Ca₃Co₄O₉-Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ composite catalyst for oxygen evolution reaction

The development of new electrocatalysts for the oxygen evolution reaction (OER) is fundamental for water-splitting devices. In this work, a novel composite based on Ca₃Co₄O₉ (C349) and Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ (BSCF) was synthesized and characterized using XRD with Rietveld refinement, SEM, EDX, and FTIR. The electrochemical properties were evaluated in a KOH alkaline medium. The composite exhibited exceptional OER electrocatalytic activity, showing an overpotential of 389 mV at 10 mA cm⁻², which is lower than the pristine BSCF and C349 samples. Tafel slope of 77 mV dec−1 and double-layer capacitance (Cdl) of 4.37 mF were obtained, indicating an ECSA of 109.25 cm². The composite also demonstrated a high turnover frequency (TOF) of 1.9 × 10⁻³ mol O₂ s⁻¹, underscoring its superior catalytic efficiency. Impedance spectroscopy revealed that the C349 and BSCF samples exhibited greater limitations in charge transfer compared to the composite. These results highlight the composite’s potential as a highly effective OER electrocatalyst, leveraging the synergistic effects of C349 and BSCF.