Study On Preparation Of Pt/C And Pt-Cr/C Catalysts By Inorganic Colloid Method

Proton exchange membrane fuel cell (PEMFC) has a great potential to be commercialized for portable and automobile application. As a kind of key materials of PEMFC, Pt/C catalysts is widely used nowadays, but considering the limitation and high cost of the metal Pt resources, a large amount of work has been devoted to enhance the performance and to lower cost of PEMFC, such as the study of high performance Pt/C and Pt-M/C catalysts.In this paper, supported Pt/C catalysts used in proton exchange membrane fuel cells (PEMFC) were prepared by the inorganic colloid method. We investigated the influences of pH value, concentration and temperature of solutions on the formation and stability of the PtO2 colloid. The performances of Pt/C catalysts prepared with different concentrations of HCHO reducing agents were analyzed. Besides, we also studied the influences of Vulcan XC-72 carbon pretreatment and the heat treatment of catalyst on the performance of Pt/C catalysts. In the other hand, the ineffective Pt/C catalysts were reprocessed in order to reuse in proton exchange membrane fuel cell (PEMFC). Pt residues were obtained by heat-treatment of ineffective Pt/C catalysts at a higher temperature in air, and then were dissolved by a suitable amount of aqua regia. The solution was boiled, concentrated and diluted again to form the H2PtCl6 solution with a suitable concentration. Pt/C catalysts were prepared with the H2PtCl6 solution by the inorganic colloid method. Transmission electron microscopy(TEM)results showed that the Pt/C catalysts with 3nm platinum crystallites, a very narrow size distribution and a higher dispersion was achieved at optimal preparation conditions. The measurement results of I~E characteristics of a single PEMFC and cyclic voltammetry (CV) of Pt/C catalyst indicated that the Pt/C catalysts prepared in this work exhibited better electrochemical performance.Based on the inorganic colloid method, we researched the synchronous and distributed reduced methods of Pt-Cr/C catalysts used in oxygen reduction reaction(ORR). XRD analysis showed that in the prepared Pt-Cr/C catalysts, the relative content of the Pt (100) crystal face was increased and Pt-Pt nearest distance was reduced, which benefits the acceleration of the oxygen reduction reaction in PEMFC. Cyclic voltammetry (CV) analysis of Pt-Cr/C catalysts showed that the electrocatalytic activity for ORR appeared better than that of Pt/C catalysts.