Flue gas produced by fossil fuel combustion contributes significant amount of CO2 emission. However, the CO2 concentration in flue gas is only 6~15%, and separation of CO2 from flue gas suffers from high energy consumption and multiple steps. Direct electro conversion of flue gas to value-added products is a promising approach for mitigating environmental issues and renewable energy storage. Due to the low CO2 concentration and existence of reactive O2 in the flue gas, direct flue gas electro utilization suffers from low efficiency. Herein, we integrate CO2 capture and conversion into one system by introducing amine molecules on tin oxide surface which can electrochemically reduce simulated flue gas (SFG, 15% CO2, 8% O2, 77% N2) to formate. In 0.5 M KHCO3 electrolyte, the maximum formate Faradaic efficiency (FEHCOO-) of 84.2% has been reached by diethanolamine modified tin oxide (DEA-SnOx/C) with partial current density of 6.7 mA cm-2 (jHCOO-) at -0.75 V vs. RHE. Based on the Lewis acid and base interaction, the amino groups in the surface amine molecules with high CO2 adsorption capacity create a local enrichment environment for CO2 and the amino groups on electrocatalysts could change the binding energy of reaction intermediates, promoting CO2 electroreduction kinetics. Moreover, surface molecules block O2 transportation to the tin oxide surface then the O2 reduction reaction (ORR) can be inhibited. The in situ infrared (in situ IR) spectroscopy proved that amino groups in the surface amines accelerate CO2 reduction by promoting the formation of key intermediates. Surface functionalization of tin oxides by amines could capture and transform CO2 in a single system, offering a simplified pathway for utilization of flue gas CO2.

Direct capture and electroreduction of flue gas CO2 to formate using amine functionalized SnOx nanoparticles

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.