Eletrocatalisador bifuncional baseado em material carbonáceo para geração de hidrogênio e oxigênio de baixo carbono

Abstract

The high cost, scarcity, and limited durability of noble-metal-based electrocatalysts, such as platinum, iridium, and rhodium, have driven the search for alternative materials that are abundant, sustainable, and economically viable for use as catalysts in water electrolysis. In this context, biochar derived from plant residues has emerged as a promising carbon-based material for the development of efficient and environmentally friendly electrocatalysts. This dissertation reports the development of an electrocatalyst based on biochar derived from the aquatic plant Marsilea minuta (BMQ), applied to the hydrogen evolution reaction (HER) in acidic medium and to the oxygen evolution reaction (OER) in alkaline medium. The biochar was prepared by pyrolysis at 500 °C under an inert nitrogen atmosphere and characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results revealed an amorphous structure with a porous surface and the presence of oxygen- and nitrogen-containing functional groups, which act as active sites for electrocatalytic reactions. Electrochemical tests using a glassy carbon electrode modified with the material demonstrated significant activity for both HER and OER, exhibiting low overpotentials required to reach a current density of 10 mA cm⁻² and Tafel slopes consistent with favorable reaction kinetics. Electrochemical stability was confirmed by chronopotentiometry, highlighting the potential of BMQ as a bifunctional electrocatalyst with low carbon emissions. These results indicate that biochar derived from Marsilea minuta is a promising and sustainable alternative for application in water electrolysis systems, contributing to the advancement of low carbon hydrogen and oxygen production technologies.