Enhanced electrochemical conversion of CO2 to CO at bimetallic Ag-Zn catalysts formed on polypyrrole-coated electrode

An important strategy for reducing the impact of global CO2 emissions involves conversion technologies that transform CO2 into value-added materials. Bimetallic electrocatalysts of Zn and Ag were constructed on polypyrrole-decorated carbon paper (CP/PPy) electrodes for the improved electrochemical reduction of CO2 to CO. Bimetallic catalysts with different Zn and Ag atomic ratios were produced by the partial galvanic replacement of Zn with Ag on a CP/PPy/Zn electrode. Selectivity for the electrochemical reduction of CO2 to CO at the CP/PPy/Zn/Ag was clearly improved compared to those of the single-metal catalysts (CP/PPy(Ag or Zn)), while the hydrogen evolution reaction (HER) was suppressed. The PPy interlayer between the catalyst and CP support reduced the hydrophobicity of the carbon paper electrode, which facilitated the effective electrodeposition of Ag and Zn on the CP and suppressed the HER at the electrode. Herein, we propose Zn:Ag bimetallic composites deposited on PPy surfaces as CO-selective electrocatalysts with the optimal Zn:Ag catalyst composition suggested by electrochemical and physicochemical analyses. We experimentally confirmed that the atomically mixed Ag-Zn in the bimetallic catalysts enhanced the CO selectivity and production rate over each single metal catalyst. The developed electrocatalyst resulted in a maximum Faradaic efficiency of approximately 70% and a maximum current density of 8.6 mA/cm2 for the CO2 reduction reaction to CO in a 1 M KHCO3 aqueous solution.