Enhanced Oxygen Tolerance in CO2 Electroreduction to Formic Acid on SnO2/CN Catalyst through Alkali-Heat Treatment

Author(s): Mingxue Su, Zhenguo Guo, Ning Li, and Bing Zhua

The electro-reduction of carbon dioxide (eCO2RR) to formic acid (HCOOH) is very selective while employing the composite catalyst tin oxide/carbon nitride (SnO2/CN). However, the abundance of O2 and the minimal level of CO2 in industrial exhaust gases prevent the catalyst's electrocatalytic activity. The current study employs alkali-heat intervention in the CN payload manufacturing process to increase the electrocatalytic yield and O2 tolerance of SnO2/CN. XPS spectroscopy found that alkali-heat therapy enhances CO2 adsorption and raises the alkaloid level of composite catalyst by revealing a greater percentage of CN's surface amino groups. The improved metal-support contact allowed electrons to flow from the nitrogen of alkali heated CN to tin (Sn), resulting in exceptionally electron-rich Sn species nuclei that facilitated CO2 activation and reduction. A CO2 temperature-designed desorption study showed that the catalyst and CO2 bond more strongly after alkali-heat treatment. A multi-component competitive adsorption curve study indicated more advantages to the alkali-heat process for CO2/O2 separation. Electrolytic studies demonstrated a faradaic efficiency (FE) of 90.5% for HCOOH at a potential of -1.5V (vs. Ag/AgCl) after two hours with alkali heated SnO2/CN. Even in the presence of simulated industry exhaust gas FEHCOOH was 69.4%, showing greater oxygen endurance than untreated SnO2/CN.