Tailoring Lattice Oxygen Binding in Ruthenium Pyrochlores to Enhance Oxygen Evolution Activity
Denis A. Kuznetsov, Muhammad Awais Naeem, Priyank V. Kumar, Paula M. Abdala, Alexey Fedorov, Christoph R. Müller
Abstract
Ruthenium pyrochlores, that is, oxides of composition A2Ru2O7−δ, have emerged recently as state-of-the-art catalysts for the oxygen evolution reaction (OER) in acidic conditions. Here, we demonstrate that the A-site substituent in yttrium ruthenium pyrochlores Y1.8M0.2Ru2O7−δ (M = Cu, Co, Ni, Fe, Y) controls the concentration of surface oxygen vacancies (VO) in these materials whereby an increased concentration of VO sites correlates with a superior OER activity. DFT calculations rationalize these experimental trends demonstrating that the higher OER activity and VO surface density originate from a weakened strength of the M–O bond, scaling with the formation enthalpy of the respective MOx phases and the coupling between the M d states and O 2p states. Our work introduces a novel catalyst with improved OER performance, Y1.8Cu0.2Ru2O7−δ, and provides general guidelines for the design of active electrocatalysts.