Supraparticle Assembly of La_0.8Sr_0.2CoO₃ Nanoparticles for Enhanced Lattice Oxygen Oxidation in Alkaline Electrolysis

Developing effective non-noble metal electrocatalysts for the oxygen evolution reaction (OER) remains challenging due to limited active sites, poor electronic conductivity, and high overpotentials associated with the conventional adsorbate evolution mechanism (AEM). To address these limitations, a one-step spray drying method is employed to assemble high-surface-area La_0.8Sr_0.2CoO₃ nanoparticles (LSCO-NP) into hierarchical supraparticles with ≈65% porosity and interconnected meso-/macropore networks. This architecture not only accelerates ion diffusion and interparticle electron transfer but also induces a mechanistic switch from the AEM to the lattice oxygen oxidation mechanism (LOM). La_0.8Sr_0.2CoO₃ supraparticles (LSCO-SP) demonstrate significantly enhanced OER performance, requiring ∼300 mV lower overpotential at 100 mA cm^-2 after 1 h 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. Structural analyses confirmed that the LSCO-SP maintained their integrity under OER conditions. Furthermore, post-mortem X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analyses reveal an increased formation of oxygen vacancies (O_vac) in LSCO-SP, confirming that the supraparticle design tunes the lattice oxygen-mediated mechanism-oxygen vacancy site mechanism (LOM-OVSM), enhancing OER performance. The hierarchical structure of LSCO-SP highlights their potential as a novel building block for catalyst layers in renewable energy applications.