<i>In Situ</i> Probe of the Hydrogen Oxidation Reaction Intermediates on PtRu a Bimetallic Catalyst Surface by Core–Shell Nanoparticle-Enhanced Raman Spectroscopy

Abstract

<i>In situ</i> monitoring of the evolution of intermediates and catalysts during hydrogen oxidation reaction (HOR) processes and elucidating the reaction mechanism are crucial in catalysis and energy science. However, spectroscopic information on trace intermediates on catalyst surfaces is challenging to obtain due to the complexity of interfacial environments and lack of <i>in situ</i> techniques. Herein, core-shell nanoparticle-enhanced Raman spectroscopy was employed to probe alkaline HOR processes on representative PtRu surfaces. Direct spectroscopic evidence of an OH_ad intermediate and RuO_<i>x</i> (Ru(+3)/Ru(+4)) surface oxides is simultaneously obtained, verifying that Ru doping onto Pt promotes OH_ad adsorption on the RuO_<i>x</i> surface to react with H_ad adsorption on the Pt surface to form H₂O. <i>In situ</i> Raman, XPS, and DFT results reveal that RuO_<i>x</i> coverage tunes the electronic structure of PtRuO_<i>x</i> to optimize the adsorption energy of OH_ad on catalyst surfaces, leading to an improvement in HOR activity. Our findings provide mechanistic guidelines for the rational design of HOR catalysts with high activity.