Regulating oxygen vacancy distribution in perovskites via A-site cation engineering for water oxidation

Abstract

Oxygen-deficient perovskite oxides hold great potential as highly efficient catalysts for the oxygen evolution reaction (OER), but the effective regulation and in-depth understanding of oxygen vacancies (Vos) remain a challenge. This study reports perovskite oxides with different A-site cations (LaCoO₃, SrCoO_x, and CaCoO_2.5) that successfully regulate the distribution of oxygen vacancies and that different oxygen vacancy distributions lead to distinct surface reconstructions and catalytic mechanisms during the OER. Vo-deficient LaCoO₃ shows minimal reconstruction and maintains an active crystalline CoOOH phase at lower potentials, but its performance degrades at higher potentials due to Co(OH)₂ formation. SrCoO_x, with irregular oxygen vacancies, undergoes surface amorphization to active CoOOH, which promotes catalytic efficiency. CaCoO_2.5, with ordered vacancies, forms localized amorphous active CoOOH zones only under higher potentials. LaCoO₃ exhibits a lattice oxygen mechanism, and proton transfer is not involved in the rate-determining step. In contrast, irregular Vos in SrCoO_x and ordered Vos in CaCoO_2.5 switch the reaction pathway to the adsorbate evolution mechanism and involve proton transfer in their rate-determining steps, which is more significant for CaCoO_2.5 with increased potential for the OER. These findings underscore that the extent and type of surface reconstruction, driven by oxygen vacancy distribution, critically influence the reconstruction to the active phase and electrocatalytic mechanism for the OER. The study offers new insights into tailoring surface vacancy configurations to optimize catalyst design for an efficient OER, advancing the development of cost-effective electrocatalysts for sustainable energy applications.