High negative voltage activating perovskite oxide with bi-vacancy synergistic regulation for water oxidation

Abstract

Oxygen vacancy engineering is a strategy to design efficient oxygen evolution reaction (OER) catalysts, but it may lower the band center of O 2p and result in high energy barrier. Here, La0.6Sr0.4Co0.9Fe0.1O3‑δ (LSCF) perovskite catalyst with O and Sr vacancies were prepared by high reduction voltage treatment. The bi-vacancy facilitates the synergistic regulation by providing the inverse movement the d-band center and p-band center to enhance M−O covalency, thus activating lattice oxygen of LSCF. The synergistic effect of Sr and O vacancy reduces the OH adsorption energy on the surface of LSCF, which makes OH adsorption and desorption easier. By optimizing the reduction voltage and time, the overpotential (at 10 mA cm−2) of the high reduction voltage treated LSCF (LSCF- −2V-80 s) is reduced by 130 mV compared to LSCF. The LSCF- −2V-80 s still showed clear lattice fringes after stability test. Moreover, the stronger covalency of LSCF- −2V-80 s to produce O22– intermediates is inclined to be lattice oxygen mediated mechanism (LOM). The bi-vacancy strategy made LSCF- −2V-80 s produce a current density of 174 A/g at 2.50 Vcell in anion exchange membrane water electrolyzer. Bi-vacancy synergistic strategy derived from one-step high reduction voltage provides a new route for OER catalysts.