Achieving Efficient Electrocatalytic Oxygen Evolution in Acidic Media on Yttrium Ruthenate Pyrochlore through Cobalt Incorporation

Abstract

The development of electrocatalysts for the oxygen evolution reaction (OER) especially in acidic media remains the major challenge that still requires significant advances, both in material design and mechanistic exploration. In this study, the incorporation of cobalt in Y_2-xCo_xRu₂O_7−δ results in an ultrahigh OER activity because of the charge redistribution at e_g orbitals between Ru and Co atoms. The Y1.₇₅Co_0.25Ru₂O_7−δ electrocatalyst exhibits an extremely small overpotential of 275 mV in 0.5 m H₂SO₄ at the current density of 10 mA cm⁻², which is smaller than that of parent Y₂Ru₂O_7−δ (360 mV) and commercial RuO₂ (286 mV) catalysts. The systematic investigation of the composition related to OER activity shows that the Co substitution will also bring other effective changes, such as reducing the bandgap, and creating oxygen vacancies, which result in fast OER charge transfer. Meanwhile, the strengthening of the bond hybridization between the d orbitals of metal (Y and Ru) and the 2p orbitals of O will intrinsically enhance the chemical stability. Finally, theoretical calculations indicate that cobalt substitution reduces the theoretical overpotential both through an adsorbate evolution mechanism and a lattice oxygen-mediated mechanism.