The development of Zn-based electrodes for the CO2 reduction reaction

Abstract

The CO2 levels in the atmosphere are rising due to the use of fossil fuels. Studies showed that using an electrochemical cell the CO2 can be reduced into valuable products. The CO2 reduction reaction takes place on the cathode, made of a transition metal catalyst. The product depends on the transition metal. In this research Zn, Sn and Bi are used to form a trimetallic electrocatalyst for the CO2 reduction. Literature showed that Zn has a main Faradaic efficiency towards CO while Sn and Bi are mainly selective towards formate. The goal was to determine the effect of adding Zn to a Sn- or Bi based electrode to the CO2 reduction, with a main Faradaic efficiency towards formate. The electrocatalysts were synthesized by electrodeposition and characterized before and after catalysis. This led to the conclusion that the addition of 4% Zn to a Sn catalyst is beneficial for suppressing H2 production and scarcely affect the catalyst stability. This effect was not seen with the addition of 32% Zn. The electrode existing of 62% Zn and 38% Bi showed an increase in Faradaic efficiency towards formate at lower cathodic potentials and a decrease in current density. However, this electrode showed some ZnO after catalysis. The trimetallic catalyst showed a lower current density compared to the mono-and bimetallic catalysts. But in terms of stability and selectivity, the addition of Zn to a Sn-Bi electrocatalyst is beneficial to the CO2 reduction reaction, showing a Faradaic efficiency towards formate of 66%.