Selective Conversion to Formic Acid from CO2 By Electrochemical Reduction over Cuxsny Intermetallic Compounds

Abstract

Electrochemical reduction of CO2 is of high value because it can reduce the amount of greenhouse gas in the atmosphere. However, since CO2 is a very stable compound due to the strength of C=O bonds, it is extremely hard to turn CO2 into other compounds. In addition, potassium bicarbonate, which is commonly used as electrolyte for electrochemical CO2 reduction, decomposes on most catalysts to form hydrogen (H2) by reduction of proton (H+) at the potentials required to reduce CO2. Therefore, it is important to use a catalyst that prevents the H2 evolution reaction. Widely studied electrocatalysts for electrochemical CO2 reduction are novel metals, such as Pd, Ag and Au, because they can efficiently reduce the CO2 to CO in high selectivity with low overpotentials. Although non-precious metals such as Zn, Sn and/or Bi are promising as the electrocatalysis for the CO2 reduction, using them require high overpotentials and also result in the formation of H2. Sn electrode is a viable candidate for CO2 reduction catalyst because it shows relatively high selectivity towards formation of formate. However, Sn demonstrates a function towards H2 evolution reaction. In order to overcome this problem, we have attempted alloying of Sn with Cu which can modify the electronic state and crystal structure of active site of Sn. In this study, we successfully prepared CuxSny intermetallic nanoparticles supported on carbon, which not only significantly improved the electrocatalytic activity of CO2 reduction, but also showed a highly selective conversion to formic acid. The structural difference of surface between Sn and SnCu, which corresponds to the high activity and selectivity towards CO2 reduction reaction, is also discussed in this poster session.