Effect of metal electrode

Reduction of carbon dioxide takes place at various metal electrodes. The main products are formic acid in aqueous solutions and oxalate, CO, and formic acid in nonaqueous solutions. An indium electrode is the most potential saving for C02 reduction. Due to the difference in optimum conditions between those for C02 reduction to formic acid and those for formic acid reduction to further reduced products, direct reduction of C02 in aqueous solutions without a catalyst to highly reduced products seems to be difficult at metal electrodes. However, catalytic effects of metal electrodes themselves have recently become more clear for example, on Cu, methane was detected, while on Ag and Au, CO was produced effectively in aqueous solutions. Furthermore, at a Mo electrode, methanol was obtained. The power efficiency is, however, still low at any electrode. 

Mihailetchi V. D., Koster L. J. A. and Blom P. W. M. (2004), Effect of metal electrodes on the performance of polymer fullerene bnlk heterojunction solar cells , Appl. Phys. Lett. 85, 970-972. 

---