1999 Volume 67 Issue 1 Pages 27-33
The electrocatalytic activity of Zn metal electrode for potentiostatic electroreduction of CO2 has been studied in aqueous solutions of several potassium salts. The reduction products are CO and formate of which faradaic efficiency for formation depend on both the supporting electrolyte and electrode potential. Zn electrode dissolved before the electrolysis in the electrolyte solutions at the rate of 0.85μmol cm−2h−1 in 0.05mol dm−3K2SO4 which is 3.5 times greater than that in 0.1mol dm−3KHCO3 solution. For CO formation, the partial current density is proportional to the CO2 partial pressure and almost independent of pH, the Tafel slope of current-potential curve is ca. 200mV/decade, and reaction orders are ca. 1and 0.5 about CO2 and Zn2+ ion, respectively, in all the potassium salt solutions. On the other hand, in the case of HCOO− formation, the partial current density did not depend on the Zn2+ concentration in the electrolytes.