“…Perovskite oxides with the chemical formula of ABO 3 (A represents alkaline-earth or rare-earth metal ions and B represents transition metal ions) are a class of promising materials to fulfill the aforementioned requirements for field-assisted, and more specifically here, photoassisted LOBs. − Most perovskite oxides are chemically stable, low cost, semiconductive, and structurally tunable at all of the A, B, and O sites, offering a versatile medium to tune the electronic states toward enhanced bifunctionality of ORR and OER, as well as optimized photoresponse for photovoltaics. − Previous studies have shown heteroatomic substitution of alkaline-earth metals at the A site and transition metals at the B site enables modulating both the band structure and spin state of perovskite oxides, apart from creating oxygen vacancies for optimized surface and intermediate-binding energetics. − Specifically for LaCoO 3 (LCO), it was reported that Co ions with the tailored e g spin state close to 1 give rise to the most desired catalytic activities, since electrons on the e g orbits can interact directly with the ligand oxygen and thereby promote electron transfer between surface active sites and adsorbed intermediates. , Thus, enhanced Co 3d–O 2p covalency is beneficial for boosting the intrinsic electrocatalytic activity of LCO for accelerating oxygen cathode reactions. − Specific examples include the partial substitution of La with Sr at the A sites , and substitution of Co with Mn and Fe and at the B sites. However, despite the good electrochemical stability and structural flexibility, the intrinsic catalytic activity and photoactivity of LCO, when deployed as the photocathode catalyst, remain to be further improved.…”