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Abstract
In this work, we have investigated the effect of oxygen vacancies on the surface composition, electronic structure and OER performance of LaNiO3. The results show that the OER performance of LaNiO3 can be improved both by lowering the oxygen partial pressure during film growth or annealing the thin film in H2 atmosphere. X-ray photoemission spectroscopy (XPS) shows a significant increase in La ratio on the LaNiO3 surface after the introduction of oxygen defects, especially after H2 treatment where Ni/La 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 V and +1.5 V vs. RHE with proceeding cycle numbers. XPS results reveal that the CV treatments lead to the decrease of 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.
