Electrochemical conversion of CO2 into value-added materials is an important strategy due to the immense contribution of CO2 as a greenhouse gas to global warming. We prepared bimetallic electrocatalysts of Zn and Ag on a polypyrrole-decorated carbon paper (CP/PPy) electrode for improved faradaic efficiency of electrochemical reduction of CO2 into CO and suppressed hydrogen gas evolution from water reduction. The PPy interlayer between the catalysts and carbon paper is utilized to reduce hydrophobicity of the electrode, so to make effective electrodeposition of Ag and Zn to the CP electrode and to suppress HER at the electrodes. The galvanic replacement of Zn in CP/PPy/Zn electrode with Ag atom is conducted to produce bimetal catalysts with different atomic ratios between Zn and Ag. The selectivity of CO2 conversion to CO at CP/PPy/Zn/Ag is obviously improved compared to those of Ag and Zn single metal catalysts with suppressing the hydrogen evolution reaction (HER). Herein, we propose Zn:Ag bimetal composites produced on PPy surfaces as a CO-selective electrocatalyst with an appropriate *COOH binding energy, while an optimal composition of the Zn:Ag catalysts is suggested by electrochemical and physicochemical analyses. We experimentally confirmed that the atomically mixed Ag-Zn in the bimetal catalysts showed enhanced CO2 reduction activity than each metal single catalyst. The developed electrocatalyst results in approximately 70% of maximum Faradaic efficiency and maximum current density of 8.6 mA/cm2 for the CO2 reduction reaction to CO in saturated 1 M KHCO3 aqueous solution.

Electrochemical Conversion of CO2 into CO with Ag-Zn Catalysts Deposited on Polypyrrole Layer

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