PULSED ELECTROREDUCTION OF CO2 ON COPPER ELECTRODES .2.

The pulsed method newly developed by the present authors was applied t o electroreduction of CO2 on Cu electrodes. It was found that the opti mum cathodic bias for generating CH4 and C2H4 was - 2.6 V vs. SCE, and the optimum anodic bias for the generation of C2H4 was slightly more anodic than that of CH4. Total faradaic efficiency eta(HC) for the gen eration of CH4 and C2H4 became a maximum at 10-degrees-C and reached a bout 65%. Furthermore, eta(HC) increased with increasing reduction tim e in strong contrast with the conventional potentiostatic electroreduc tion in which eta(HC) decreased drastically with the reduction time du e to the poisoning effect of the products. It was proposed that some s urface intermediate formed by the interaction between CO2 and the thin oxide layer on a Cu electrode is finally reduced to CH4 or C2H4, depe nding on the anodic reactions taking place during the anodic period.