Pt nanoparticles deposited on TiO sub(2) based nanofibers: Electrochemical stability and oxygen reduction activity

The electrochemical stability of Pt deposited on TiO sub(2) based nanofibers was compared with commercially available carbon supported Pt. Prior to the Pt deposition the TiO sub(2) material, which was either undoped or Nb doped, was air calcined. In one case the undoped TiO sub(2) was also reduced in a hydrogen atmosphere. XRD analysis revealed that the unreduced TiO sub(2) was present in the anatase phase, irrespective of whether the Nb dopant was present, whereas the rutile phase was formed due to reduction with H sub(2). The diameter of the TiO sub(2) fibers varied from 50 to 100 nm, and the average Pt particle diameter was approximately 5 nm. Pt supported on TiO sub(2) was more stable than Pt supported on C when subjected to 1000 voltammetric cycles in the range of 0.05-1.3 V vs. RHE. Nb doped TiO sub(2) showed the highest stability, retaining 60% of the electrochemically active surface area after 1000 cycles compared to the state after 100 cycles, whereas the carbon supported catalyst retained 20% of the active surface area. The commercial catalyst had the highest oxygen reduction activity due to its larger specific area (17.1 m super(2) g super(-1) vs. 5.0 m super(2) g super(-1) for Pt/TiO sub(2)-Nb, measured after 100 cycles) and the higher support conductivity. The Pt supported on Nb doped or on H sub(2) reduced TiO sub(2) was more active than Pt supported on air calcined and otherwise unmodified TiO sub(2).