Strategic Assembly of La0.8Sr0.2CoO3 Nanoparticles into Supraparticles for Enhanced Oxygen Evolution in Alkaline Electrolysis

Developing effective non-noble metal electrocatalysts for the oxygen evolution reaction (OER) remains challenging due to limited active sites and poor electronic conductivity in mixed oxide catalysts. To address these limitations, a one-step spray drying method is employed to synthesize hierarchical La0.8Sr0.2CoO3 supraparticles (LSCO-SP) from high-surface-area nanoparticles (LSCO-NP). LSCO-SP demonstrate significantly enhanced OER performance, requiring ~300 mV lower overpotential at 100 mA cm⁻² after 1 hour compared to LSCO-NP. Moreover, LSCO-SP exhibit faster catalytic kinetics, evidenced by a smaller Tafel slope of 76.2 mV dec−1 versus 82.5 mV dec−1 and lower charge transfer resistance of 1.11 Ω versus 1.31 Ω for LSCO-NP. The enhanced activity of LSCO-SP is attributed to their hierarchical porous architecture, which promotes efficient ion diffusion, improved electron transport, and increased accessibility to electroactive sites. Structural analyses confirmed that the LSCO-SP maintained their integrity under OER conditions. Furthermore, postmortem X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses reveal a higher concentration of oxygen vacancies in LSCO-SP, suggesting that the supraparticle design tunes the lattice oxygen mechanism, enhancing OER performance. The hierarchical structure of LSCO-SP highlights their potential as a novel building block for catalyst layers in renewable energy applications.