Active phase formation on Ir-Ru catalysts for the oxygen evolution followed by operando PDF/SAXS

We aim to elucidate the formation of the catalytically active phase of iridium-based oxygen evolving catalysts for proton exchange membrane electrolyzers using operando scattering. Understanding the nature of OER catalysts under operando conditions is crucial to develop optimization strategies reduced Pt group metal (PGM) content. We synthesize small metallic IrxRuy nanoparticles (NPs) of different composition following a previously developed colloidal synthesis route. Thereafter, the NPs are immobilized on two support types, i.e., carbon and antimony doped tin oxide (ATO). Applying potential steps from low to oxidizing potentials we follow the formation of the active catalyst phase. By combining time-resolved operando Pair Distribution Function (PDF) analysis and SAXS measurements we can detect the degree of oxidation, potential Ru dealloying, and amorphization of the NPs, as well as metal dissolution, ripening, and agglomeration at each individual potential applied.