Platinum Supported On Metallic Compound/Nanodiamond

Direct methanol fuel cells(DMFCs) have been researched widely and considered to be promising candidates for a range of mobile applications owing to their low operating temperatures, high energy density and environmental friendliness. The working efficiency and life of DMFCs are essentially governed by the elcctrocatalytic activity and stability of electrocatalyst. Pt/C electrocatalyst is usually used as a commercial electrocatalyst, however, there are some issues such as the oxidation of carbon black support, migration and aggregation of Pt nanoparticles(NPs). These could result in catalyst’s deactivation, thus reduce the efficiency of DMFCs.On the issue of catalyst deactivation caused by carbon black’s oxidation and Pt NPs’ aggregation, sp3 nanodiamond(ND) possessing high thermal stability and chemical stability was employed as the primary support, which was midified by various metallic compund layer. The ND core possessed excellent stability, at the same time, there was a strong metal-support interaction between metallic compound and Pt NPs to anchor Pt NPs. Therefore, Pt NPs supported on metallic compound/ND would be very promising electrocatalysts possessed high catalytic activity and excellent durability.1) Nano titania modified nanodiamond(Ti O2/ND) was prepared by a microwave hydrolysis method, and then platinum nanoparticles(NPs) were deposited on the Ti O2/ND support using a microwave-assisted polyol method. The electrochemical results showed that the Pt/Ti O2/ND catalyst possessed much higher electrocatalytic activity for methanol oxidation reaction(MOR) compared with Pt NPs supported on ND(Pt/ND) in acid medium. A high stability of Pt/Ti O2/ND catalyst was ascribed to an anchoring effect of the Ti O2 layer and a high stability of the Ti O2/ND support in acid solution.2) To further enhance the conductivity of Ti O2/ND support, ND was treated in a vacuum at temperature of 1300 °C for 2 h to prepare graphitized ND(GND), followed by the deposition of Ti O2 and Pt on the surface of GND to obtain Pt NPs supported on Ti O2 modified GND(Pt/Ti O2/GND). Pt/C and Pt supported on Ti O2/C(Pt/Ti O2/C) catalysts were obtained for comparison. The Pt/Ti O2/GND showed excellent electrocatalytic activity for MOR and oxygen reduction reaction(ORR). In addition, the Pt/Ti O2/GND catalyst demonstrated a better durability than the other two catalysts due to the higher stability of Ti O2/GND support and the anchoring effect of the Ti O2 layer to Pt NPs.3) A novel core-shell support material was designed with ND as core possessed excellent stability and Ti N as shell improved the conductivity of support. The nano-Ti N shell was decorated on the surface of ND by annealing Ti O2 in nitrogen atmosphere, and the obtained Ti N/ND was employed to support Pt NPs. TEM results showed ND particles were coated uniformly by the Ti N layer possessed rough surface because the mild transformation condition from Ti O2 to Ti N made the granular morphology of Ti O2 NPs remain. The Ti N/ND support possessed a much more stability than the carbon black and exhibited a bigger background current density than the ND. The Pt/Ti N/ND catalyst showed higher catalytic activity and better stability for MOR and ORR compared with the Pt/C and Pt/ND.4) An epitaxial Ti C/ND was fabricated by a simple one-pot synthesis method and used to support Pt NPs to obtain Pt/Ti C/ND catalyst. An epitaxial WC layer was prepared on the surface of ND using microwave heating polyol methaod and hydrogen reduction, followed by the deposition of Pt NPs to obtain Pt/WC/ND catalyst. The Pt/Ti C/ND and Pt/WC/ND exhibited much higher catalytic activity and stability in MOR and ORR than the Pt/ND catalyst. In addition, the electrochemical stabilities of the Pt/Ti C/ND and Pt/WC/ND were more outstanding compared with the Pt/C. The superior durability can be attributed to the chemical stability of ND core and the anchoring effect of the carbides layer to Pt NPs.