Ternary Zn-Ce-Ag catalysts for selective and stable electrochemical CO2 reduction at large-scale

Abstract

Catalyst materials with high stability and selectivity, based on inexpensive materials, are vital for practical electrochemical carbon dioxide (CO2) reduction (ECR). In this study, we report ternary Zn-Ce-Ag catalysts for selective and stable CO2-to-CO conversion at high current densities on a large scale. We found that ZnO catalysts are relatively selective for CO2-to-CO conversion, but are only stable for less than 20 h at current densities over 100 mA cm−2 due to the reduction of the Zn oxide phase, along with the ECR. Combining ZnO with CeO2 significantly improves the stability of the catalysts, maintaining a CO Faradaic efficiency (FECO) of 80 % for 100 h at the current density of 200 mA cm−2. By introducing a small amount of silver (<10 wt%) to form ternary Ag-Ce-Zn catalysts, both CO selectivity and stability are significantly improved: the developed catalysts exhibit a high FECO of 90 % at 200 mA cm−2 and are stable for 200 h. We attribute the enhanced CO2-to-CO conversion efficiency to the abundance of stable interfacial areas of various metal-oxide interactions, which are critical for ECR. To demonstrate the potential for practical application, we performed the ECR in a large electrochemical cell, with an active surface area of 100 cm2. The system delivers a FECO of 90 % at 200 mA cm−2 for an extended operation time of 200 h.