Adjusting oxygen vacancies in perovskite LaCoO3 by electrochemical activation to enhance the hydrogen evolution reaction activity in alkaline condition

Developing highly-active, earth-abundant non-precious-metal catalysts for hydrogen evolution reaction (HER) in alkaline solution would be beneficial to sustainable energy storage. Perovskite oxides are generally regarded as low-active HER catalysts, due to their inapposite hydrogen adsorption and water dissociation. Here, we report a detailed study on perovskite LaCoO3 epitaxial thin films as a model catalyst to significantly enhance the HER performance via an electrochemical activation process. As a result, the overpotential for the activation films to achieve a current density of 0.36 mA/cm2 is 238 mV, reduced by more than 200 mV in comparison with that of original samples. Structural characterization revealed the activation process dramatically increases the concentration of oxygen vacancies (Vo) on the surface of LaCoO3. We established the relationship between the electronic structure induced by VO and the enhanced HER activity. Further theoretical calculations revealed that the VO optimizes the hydrogen adsorption and dissociation of water on the surface of LaCoO3 thin films, thus improving the HER catalytic activity. This work may promote a deepened understanding of perovskite oxides for HER mechanism by Vo adjusting and a new avenue for designing highly active electrochemical catalysts in alkaline solution.