Key roles of surface Fe sites and Sr vacancies in the perovskite for an efficient oxygen evolution reaction via lattice oxygen oxidation

Abstract

The oxygen evolution reaction via lattice oxygen oxidation (LOER) on perovskite catalysts has attracted great interest recently because of its low reaction energy barrier. However, as the surface structure of perovskites is dynamic during catalysis, the active sites and contributing factors of the LOER are still unclear, which seriously limits the development of efficient perovskite catalysts. Herein, by using a flexible etching method, we design and fabricate highly efficient La/Sr-based perovskite catalysts with surface Fe sites and Sr vacancies for the LOER and establish a relationship between the LOER and dynamic surface structure. Theoretical calculations and advanced in situ characterizations, such as in situ X-ray absorption near edge structure (XANES) and in situ Raman, have demonstrated that surface Fe sites act as catalytic centers for the LOER, while Sr vacancies can promote the LOER by upshifting the oxygen 2p levels. Furthermore, the time-of-flight secondary ion mass spectroscopy (tof-SIMS) and differential electrochemical mass spectrometry (DEMS) results reveal that the LOER on perovskites is realized by lattice oxygen dynamic changes via the adsorbed ¹⁶OH transforming to Co–¹⁸O–¹⁶O in the ¹⁸O isotope labeling experiment. The synthesized La/Sr-based perovskite catalyst shows superior OER catalytic performance, which is higher than that of the RuO₂/C catalyst. This work not only proves the key roles of surface Fe doping and Sr dynamic dissolution in achieving an efficient LOER, but also paves the way for design of high-performance perovskite catalysts.