Nanostructured perovskite oxides, particularly LaCoO3 and SrIrO3, have emerged as promising electrocatalysts for the oxygen evolution reaction (OER) in water splitting. Their unique crystal structure, tunable electronic properties, and ability to accommodate various dopants make them attractive for optimizing OER activity. The ABO3 perovskite framework allows precise control over composition and defect chemistry, enabling enhancements in catalytic performance through strategic modifications.

Composition tuning via A-site and B-site doping is a critical strategy for improving OER activity. In LaCoO3, partial substitution of La with Sr (La1-xSrxCoO3) introduces mixed valency in cobalt (Co3+/Co4+), enhancing electronic conductivity and creating oxygen vacancies that facilitate proton-coupled electron transfer. Studies show that Sr-doped LaCoO3 achieves overpotentials as low as 390 mV at 10 mA cm−2 in alkaline media. Similarly, B-site doping with transition metals like Fe or Ni can modulate the eg orbital filling of Co, optimizing adsorption energies for OER intermediates. For SrIrO3, A-site deficiency or B-site substitution with less noble metals (e.g., Mn or Cu) reduces Ir usage while maintaining high activity, with reported overpotentials of 280–320 mV in acidic conditions.

Defect engineering further enhances OER kinetics by tailoring oxygen non-stoichiometry and cation vacancies. Oxygen vacancies in LaCoO3-δ act as active sites for water adsorption and dissociation, lowering the energy barrier for O-O bond formation. Controlled annealing under reducing atmospheres can increase vacancy concentrations, improving turnover frequencies (TOF) by up to 5-fold. Cation vacancies, such as La or Co deficiencies, alter the local coordination environment, promoting the formation of highly active surface hydroxides. In SrIrO3, Ir vacancies coupled with strain effects from epitaxial growth on substrates like SrTiO3 can stabilize Ir4+ states, which are more active than Ir3+ for OER.

Exsolution phenomena, where doped cations migrate to the surface under reducing conditions, create metal nanoparticles embedded in the perovskite matrix. For example, Ni-doped LaCoO3 can exsolve Ni nanoparticles upon thermal treatment, forming heterostructures that enhance charge transfer and provide additional active sites. These exsolved particles improve stability by preventing perovskite phase segregation during prolonged OER operation. In SrIrO3, exsolved Ir nanoparticles exhibit strong metal-support interactions, mitigating Ir dissolution in acidic media while maintaining TOF values above 0.1 s−1.

Stability remains a significant challenge, particularly in acidic media where SrIrO3 suffers from Sr leaching and Ir dissolution. Strategies like surface passivation with amorphous carbon or doping with refractory metals (e.g., Ta) can extend catalyst lifetimes beyond 100 hours at pH < 3. In alkaline conditions, LaCoO3 faces gradual Co oxidation and phase transformation to CoOOH, which, while active, reduces long-term durability. Hybrid architectures, such as LaCoO3 coated with conductive oxides like Sn-doped In2O3, mitigate degradation by preserving the perovskite phase.

Performance benchmarks highlight the trade-offs between activity and stability. LaCoO3-based catalysts typically achieve overpotentials of 350–450 mV in 1 M KOH, with TOFs ranging from 0.01 to 0.05 s−1. SrIrO3 systems outperform in acidic media (overpotentials of 280–350 mV in 0.5 M H2SO4) but require careful compositional optimization to balance cost and durability. Recent advances in nanostructuring, such as creating porous LaCoO3 nanofibers or ultrathin SrIrO3 nanosheets, further reduce mass transport limitations and expose more active sites, pushing overpotentials closer to the theoretical minimum.

Key considerations for future development include scaling synthesis methods to maintain nanostructural fidelity and elucidating degradation mechanisms through in situ characterization. The interplay between dopants, defects, and exsolved phases offers a rich design space for next-generation perovskite OER catalysts, with potential breakthroughs in efficiency and cost-effectiveness for industrial water splitting.