Preparation Of Pd-based Catalyst Supported On Titanium Carbide And Its Catalytic Performance For Formic Acid

Formic acid possesses a high power density,storage safety,non-toxicity and non-flammability and other characteristics.At present,more and more attention is attracted to the direct formic acid fuel cells in the field of hybrid cars and portable power.The anodic catalyst plays a key role in the direct formic acid fuel cells.Pd-based catalyst is considered to be the preferential anodic catalyst for the direct formic acid fuel cells due to its lower price relatively and a stronger resistance to poisoning of CO,which is the perfect anodic catalyst for the direct formic acid fuel cells.Nevertheless,the stability of Pd-based catalysts should be greatly improved.The catalyst supports are essential for improving the activity and stability of the catalyst.The researches of supports mainly focus on the novel non-carbon materials to overcome the electrochemical corrosion of conventional carbon materials.Titanium carbide,due to a better conductivity and a large specific surface area,high oxidation resistance and corrosion resistance,has become into a very popular catalyst support.The dispersibility and stability of the catalyst on non-carbon-based supports are an important issue.In this paper,the surface modification of titanium carbide was carried out.As a new catalyst support for Pd-catalyzed formic acid oxidation,the catalytic performance of the developed catalyst for oxidation of formic acid was studied.(1)The Pd/TiC catalyst was prepared through impregnation reduction at TiC support.The structure,component and morphology of the catalysts were characterized.The electrocatalytic oxidation of formic acid at Pd/TiC catalyst was researched by electrochemical method.The results showed that Pd nano-particles had smaller average sizes and better dispersibility on the surface of titanium carbide than on carbon black.Pd/TiC catalyst owned higher catalytic activity,stability and anti-CO poisoning ability for oxidation of formic acid.It was mainly attributed to the interaction between Pd and TiC as well as the formation of oxygen-containing substances on the TiC surface.(2)TiC was modified by acidification and using cationic polymer PDDA and Pd/AO-TiC and Pd/TiC(P)catalysts were prepared.The microstructures and structures of the catalysts were characterized by transmission electron microscopy(TEM)and X-ray diffraction(XRD).The electrocatalytic activity of two catalysts for formic acid was investigated by a series of electrochemical tests.The results of TEM showed that the activated TiC via acidification and adding cationic polymer increased the active sites on the surface of TiC.Pd could be well deposit on the support surface after treatment.The catalysts of Pd/AO-TiC and Pd/TiC(P)owned better activity for the oxidation of formic acid than Pd/TiC catalyst.Pd/TiC(P)catalyst demonstrated the optimum anti-CO poisoning ability and stability.(3)The Pd-Ru/TiC(P)catalysts with different atomic ratios were synthesized by electrostatic self-assembly and in situ reduction.The morphologies and structures of the catalysts were characterized by XRD,TEM and EDS.And the electrocatalytic oxidation of formic acid was tested by a series of electrochemical methods.The results showed that the addition of Ru could micrify the particle size of the catalyst.A good alloy structure was formed between Ru and Pd.Pd-Ru/TiC(P)possessed better catalytic activity and stability than Pd/TiC(P)catalyst,while Pd3Ru1/TiC(P)exhibited the strongest catalytic stability and activity.This fact could be attributed to the bifunctional mechanism.Ru was easy to activate the water at low potential to form Ru-OHad,which would be conducive to the oxidation of intermediate products of CO to release the active site of Pd and maintain the catalytic performance of the catalyst.