Preparation Of TiO₂/C Supported Platinum Catalysts And Their Catalytic Activity For Oxygen Reduction Reaction

Recently,carbon supported platinum or platinum based alloy for the cathodic ORR are the best catalysts. However, several issues still exist with Pt based catalyst including prohibitive cost, carbon-support corrosion, and methanol poisoning, which hinder its commercial application. To address this problem, many efforts have been made to develop high stability of cathode catalyst carrier for fuel cell applications. Among these materials, TiO2 act as a carrier or cocatalyst for potential application of ORR due to its high chemical stability.First we prepared TiO2/C carrier materials with different loading methods and systematic investigated the effect of temperature, Pt content, Pt reduction methods and pH value on catalytic activity using linear sweep voltammetry(LSV). These results indicate that TiO2/C(TiO2 in situ growing on the C support) after 2 h heat treatment at 550 °C supported 20% Pt through photo reduction shows good performance compare to Pt/C.The structure and composition of Pt/TiO2/C composites was characterized by TEM, XRD, TG-DTA, XRF and XPS analysis. These results indicate that most of the Pt particles were dispersed uniformly on the anatase TiO2 and calculated mean size is 3~4 nm. TiO2 did not affect the catalytic activity of the catalysts, mainly because some C doped in TiO2 increase conductive property. The Chronoamperometry(CA) test shows that material has stable performance and high methanol tolerance ability compared to commercial Pt/C. Furthermore, the Reaction kinetics results indicate that electron transfer number of Pt/TiO2/C for ORR is 4, which is similar to Pt/C.Secondly, we used TiO2 as a predominant component for C-based ORR catalyst and fiber-like polyaniline(PANI) introduced as a C-N precursor and also acts as a good template for growing TiO2 crystals by hydrothermal synthesis. Then we investigated systematically the catalytic effects of different acid and alkali to the surface treatment and different proportion of Pt. The characterization results show that the carbonization of PANI, rod-like TiO2 turn to be rutile phase, N doped in the C framework during 800 ? heat treatment. The CA test suggest the stability of Pt/TiO2/C-N is higher than Pt/C. Meanwhile, The Reaction kinetics results indicate that electron transfer number of Pt/TiO2/C-N for ORR is 4, which is similar to Pt/C.The significantly enhanced stability is probably ascribed to the following two reasons:(1) the excellent inherent chemical stability of TiO2;(2) the strong interactions of ?TiO2-PANI coupling? and ?metal-support coupling?. Thus, TiO2/C appears a promising substitute for C materials when supporting metal catalyst for PEMFC application in terms of electrochemical stability.