Desenvolvimento de eletrodos impressos em 3D para aplicação na Reação de Evolução de Oxigênio

Abstract

Recently, there has been significant progress in the search for environmental solutions to the impacts caused by the use of fossil fuels as a primary source of energy, which has led to an increase in interest in efficient technologies that can convert and store energy from renewable sources, especially those that use solar energy to mimic the natural process of photosynthesis, resulting in the production of hydrogen through water electrolysis. However, due to its challenging nature both kinetically and thermodynamically, this artificial photosynthesis process requires the use of stable catalysts to enable the hydrogen evolution (HER) and oxygen evolution (OER) half-reactions to generate H2 and O2, respectively. Furthermore, another challenge lies in the current electrochemical systems, which are made up of high-cost electrodes, thereby increasing the production costs of hydrogen on a large scale. As a result, many studies are being conducted to obtain cheaper and readily available materials as an efficient alternative for these systems. 3D printing has proven to be an excellent tool option for producing conductive printed electrodes, using composite filaments. In this work, electrode modeling and printing were carried out via 3D printer for application in the water oxidation reaction, in addition to the synthesis and characterization of nickel ferrite, NiFe2O4, as an electrocatalyst, and surface modification of the printed electrodes with the synthesized NiFe2O4. Techniques such as X-ray Diffraction, Scanning and Transmission Electron Microscopy, thermal stability and electrochemical analyses were performed to characterize the composite electrode and nickel ferrite. The commercial composite filament used in the work had a composition of 40% (m/m) of carbonaceous material. The data showed the need of activate the printed composite electrodes, which showed promise for use in electrocatalysis. The physically/chemically activated electrodes showed better performance at j = 10 mA cm-2: overpotential (η) of 810 mV in the OER in an alkaline medium, and the lowest Tafel slope values. Nevertheless, the chemically activated electrode provided the lowest resistance to charge transfer (Rp = 115 Ω). Physically activated electrodes need to be further studied because despite their capacitive nature (Rp = 1.45 kΩ), their OER results showed an inverse trend (η = 570 mV).