ELECTROCATALYTIC ACTIVITY OF METALS IN ELECTRO-CHEMICAL REACTION

CO I D22 ii D2 is electrochemically reduced to various products，depending on the electrode metals.Pt can reduce CO I D22 ii D2 to CO strongly adsorbed on the electrode by hydrogen atoms preadsorbed on the electrode.We studied this reaction using high index platinum single crystal electrodes。The activity of the electrodes for the electrochemical reduction of CO I D22 ii D2 depends highly on atomic configuration of the electrode.The activity order is(111)&lt；(997)&lt；(332)&lt；(221)&lt；(110)&lt；(331)&lt；(110)。This order agrees with the step atom density of the electrode surface。We presumed that the hydrogen atoms active for the reaction are the adsorbed hydrogen atoms at the 4-fold sites of the stepped atoms.The electrochemical reduction of CO I D 22 ii was also conducted with platinum electrodes in the electrolyte solution of acetonitrile-water mixtures.The main products are oxalic acid in water free acetonitrile，and formic acid in the electrolyte which contains some concentrations of water.They were obtained continuously from the platinum electrode in spite of the presence of strongly adsorbed CO on the surface.The product selectivity resembles that of Pb and Hg.The machanism was ratinalized in terms of prevention of the adsorption of the CO I D 22 ii anion radical on the electrode surface owing to the strongly adsorbed CO.High index plane single crystals of copper were also studied for the electrochemical reduction of CO ei D 22 ii.The product selectivity is remarkably affected by the crystal orientation of the electrode.(111)surface is favorable for methane formation，and(100)yields more ethylene。We employed some electrodes composed mainly of(100)and small fraction of(111)steps。(711)orientation，composed of 4atomic rows of(100)surface and(111)step gave high ethylene selectivity。The ethylene formation may be activated by the presence of(111)step in(100)atomic configuration。

COィイD22ィエD2 is electrochemically reduced to various products, depending on the electrode metals. Pt can reduce COィイD22ィエD2 to CO strongly adsorbed on the electrode by hydrogen atoms preadsorbed on the electrode. We studied this reaction using high index platinum single crystal electrodes. The activity of the electrodes for the electrochemical reduction of COィイD22ィエD2 depends highly on atomic configuration of the electrode. The activity order is (111) < (997) < (332) < (221) < (110) < (331) < (110). This order agrees with the step atom density of the electrode surface. We presumed that the hydrogen atoms active for the reaction are the adsorbed hydrogen atoms at the 4-fold sites of the stepped atoms.The electrochemical reduction of COィイD22ィエD2 was also conducted with platinum electrodes in the electrolyte solution of acetonitrile-water mixtures. The main products are oxalic acid in water free acetonitrile, and formic acid in the electrolyte which contains some concentrations of water. They were obtained continuously from the platinum electrode in spite of the presence of strongly adsorbed CO on the surface. The product selectivity resembles that of Pb and Hg. The machanism was ratinalized in terms of prevention of the adsorption of the COィイD22ィエD2 anion radical on the electrode surface owing to the strongly adsorbed CO.High index plane single crystals of copper were also studied for the electrochemical reduction of COィイD22ィエD2. The product selectivity is remarkably affected by the crystal orientation of the electrode. (111) surface is favorable for methane formation, and (100) yields more ethylene. We employed some electrodes composed mainly of (100) and small fraction of (111) steps. (711) orientation, composed of 4 atomic rows of (100) surface and (111) step gave high ethylene selectivity. The ethylene formation may be activated by the presence of (111) step in (100) atomic configuration.