Surface Treatment, Alloying and Modification of Cu Electrode

Modifications of Cu electrode have been reported with introduction of oxygen, sulfur, or chlorine atoms to the surface in order to improve the product selectivity. 2.222 jj jg confirmed whether or not these atoms still remain on the electrode surface during electrolytic reduction of CO2. These atoms would be removed from the surface by cathodic polarization during the electrolysis, and newly reduced Cu surface may be composed of crystallites with favorable atomic configurations for preferred selectivity. 

Product Distribution in CO2 Reduction at a Series of Copper Single-Crystal Electrodes, Cu(S)-[w(100) x (111)] and Cu(S)-[w(lOO) X (110)]. Reprinted from Ref. 91, Copyright (2003) with Permission from Elsevier 

Several reactions proceed competitively at copper electrodes, and the electrocatalytic activity for the individual reactions depends on the atomic configuration of the electrode surface. Thus fundamental study using single cry stal electrodes is relevant to reveal the unique electrocatalytic naUires of copper metal. Frese reported that CH4 formation in the electrochemical reduction of CO2 is favored in the order of Cu(lll). Cu(llO) and Cu(lOO). Later Hori et al. extensively studied the reaction with various series of Cu single crystal electrodes.  

Atomic configurations of some Cu crystal orientations are unstable, and easily reconstmcted during surface pretreatment, e.g. by the presence of oxygen and ultrasonic rinsing in the pretreatment procedme and so on. Cu(llO) is particularly vulnerable among various Cu single crystal orientations, and the selectivity in CO2 reduction on Cu(llO) is hardly reproducible. Takahashi et al. 

Electrolyte solution 0.1-M KHCO3 current density 5 mAcm.  

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