Electrode Metals and CO Selectivity

Such a classification obtained from the selectivity in aqueous systems is combined with that in nonaqueous systems shown in Table 6, resulting in Table 8. CO formation metals in aqueous electrolyte yield CO in PC. Some formate formation metals in aqueous electrolyte, Hg, Tl and Pb, give oxalic acid in PC. The intermediate metals. Cd, Sn, and In, give CO in PC solutions as the major product, whereas formic acid in aqueous solutions. 

Classification of Electrode Metals in Accordance with Product Selectivity in CO2 Reduction in Aqueous and Nonaqueous Electrolyte (PC). Reproduced from Ref. 23, Copyright (1994) with permission from Elsevier 

The presence of small amount of foreign atoms on the electrode surface changes greatly the reaction selectivity of CO2 reduction, as exemplified by metal electrodes alloyed with other metals or adatom modified electrode. Adatom modified electrodes were prepared by underpotential deposition (UPD) or overpotcntial deposition techniques. The coverage of the adatoms ranged between 1.1 and 1.6, mostly between 1.25 and 1.35. CO selectivity r in CO2 reduction, defined as F(CO)/[F(CO) + F(HCOO)], was 

Substrate metal Potential (Vvs. SHE) Without adatoms Cd With adatoms Tl 

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