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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 Ba0.5Sr0.5Co0.8Fe0.2O3 (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. [ABSTRACT FROM AUTHOR]

The Oxygen Evolution Reaction (OER) is crucial in various processes such as hydrogen production via water splitting. Several electrocatalysts, including metal oxides, have been evaluated to enhance the reaction efficiency. Zeolitic Imidazolate Framework-67 (ZIF-67) has been employed as a precursor to produce Co3O4, showing high OER activity. Additionally, the formation of composites with carbon-based materials improves the activity of these materials. Thus, this work focuses on synthesizing ZIF-67 and commercial activated carbon (AC) composites, which were used as precursors to obtain Co3O4/C electrocatalysts by calculating ZIF-67/CX (X = 10, 30, and 50, the mass percentage of AC). The obtained materials were thoroughly characterized by employing X-ray powder diffraction (XRD), confirming the cobalt oxide structure with a sphere-like morphology as observed in the TEM images. The presence of oxygen vacancies was confirmed by infrared spectroscopy and EPR measurements. The electrocatalytic performance in the OER was investigated by linear sweep voltammetry (LSV), which revealed an overpotential of 325 mV at 10 mA cm−2 and a Tafel slope value of 65.32 mV dec−1 for Co3O4/C10, superior in activity to several previously reported studies in the literature and electrochemical stability of up to 8 hours. The reduced value of charge transfer resistance, high double-layer capacitance, and the presence of Co3+ ions justify the superior performance of the Co3O4/C10 electrocatalyst. [ABSTRACT FROM AUTHOR]

The Oxygen Evolution Reaction (OER) is crucial in various processes such as hydrogen production via water splitting. Several electrocatalysts, including metal oxides, have been evaluated to enhance the reaction efficiency. Zeolitic Imidazolate Framework-67 (ZIF-67) has been employed as a precursor to produce Co 3 O 4 , showing high OER activity. Additionally, the formation of composites with carbon-based materials improves the activity of these materials. Thus, this work focuses on synthesizing ZIF-67 and commercial activated carbon (AC) composites, which were used as precursors to obtain Co 3 O 4 /C electrocatalysts by calculating ZIF-67/C X ( X = 10, 30, and 50, the mass percentage of AC). The obtained materials were thoroughly characterized by employing X-ray powder diffraction (XRD), confirming the cobalt oxide structure with a sphere-like morphology as observed in the TEM images. The presence of oxygen vacancies was confirmed by infrared spectroscopy and EPR measurements. The electrocatalytic performance in the OER was investigated by linear sweep voltammetry (LSV), which revealed an overpotential of 325 mV at 10 mA cm -2 and a Tafel slope value of 65.32 mV dec -1 for Co 3 O 4 /C10, superior in activity to several previously reported studies in the literature and electrochemical stability of up to 8 hours. The reduced value of charge transfer resistance, high double-layer capacitance, and the presence of Co 3+ ions justify the superior performance of the Co 3 O 4 /C10 electrocatalyst.