UC Berkeley

Multimetallic nanomaterials offer a powerful design framework for addressing the intertwined challenges of activity, stability, and cost in the acidic oxygen evolution reaction (OER), which bottlenecks proton-exchange membrane water electrolysis (PEMWE) for green hydrogen (H2) production and other clean-energy electrochemical conversion technologies. This dissertation develops a coherent multimetallic mixing strategy that progresses from entropy-stabilized Ir- and RuIr-based alloys to engineered Ir-free Ru-based oxides. First, IrFeCoNiCu high-entropy alloy (HEA) nanoparticles were prepared via microwave-assisted shock synthesis and demonstrated superior OER performance compared to monometallic Ir and Ir-based binary alloys in acidic media. Post-electrolysis characterization reveals that the 3d metals preferentially dissolve, generating an active Ir-rich oxide shell while the homogeneously mixed HEA core remains intact. The work establishes that OER-induced surface reconstruction is inevitable, even on HEA-based catalysts. Building on this insight, the second work focused on developing a Rux(Ir,Fe,Co,Ni)1−x multicomponent alloy to harness the higher intrinsic activity of Ru while protecting it from rapid dissolution within the multimetallic alloy matrix. OER also induces the formation of a thin stabilized RuIr-rich polycrystalline/amorphous oxide shell upon reconstruction. Machine-learning-based simulations further provide insights into its phase-formation behavior and a predictive map for other well-mixed RuIr-based quinary alloys.Recognizing that the catalytically relevant phase is ultimately a multimetallic oxide, the final study pursues Ir-free engineering of doped RuO2. Systematic screening of 13 transition-metal dopants synthesized via a unified molten-salt platform yields an activity–stability map demonstrating each dopant’s OER performance behavior and identifying Ta and Co as Pareto-optimal candidates for ternary mixing. The resulting Ru0.90Ta0.05Co0.05Ox catalyst achieves synergistic OER enhancements with an overpotential of 189 mV at 10 mA cm−2 , a 16-fold lower dissolved Ru than commercial RuO2, and stable PEMWE operation over 300 hours. This continuous series of work illustrates that multimetallic mixing is a transferable principle across alloy and oxide structures for OER catalysis.