Effects of synthesis condition on formation of desired crystal structures of doped-TiO2/carbon composite supports for ORR electrocatalysts

The composite supports, (Nb0.07Ti0.93O2)25wt%–C75wt% and (Nb0.07Ti0.93O2)70wt%–C30wt%, as well as their supported Pt–Pd alloy electrocatalysts, 20 wt%Pt0.62Pd0.38/((Nb0.07Ti0.93O2)25wt%–C75wt%)80wt% and 20 wt%Pt0.62Pd0.38/((Nb0.07Ti0.93O2)70wt%–C30wt%)80wt% for oxygen reduction reaction (ORR), are synthesized, respectively, using an acid-water based solution as solvent. The effects of three factors, namely concentration of HCl, the ratio of titanium precursor to solvent, and the ratio of metal-oxide to carbon in the composite support, on the TiO2 anatase-to-rutile transition are investigated in an effort to optimize the supports and their supported catalysts with respect to both ORR catalytic activity and durability. Based on both the high ORR activity and durability, these catalysts should be feasible if used in PEM fuel cells as cathode electrocatalysts.