Integrated Capture and Electroreduction of Flue Gas CO₂ to Formate Using Amine Functionalized SnO_<i>x</i> Nanoparticles

Abstract

Flue gas from fossil fuel combustion contributes significantly to CO2 emissions. Due to the low CO2 concentration and the existence of reactive O2 in the flue gas, direct flue gas CO2 electrochemical conversion is a challenging task. Here we integrated both CO2 capture and electrochemical conversion into CO2 enriching catalysts by grafting alkanolamines on a tin oxide surface, which can electrochemically reduce simulated flue gas (SFG, 15% CO2, 8% O2, 77% N2) to formate. Maximum formate Faradaic efficiency of 84.2% has been reached by diethanolamine modified tin oxide (DEA–SnOx/C) at −0.75 V vs RHE with partial current density of 6.7 mA·cm–2 in 0.5 M KHCO3 under simulated flue gas atmosphere. Surface amino groups not only enrich CO2 locally but also inhibit O2 reduction, and in situ infrared (in situ IR) spectroscopy confirmed that amino groups accelerate CO2 reduction by promoting the formation of key intermediates (OCHO–*).