Investigation of Mechanisms for Electrochemical Catalysis

摘要

A program was conducted to investigate the mechanisms of electrocatalysis with respect to the anodic oxidation of selected fuels by novel electrocatalysts in acid electrolyte at temperatures below 150C and at ambient pressure. A limited number of materials (Interstitial compounds) were screened for corrosion resistance and catalytic activity, but the major emphasis was given to the study of the electrochemical properties of select transition metal silicides, since previous work had indicated some catalytic activity with these materials for fuel oxidation. The effect of surface doping the silicides with trace amounts of platinum and gold was also studied, and in addition the effect of trace amounts of platinum on the catalytic activity of gold surfaces was investigated. The silicides by themselves were found to have only slight catalytic activity for the oxidation of hydrogen or methanol, but, when combined with trace amounts of platinum they showed considerable activity. Investigations on TiSi2, WSi2, MoSi2, VSi2 and TaSi2 showed that their electrochemical behavior was related to crystal structure. Experiments with platinum-doped TiSi2 electrodes indicate that relatively large amounts of platinum are required to obtain a catalytic activity which approaches that of an equivalent platinum sheet and that the utilization of the platinum is low. The oxidation of hydrogen on both smooth gold and gold black gave a limiting current density which decreases at potentials above 250 mv.