEMENT: Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.