(519g) Understanding HER/HOR Kinetics through Ru(OH)x Surface Decoration on Pt Single Crystals
In this work, we discuss the role of Ru(OH)x on Pt in alkaline electrolytes. Surface decoration of Ru(OH)x on Pt leads to a dramatic increase in the HER/HOR activity. The improved activity is correlated to a negative shift in the potential of zero total charge (pztc) towards 0 V vs RHE, where the pztc is measured through CO displacement experiments. The negative shift in pztc indicates a higher OHad coverage near HER/HOR relevant potentials. While OHad is not an active participant as we have shown in our previous work , it decreases the activation energy of the hydrogen reactions by bringing water closer to the interface through the OHad-H2Ox-AM+ adducts, as also indicated by Liu et al. . The behavior of Ru(OH)x is also found to display structural sensitivity to the atomic geometry of the underlying Pt substrate, with greater improvements on Pt(111) over Pt(110). Translating this insight to design a highly active nanocatalyst, we synthesize octahedral Pt nanoparticles with a high density of (111)-like domains. Decorating Octa-Pt/C nanocatalyst with Ru(OH)x clusters yields a higher HER/HOR activity than spherical Pt/C + Ru(OH)x, where spherical Pt/C has a higher density of steps, analogous to the Pt(110) surface. Future work involves probing the water mobility and solvent dynamics for a surface decorated with Ru(OH)x. through the kinetic isotope effect.
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