Intrinsic activity and mechanistic insights in LaCoO₃ OER catalysts induced by support material

• Four electrode supports were examined for their influence on catalytic behavior: Nickel (Ni), Iridium (Ir), Platinum (Pt), and Glassy Carbon (GC). The intrinsic activity trends (at 10 mA cm⁻²) varied significantly with the type of support. • FTIR analysis showed changes in *–OH adsorption and interfacial water structure, indicating possible shifts in the OER mechanism depending on the support. • Differences in acceptor concentration were observed across different supports, highlighting electronic interactions between the LCO and electrode materials. • Changes in Co oxidation states and surface oxygen species were most notable on Ni. It suggests OER may proceed via a lattice oxygen mechanism on certain supports. The oxygen evolution reaction (OER) is an essential half-reaction in electrochemical energy conversion in aqueous media and a key to achieving improved water splitting efficiency. Perovskites, such as lanthanum cobalt oxide - LaCoO 3 , are a promising materials due to their activity and stability in alkaline conditions. The present study focused on and investigated the influence of the electrode support on the intrinsic activity of the LaCoO 3 perovskite catalyst towards OER. Nickel, iridium, platinum, and glassy carbon electrodes were used as electrode support for the assessment of the support effects. The trend in the overpotential at 10 mA cm -2 recorded by linear sweep voltammetry reveals a difference in the electrochemical behavior based on the support material used. In all cases, the coated electrode presented higher OER activity compared to the bare support electrodes, which indicates the active participation of the catalytic LCO in the reaction. In-situ Fourier-transform infrared spectroscopy showed that *–OH adsorption and interfacial water structure, suggesting possible shifts in the OER mechanism. Besides, in situ Raman provided insights regarding the influence of the support on the Co oxidation. Further insights were obtained from electrochemical impedance spectroscopy and Mott-Schottky analysis, where a differences in the acceptor concentration on different electrode supports was observed. X-ray photoelectron spectroscopy, performed before and after electrochemical measurements, revealed changes in Co oxidation states and surface oxygen species, particularly significant on the Ni electrode, which may be attributed to the OER proceeding through the lattice oxygen mechanism. These findings highlight the crucial role of the support electrode during OER, emphasizing the importance of catalyst-support interactions in electrocatalyst design.