Problems Related with Experimental Procedures and Data Analysis

Problems Related with Experimental Procedures and Data Analysis 

Eyring and his coworkers studied the kinetic process of CO2 reduction at a Hg electrode mainly on the basis of their current potential measurements. Since the cathodic current corresponds accurately to CO2 reduction in the neutral pH region, the reaction kinetics can be discussed on the basis of the current potential relation. 

Many subsequent workers studied CO2 reduction at various metal electrodes, employing voltammetric or polarization measurements. They judged that the electrochemical reduction of CO2 proceeded when the cathodic current under CO atmosphere was higher than that under inert atmosphere. The net CO2 reduction current was often determined as the difference between the two cathodic currents w ith and without CO2. The assumptions made in this procedure were that the current in CO2 saturated solution is a sum of CO2 reduction current and HER current, and that HER cm-rent in CO2 saturated solution takes the same value as that in inert gas saturated solution. 

Two problems are pointed out for this procedme. One is that the two cathodic currents, HER and CO2 reduction, are sometimes involved with each other, when CO2 reduction actually takes place. For example, a Cu electrode is covered with adsorbed CO during the reduction of CO2 to CH4 or other hydrocarbons in an aqueous 

Thus papers which report CO2 reduction only on the basis of the difference current will not be discussed any more. 

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