Effects of Cationic Species in Electrolyte Solution

The cationic species also affects the CO2 reduction at metal electrodes. Paik et al. studied electroreduction of CO2 to HCOO at a Hg pool electrode in Li , Na and (C2H5)4N hydrogen-carbonate solutions. The electrode potential at a constant current increases in the positive direction with the sequence of Li Na (C2H s)4N . The results were discussed in connection with the vari- 

The features of CO2 reduction at a Cu electrode also depends remarkably on cationic species. Table 14 shows faradaic efficiencies of CO2 reduction at a Cu electrode in 0.1 M various alkali hydrogen-carbonate solutions at a constant current density 5.0 mA cm Hydrogen formation is prevalent in the Li electrolyte. 

The formation of C2H4 and alcohols increases relatively in the order Li Na I Cst The CH4 and C2H4 ratio in the faradaic efficiency C1/C2 obviously shows a trend Li Na iC Cs.  

The potential during the electrolysis is in the order Li Na I Cs. An identical feature appears in electrochemical reduction of CO, an intermediate species in CO2 reduction. Such a cationic effect in CO2 reduction at a Cu electrode was confirmed by Kyriacou and Anagnostpoulos, and by Ohta and his coworkers with methanol based electrolyte solutions.  

The cationic effect may be derived from the extent of the specific adsorption of the cations. The hydration number of LT is the highest, and that of Cs is the lowest among these 4 alkali cations. Cs, the largest and softest among these cations, is more easily 

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