Desenvolvimento de catalisadores a base de cobre modificados com monoetanolamina para aplicação na redução de CO2

Abstract

The photo and electrochemical conversion of CO2 into higher-value products, such as fuels and chemical precursors, emerges as a promising solution to mitigate carbon emissions and meet the growing global energy demand. However, the viability of these technologies hinges on developing efficient, stable, and cost-effective catalysts. In this work, modified Cu-based catalysts were evaluated for their potential application in the photo and electroreduction of CO2. Aiming to enhance selectivity, reagent availability on the surface, and reduce the reaction overpotential, the studied catalysts were functionalized with nitrogen groups derived from monoethanolamine (MEA), which act as CO2 adducts. The syntheses were conducted by solvothermal reaction and chemical precipitation, both simple techniques involving a single reaction step to obtain the final material. These materials were characterized by various analytical techniques and further applied in CO2 reduction processes. The catalysts synthesized by the solvothermal reaction exhibited compositional variations with copper fractions in different oxidation states, depending on the concentration of added MEA. These catalysts were then assessed for their applicability in the photochemical reduction of CO2, achieving methanol production rates of 1097 µmol g-1h-1, with selectivity greater than 85%. The samples synthesized by chemical precipitation resulted in forming CuO catalysts with different morphologies and crystallite sizes depending on the alkaline agent utilized in the synthesis. The catalyst synthesized with MEA exhibited superior performance in the photoreduction of CO2 compared to catalysts synthesized with other bases (NaOH, KOH, NH4OH), with a methane production rate of 57.2 µmol g-1 h-1. The enhanced activity was attributed to the functionalization of the surface with nitrogen groups. In the electroreduction of CO2, the use of the MEA-functionalized catalyst resulted in current densities of approximately 155 mA cm-2 and stability exceeding 100 hours in long-term tests. The results of this work indicate that functionalization with MEA increases the efficiency of copper-based catalysts in CO2 reduction, both in photochemical and electrochemical processes.