Alkali-Heat Treatment Enhancing Oxygen Tolerance of CO2 electroreduction to HCOOH on SnO2/CN

Tin oxide/carbon nitride composite catalyst (SnO 2 /CN) exhibits high selectivity to CO 2 electroreduction reaction (eCO 2 RR) to HCOOH. However, industry flue gas, with the presence of O 2 and relatively low CO 2 concentration, inhibits the electrocatalytic activity of this kind of catalyst. In this study, alkali-heat treatment was introduced into the pretreatment process of CN carrier to improve the electrocatalytic activity and oxygen tolerance of SnO 2 /CN. The results of X-ray photoelectron spectroscopy confirmed that alkali-heat treatment can expose more surface amino groups of CN, enhancing the alkalinity of composite catalysts and thus the adsorption of CO 2 . Electron transfer occurred significantly from N of alkali-heat treated CN to Sn via enhanced metal-support interaction, forming highly electron-rich centers of Sn species and further benefiting the activation and reduction of CO 2 . The analysis of CO 2 temperature programmed desorption also revealed that alkali-heat treatment could improve binding between catalyst and CO 2 . The multi-component competitive adsorption curve further indicated that alkali-heat treatment was beneficial for CO 2 /O 2 separation as well. Finally, the electrochemical experiments demonstrated that faradaic efficiency (FE) of HCOOH reached 90.5% at a potential of -1.8V (vs. Ag/AgCl) after 2 h of eCO 2 RR over alkali-heat treated SnO 2 /CN. And in the case of simulated industry flue gas, the FE of HCOOH still reached 76.4% with the enhanced oxygen tolerance compared to untreated SnO 2 /CN.