Cobalt Oxide-Supported Pt Electrocatalysts: Intimate Correlation between Particle Size, Electronic Metal–Support Interaction and Stability

Abstract

Oxide supports can modify and stabilize platinum nanoparticles (NPs) in electrocatalytic materials. We studied related phenomena on model systems consisting of Pt NPs on atomically defined Co₃O₄(111) thin films. Chemical states and dissolution behavior of model catalysts were investigated as a function of the particle size and the electrochemical potential by ex situ emersion synchrotron radiation photoelectron spectroscopy and by online inductively coupled plasma mass spectrometry. Electronic metal-support interaction (EMSI) yields partially oxidized Pt^δ+ species at the metal/support interface of metallic nanometer-sized Pt NPs. In contrast, subnanometer particles form Pt^δ+ aggregates that are exclusively accompanied by subsurface Pt⁴⁺ species. Dissolution of Co^<i>x</i>+ ions is strongly coupled to the presence of Pt^δ+ and the reduction of subsurface Pt⁴⁺ species. Our findings suggest that EMSI directly affects the integrity of oxide-based electrocatalysts and may be employed to stabilize Pt NPs against sintering and dissolution.