Impact of Surface Defects on LaNiO3 Perovskite Electrocatalysts for the Oxygen Evolution Reaction

Abstract

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 influences their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO 3 perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO 3 induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO 3 ; the former exhibit a low onset overpotential of 380 mV at 10 mA.cm -2 and a small Tafel slope of 70.8 mV.dec -1 . Oxygen vacancy formation is accompanied by mixed Ni 2+ /Ni 3+ valence states, which quantum-chemical DFT calculations reveal modify the perovskite electronic structure. Surface oxygen vacancy formation is relatively facile, and favoured over lattice vacancy formation, and increases the electronic conductivity of reduced LaNiO 3 , in accordance with the enhanced OER activity observed.