(558at) Highly Selective Electrochemical Reduction of CO2 to Formate Via Ultrathin Nanosheet in2S3 in Ionic Liquid

Efficient conversion of greenhouse gas CO₂ into value-added liquid fuels is one of the most promising ways to deal with the excess CO₂ and resolve the energy crisis. Furthermore, it can use renewable electricity to drive the process and the reaction could occur at ambient conditions ^[1]. However, due to the stability of the CO₂ molecule and reaction involves multiple electrons and protons, poor selectivity, low product formation rate and high overpotential are the main challenges of this filed ^[2]. So, efficient catalysts are in great need to break its thermodynamic stability and overcome the kinetically sluggish of reaction.

Indium (In) is a good catalyst for electrochemical reduction of CO₂ to formate (FE > 60%), However, the current density of indium catalysts is usually low, which results in a poor formate formation rate (< 100 μmol h^-1 cm^-2). Recently, it was reported that two-dimensional metal chalcogenides exhibit good activity of electrochemical reduction of CO₂ because of their unique physical and chemical properties. Herein, we carried out the first work on electrochemical reduction of CO₂ to formate using ultrathin nanosheet In₂S₃ prepared by ionothermal synthesis in ionic liquid (IL) electrolyte. The new catalyst exhibited a large formate formation rate and high formate Faradaic Efficiency (FE). The simulation results show that the preferential crystallographic orientation of nanosheet In₂S₃, (311) facet, is more favorable to stabilize the reaction intermediate (OCHO^*) and desorb HCOOH(ads) to form a stable liquid product HCOOH, which is a main reason for excellent performance. This work offers a simple strategy to promote electrochemical reduction of CO₂ performance through changing structure and preferential crystallographic orientation of metal sulfide.

References

[1] Zeng SJ, Zhang XP, Bai L, Zhang XC, Wang H, Wang JJ, Bao D, Li MD, Liu XY and Zhang SJ. Ionic-Liquid-Based CO₂ Capture Systems: Structure, Interaction and Process. Chemical Reviews, 2017, 117: 9625-9673.

[2] Feng JP, Zeng SJ, Liu HZ, Feng JQ, Gao HS, Bai L, Dong HF, Zhang SJ, Zhang XP. Insights into carbon dioxide electroreduction in ionic liquids: Carbon dioxide activation and selectivity tailored by ionic microhabitat. ChemSusChem, 2018, 11: 3191-3197.