Direct Formic Acid Fuel Cell Anode Catalyst

A significant enhancement of catalytic activity toward formic acid electrooxidation has been thought as one of the most challenging problems for the development of direct formic acid fuel cells (DFAFC). In this study, the systematic work focused on preparation methods, support materials and promoters of the catalyst.1. Improved liquid phase reduction method to prepare Pd/C catalyst:the selection of stabilizing agents and the influence of stabilizing agents on the structure of resulting catalysts. (1) According to the mechanism of stabilizing agent and the reported stabilizing agents, we selected CyDTA as the stabilizing agent to prepare Pd/C catalyst. The results showed CyDTA was a superior stabilizing agent. The as-prepared Pd nanoparticles possessed better catalytic activity toward formic acid electrooxidation as a result of the ultrafine particle size and high dispersion. (2) The influence of stabilizing agents on the morphology of Pd nanoparticles on carbon black was extensively investigated. The results exhibited that (a) larger steric hindrance of the stabilizing agent is beneficial to the formation of smaller Pd nanoparticles; (b) chelate complex formation between Pd ions and stabilizing agents can avoid the agglomeration of Pd nanoparticles on the surface of carbon black; and (c) both larger steric hindrance of the stabilizing agent and the chelate complex formation can prevent Pd nanoparticles from deposition in the micropores of carbon black, thus improving its utilization.2. TiO2 as the support material of Pd nanoparticles:the influence of the crystal structure of TiO2 and the improvement of correlative problems. (1) The influence of the crystal structure of TiO2 support material on Pd catalysts for formic acid electrooxidation was investigated. The results showed us rutile TiO2 was a superior support material for Pd nanoparticles. (2) As to the poor electronic conductivity of rutile TiO2, we tried to modify a thin layer of carbon on the surface of rutile TiO2 by adopting the chemical vapor deposition. The results proved this effective method can significantly enhance the catalytic activity of Pd nanoparticles toward formic acid electrooxidation.3. The study of the promoters of Pd/C catalyst:the influence of Co doption and the improvement of the dissolving of the promoter. (1) The influence of Co on the catalytic activity of Pd/C for formic acid electrooxidation was investigated. The results showed that a small amount of Co doption would effectively improve the catalytic activity of Pd nanoparticles on carbon black toward formic acid electrooxidation. (2) Regarding the dissolving of the promoter,such as Fe, we used its carbide (FexC) to alleviate this deficiency. The results exhibited that the application of FexC could significantly enhance the catalytic activity of Pt/C toward formic acid electrooxidation, and avoided the dissolving of Fe.