An ambient aqueous synthesis for highly dispersed and active Pd/C catalyst for formic acid electro-oxidation

摘要

An experimentally simple process is reported in aqueous solution and under ambient conditions to prepare highly dispersed and active Pd/C catalyst without the use of a stabilizing agent. The [Pd(NH_3)_4]~(2+) ion is synthesized with gentle heating in aqueous ammonia solution without formation of Pd(OH)_x complex intermediates. The adsorbed [Pd(NH_3)_4]~(2+) on the surface of carbon (Vulcan XC-72) is reduced in situ to Pd nanoparticles by NaBH_4. The Pd/C catalyst obtained is characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that highly dispersed Pd/C catalyst with 20wt.% Pd content and with an average Pd nanoparticle diameter of 4.3-4.7 nm could be obtained. The electrochemical measurements show that the Pd/C catalyst without stabilizer has a higher electro-oxidation activity for formic acid compared to that of a Pd/C catalyst prepared in a traditional high temperature polyol process in ethylene glycol.