Platinum substituted Cobalt(II, III) Oxide: Interplay of tetrahedral Co(II) sites towards electrochemical oxygen evolution activity

Abstract Substitution of ionic platinum is carried out in Co3O4 host synthesized by solution combustion strategy. These Pt substituted Co3O4 spinels characterized by XRD show pure crystalline phase of Co3O4 without any separated peaks related to Pt/PtOx. Electrochemical OER activities of these spinels are investigated by cyclic voltammetry, linear sweep voltammetry and chronoamperometry in neutral, alkaline and neutral buffer electrolytes. LSV studies on 1% Pt substituted Co3O4 exhibit a low overpotential (η) of 455 mV at 20 mA cm−2 in KOH, as compared to PBS medium. Tafel slope value of 117 mV dec−1 in KOH represents one electron EC mechanism. The detailed XPS studies indicate that Pt doping increases the tetrahedral Co2+ sites of Co3O4. XPS studies before and after the OER also infers that the mixed valence of Co in the host (Co3O4) undergoes redox (Co2+/Co3+) changes with simultaneous reduction in Pt dopant from Pt4+ to Pt2+ influencing the OER activity.