(334g) Core-Shell Nanoparticles for Efficient Oxygen Evolution Electrocatalysis in Alkaline and Acidic Media

By storing excess renewable energy in chemical bonds, water electrolyzers provide a promising means of renewable energy storage and clean hydrogen fuel generation toward a sustainable energy infrastructure. Currently, the slow kinetics of the oxygen evolution reaction (OER) occurring at the electrolyzer anode limit device efficiencies, necessitating the development of high performance electrocatalysts. Core-shell and surface-leached nanostructures provide promising strategies to achieve enhanced OER catalysis through electronic and geometric structure alterations. This presentation will explore these strategies in alkaline and acidic electrolyte through the discussion of two model systems: Au@M_xO_y (where M=Ni, Co, Fe, and CoFe) core@shell nanoparticles for alkaline OER and surface-leached crystalline strontium iridate nanostructures for acidic OER. In alkaline media, the beneficial effects of Au-supported catalysts were translated to core-shell Au@M_xO_y nanoparticles, demonstrating a universal activity enhancement with the inclusion of the Au-core. The highest activity particles, Au@CoFeO_x, demonstrated an overpotential of 328 ± 3 mV over a 2 h stability test at 10 mA cm^-2, illustrating that strategically combining Au support and mixed metal oxide effects in a core-shell nanoparticle architecture is a promising avenue for practical catalyst design. In acidic media, the effect of crystal structure and stoichiometry on the activity and stability of crystalline strontium iridate (e.g. Sr₂IrO₄, SrIrO₃, and Sr₄IrO₆) nanostructures is evaluated in comparison to commercial Ir/C nanoparticles. In-situ leaching results in an IrO_x-rich surface on a strontium iridate core. Detailed microscopy and spectroscopic evaluation before and after electrochemistry is provided to elucidate performance trends and highlight structure-activity-stability relationships. These two systems demonstrate the potential catalytic benefits of core-shell motifs resulting from both direct chemical synthesis and post-synthetic in-situ modification towards the OER in alkaline and acidic electrolyte.