Electroreduction of Carbon Dioxide on Copper Modified with Imidazole-Derived Molecules: Investigation of Activity and Stability in Single-Cell Electrolyzers

• Grant number: 24/22351-4
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: July 01, 2025
• End date: June 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Fabio Henrique Barros de Lima
• Grantee: Lucas Destefani Paquini
• Host Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 19/22183-6 - Electrocatalysis VI: fundamental and applied aspects of emerging and classical problems in electrochemical energy conversion, AP.TEM

Abstract

The CO2 Reduction Reaction (CO2RR) into higher value-added products for industry stands out as an essential alternative for a sustainable scenario, especially when powered by electricity from "green" sources. The selective formation of multi-carbon (C2+) products has garnered significant interest both at laboratory and industrial scales due to the demand for higher energy density fuels. For this purpose, to date, only copper-based electrocatalysts have demonstrated the ability to form hydrocarbons and alcohols. However, several factors limit their direct application in CO2RR, such as high overpotential, low selectivity and faradaic efficiencies due to parallels reactions, such as the Hydrogen Evolution Reaction (HER), and, above all, low stability, primarily due to the dynamic structural behavior of copper. To address these issues, two different strategies have been applied: (i) Induction of dynamic behavior in a controlled manner using stable organic ligands that enable the coordination of copper ions and the in situ formation of metallic nanoparticles; and (ii) Inhibition of dynamic behavior through chemical adsorption of molecules or polymers, stabilizing surface copper atoms. For the second strategy, imidazole (I), benzimidazole (BI), and polybenzimidazole (PBI) stand out due to their high stability under CO2RR conditions. Furthermore, Imidazole groups act as basic sites with various functions. They contribute to complex formation or coordination, maintaining copper stability, altering the electronic structure of the metal, and facilitating the hydrogenation of CO2RR intermediates, favoring the formation of C2+ products. Based on the above, this research project aims to study the electrochemical reduction of CO2 on copper (Cu) electrocatalysts modified with molecules containing imidazole groups, such as Polybenzimidazole (PBI), in single-cell systems operating under practical conditions (acidic anolyte and a solid-state membrane electrolyte). At the cathode, CO2RR will be conducted on nanostructured copper-imidazole-based electrocatalysts (e.g., Cu-PBI), obtained from the coating of copper nanoparticles and the reduction of Cu(II) coordination polymers with ligands containing imidazole and benzimidazole groups. At the anode, the Oxygen Evolution Reaction (OER) will be carried out on Dimensionally Stable Anodes (composed of Iridium, Tin, and Tantalum). Various operational parameters will be investigated, such as the influence of applied current, the concentration of the anolyte, and the evaluation of activity and faradaic efficiency for the reaction products. Techniques such as gas chromatography (GC), high-performance liquid chromatography (HPLC), and mass spectrometry (MS) will be used to determine the reaction products, while the electrodes will be structurally and electrochemically characterized. Additionally, in situ techniques, such as Raman spectroscopy and X-ray Absorption Spectroscopy (XAS), will provide insights into the formation of intermediates (Raman) and changes in electronic and structural characteristics of the electrocatalyst before, during, and after electrolysis. The ultimate goal is to elucidate the optimal operating conditions for the single-cell system with a solid-state electrolyte, focusing on maximizing the production of high-value-added C2+ products.