Catalyst-Support Surface Charge Effects on Structure and Activity of IrNi-Based Oxygen Evolution Reaction Catalysts Deposited on Tin-Oxide Supports

Ir-based nanoparticles supported on conductive oxide supports show high water oxidation (oxygen evolution reaction, OER) activity and represent a promising alternative to state-of-art anode catalysts in water electrolyzers. Physicochemical interactions between the Ir-based catalytic nanoparticles and the oxide supports can critically affect the weight loading, surface area, activity, and stability of the Ir-based catalysts under electrochemical OER conditions. However, systematic insight on the influences of surface charge on deposition yield and dispersion of the nanoparticles on oxide supports and the influence of this interaction on the catalytic performance of supported Ir-based alloys is missing. In this work, the impact of electrostatic interactions between catalyst-support surface charges during catalyst synthesis on the structure and performance of Ir-based OER electrocatalysts is studied. Supported IrNi NPs were synthesized comparing a direct and a stepwise deposition technique onto selected doped tin oxide supports including antimony tin oxide (ATO), In-rich indium tin oxide (ITO), and fluorine tin oxide (FTO), with commercial ATO and unsupported particles as references. Data suggest that electrostatic attractions between particles and supports majorly impact the deposition yield of IrNi NPs. Photoemission spectra, XPS, of supports and supported catalysts show declines in the doping elements concomitant to the variation of the oxide oxidation state. We demonstrate how controlled pretreatments and alterations of repulsive forces between supports and nanoparticles resulted in great improvements in nanoparticle deposition and thus enhanced OER activity. Our findings can be transferred to other nanoparticles/support couples to help improve the distribution and adhesion of the nanoparticles and therefore improve their catalytic performances.