Impact of Surface Defects on LaNiO Perovskite Electrocatalysts for the Oxygen Evolution Reaction.

Perovskite oxides are regarded as promising electrocatalysts for water splitting due to their cost-effectiveness, high efficiency and durability in the oxygen evolution reaction (OER). Despite these advantages, a fundamental understanding of how critical structural parameters of perovskite electrocatalysts influence their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO ; the former exhibit a low onset overpotential of 380 mV at 10 mA cm and a small Tafel slope of 70.8 mV dec . Oxygen vacancy formation is accompanied by mixed Ni /Ni valence states, which quantum-chemical DFT calculations reveal modify the perovskite electronic structure. Further, it reveals that the formation of oxygen vacancies is thermodynamically more favourable on the surface than in the bulk; it increases the electronic conductivity of reduced LaNiO in accordance with the enhanced OER activity that is observed.