Palladium and cobalt complexes of substituted quinoline, bipyridine and phenanthroline as catalysts for electrochemical reduction of carbon dioxide

The complexes of [M(PPh3)(2)L]X (M = Pd, Co; L = substituted quinoline, bipyridine and phenanthroline, and X = Cl, Br or ClO4) have been found to be an electrocatalyst for the reduction of CO2 in acetonitrile (AN) and AN-water (8% for volume) solutions containing 0.1M tetraethylammonium perchlorate (TEAP) at a glassy carbon or Pt electrode. The complexes working as the catalyst were [M(PPh3)(2)L]X[L = 2-methyl-8-hydroxyquinoline (2-m-8-Hq), 2-quinoxalinol (2-Qui.), 1-hydroxyisoquinoline (1-Hiq), 3-hydroxyisoquinoline (3-Hiq), 4,4'-Dimethyl-2,2'-bipyridine (4,4'-dim-2,2'-Bipy) and 4-methyl-1,10-phenanthroline (4-m-1, 10-Phen)] at the applied potential of -1.30 V vs Ag/10 mM Ag+. Under anhydrous conditions, CO was a dominant product with the current efficiency of 83% and the amount was independent of the kind of the catalysts. In the AN-water solution, however, the reduction products were CO and HCOOH in addition to H-2. (C) 1997 Elsevier Science Ltd.