Nanofibras de óxidos mistos de cobalto e manganês obtidas por solution blow spinning (SBS) como catalisadores para reação de evolução de oxigênio

Abstract

The environmental impacts resulting from the indiscriminate use of fossil fuels have driven the search for low-carbon energy sources. In this context, green hydrogen, produced via water electrolysis powered by electricity from renewable sources, emerges as a promising solution for decarbonizing industrial sectors such as ammonia and steel production. However, both half-reactions involved in water electrolysis require efficient catalysts, and the benchmark materials are typically expensive and scarce. Seeking more accessible and abundant alternatives, cobalt- and manganese-based oxides (Co3O4, MnCo2O4, and CoMn2O4), with nanofiber morphology were synthesized via solution blow spinning (SBS) and evaluated as electrocatalysts for the oxygen evolution reaction (OER). The structural, morphological, and surface properties of the materials were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The XRD, FTIR, and Raman results were consistent with those reported in the literature, validating the synthesis and characterization of the materials. Electrochemical characterization for the OER, conducted in 1,0 M KOH electrolyte, revealed that the CoMn2O4, MnCo2O4, and Co3O4 samples exhibited overpotentials of 330, 348, and 375 mV, respectively, to reach a current density of 10 mA cm−2. Cyclic voltammetry and electrochemical impedance spectroscopy further corroborated these findings. The electrodes demonstrated excellent stability, maintaining their performance for up to 20 hours of continuous operation. Detailed surface chemistry analysis via XPS showed that samples with a higher concentration of oxygen vacancies exhibited enhanced charge transfer and higher concentration of reduced Mn species, facilitating the electrocatalysis. These results highlight the potential of cobalt and manganese as viable materials for OER catalyst development.