Produção de hidrogênio de baixo carbono em processos eletrocatalíticos empregando eletrodos modificados com biocarvões

Abstract

A significant challenge in the electrocatalytic hydrogen hydrogen evolution reaction (HER) is to find sustainable options to replace expensive catalysts based on platinum, palladium and other noble metals. The aim of this study was to produce low-carbon hydrogen in electrocatalytic processes, using electrodes modified with biochars from cattle dung and water hyacinth pyrolyzed at temperatures of 400, 500 and 600 °C. In this work, the efficiency of glassy carbon (ECV), carbon paste (EPC) and spongy carbon (ERAM) electrodes were evaluated, when modified with biochar from water hyacinth or cattle dung. The ECV modified with bovine manure biochar obtained at 600 °C (BE6) showed stability during 8000 linear sweep (VL) cycles, a hydrogen generation overpotential of -0.18 V (vs. EPH) after VL cycles, indicating lower energy expenditure due to the composition and morphology of BE6. The Tafel kinetic study showed a value of 25.7 mV dec–1, indicating that the kinetic mechanism follows the Volmer-Tafel. The EPC modified with BE6 remained stable for 200 h under an applied current density of -5.0 mA cm−2, presenting an overpotential of -0.30 V (vs. EPH), with a value of 52.3 mV dec–1, indicating the Volmer-Heyrovsky mechanism. ERAM reduced the corrosion of the steel substrate in 1.00 mol L-1 sulfuric acid, and also showed an increase in current intensity after 2000 scanning cycles and was stable during 220 h of chronopotentiometry. Through electrolysis, stability was observed in acidic solutions, while in basic and saline media, degradation was observed at different potentials. This study contributes to the development of new electrodes and catalyst materials for electrochemical reactions to obtain low-carbon hydrogen with 99% purity. The characteristics observed in the studied electrodes highlight the advantages of using biochars as potential materials for modifying conventional electrodes used for the production of low-carbon H2 from water hydrolysis.