Evaluating the Effect of Oxygen Vacancies on the Oxygen Evolution Reaction (OER) Activity of LaNiO₃

In this work, we have investigated the effect of oxygen vacancies on the surface composition, electronic structure, and oxygen evolution reaction (OER) performance of LaNiO₃. The results show that the OER performance of LaNiO₃ can be improved both by decreasing the oxygen partial pressure during film growth and annealing the thin film in a H₂ atmosphere. X-ray photoemission spectroscopy (XPS) shows a significant increase in the Ni:La ratio on the LaNiO₃ surface after the introduction of oxygen defects, especially after H₂ treatment, where the Ni:La ratio reaches 3.5:1. The presence of oxygen vacancies leads to the aggregation of Ni on the surface of LaNiO₃, which plays a crucial role in enhancing the OER performance of LaNiO₃. In addition, the OER activity of both LaNiO₃ and oxygen vacancy rich LaNiO₃ decreases upon cyclic voltammetry (CV) between 1.0 and 1.5 V versus the RHE with an increase in the cycle number. XPS results reveal that the CV treatments lead to a decrease in the Ni concentration at the LaNiO₃ surface, which is an important factor for the decrease in the OER performance of LaNiO₃ as well as oxygen vacancy rich LaNiO₃.