Preparation of Pt electrocatalyst supported by novel, Ti (1−x) Mo x O 2 -C type of composites containing multi-layer graphene

Ball milling is a relative simple and promising technique for preparation of inorganic oxide–carbon type of composites. Novel TiO 2 -C and Ti 0.8 Mo 2 O 2 -C type of composites containing multi-layer graphene were prepared by ball milling of graphite in order to get electrocatalyst supports for polymer electrolyte membrane fuel cells. Starting rutile TiO 2 was obtained from P25 by heat treatment. Carbon-free Ti 0.8 Mo 2 O 2 mixed oxide, prepared using our previously developed multistep sol–gel method, does not meet the requirements for materials of electrocatalyst support, therefore parent composites with Ti 0.8 Mo 2 O 2 /C = 75/25, 90/10 and 95/5 mass ratio were prepared using Black Pearls 2000. XRD study of parent composites proved that the oxide part existed in rutile phase which is prerequisite of the incorporation of oxophilic metals providing CO tolerance for the electrocatalyst. Ball milling of TiO 2 or parent composites with graphite resulted in catalyst supports with enhanced carbon content and with appropriate specific surface areas. XRD and Raman spectroscopic measurements indicated the changes of graphite during the ball milling procedure while the oxide part remained intact. TEM images proved that platinum existed in the form of highly dispersed nanoparticles on the surface of both the Mo-free and of Mo-containing electrocatalyst. Electrocatalytic performance of the catalysts loaded with 20 wt% Pt was studied by cyclic voltammetry, CO ads -stripping voltammetry done before and after the 500-cycle stability test, as well as by the long-term stability test involving 10,000 polarization cycles. Enhanced CO tolerance and slightly lower stability comparing to Pt/TiO 2 -C was demonstrated for Pt/Ti 0.8 Mo 2 O 2 -C catalysts.