Boosting electrochemical CO₂ to formate conversion via oxygen vacancy-rich 2D SnO₂ gas diffusion electrodes

Author(s)

Silva, Cleiton P. M. ; Souza, Rafael A. C. ; Marrenjo, Gonsalves J. ; Patrun, David ; Poggere, Leticia ; Canobre, Sheila C. ; Mathur, Sanjay ; Patrocinio, Antonio Otavio T. ; Lopes, Osmando F.

• Document type: Journal article
• Source: JOURNAL OF ELECTROANALYTICAL CHEMISTRY; v. 992, p. 12-pg., 2025-09-01.

Abstract

The development of efficient and earth-abundant catalysts for the electrochemical reduction of CO2 into valueadded products is crucial for the circular economy and mitigation of the greenhouse effect. However, CO2 presents high stability and low solubility in aqueous electrolytes, and efficiency is often limited by CO2 diffusion through the liquid medium to the catalyst surface. This study investigates the combined influence of SnO2 morphology (nanospheres and nanosheets) and oxygen vacancies density in the synthesized oxides on the selective electrochemical reduction of CO2 to formate (HCOO-), employing a flow cell configuration and a gas diffusion electrode (GDE). Under optimized conditions, oxygen vacancy-rich SnO2 nanosheets exhibited the highest CO2-to-HCOO-efficiency, achieving selectivity above 90 %, a current density greater than-200 mA cm-2, and stable operation for 5 h. XPS analysis revealed the coexistence of Sn2+ and Sn4+ species on the surface directly related to the oxygen vacancies, suggesting a key role of the mixed oxidation states in decrease the charge transfer resistance and enhancing catalytic performance. The HCOO-selectivity of SnO2-based catalysts gradually decreased over time at high current densities due to salt deposition and flooding processes. (AU)

• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC