Application Of TiO₂ Nanomaterials In Anode Catalysts Of Direct Alcohol Fuel Cells

TiO₂ has attracted more and more attention in photocatalysis due to its non-toxity, low-price and high catalytic effect. Recently, applications of TiO₂ in fuel cells have been reported. A series of TiO₂ and titanate nanomaterials were synthesized and used as co-catalysts in anode catalysts of direct alcohol fuel cells (DAFC).The alcohol oxidation performance and mechanism of the samples were studied. TiO₂ nanomaterials were also used as catalyst supports to synthesize Pt/TiO₂ catalysts and the electro-chemical properties of Pt/TiO₂ were studied by introducing UV light into the system.Using various nanoparticles as raw materials, titanate nanotubes were synthesized by hydrothermal method. Their co-catalytic effects were studied by structure analysis, impedance tests and electro-chemical measurements. The results show that titanate nanotubes could accelerate the methanol and ethanol oxidation on Pt/C catalyst, and the methanol oxidation current increased more significantly. The co-catalytic effects of titanate nanotubes were influenced by: the adsorbed water and structure water content, the production yield of nanotubes and the proton conductivity.One-dimension TiO₂ and titanate nanomaterials with various morphologies were synthesized using commercial anatase TiO₂ nanoparticles as raw materials. The co-catalytic effects and mechanism were studied by physically mixing these nanomaterials with Pt/C. These one-dimension TiO₂ and titanate nanomaterials could increase the methanol oxidation current on Pt/C. The influences of surface area, porous structure, adsorbed water and structure water content, crystal structure and proton conductivity of these nanomaterials on co-catalytic effect have been studied. Co-catalysts which have good contact with Pt nanoparticles, with proper porous structure and high proton conductivity could accelerate the methanol oxidation. Co-catalysts containing more water have better performance in oxidizing intermediate and CO tolerance. TiO₂ (B) nanobelts with special crystal structure and morphology have good co-catalytic effect due to the proton easily transport along the long-axis.Pt/TiO₂ catalysts were synthesized by using different TiO₂ nanomaterials as catalyst supports by glycol reflux method. The methanol oxidation properties and mechanisms of these catalysts have been studied. TiO₂ supports with gas diffusion channels, higher proton conductivity and more water content could accelerate the methanol oxidation activity of Pt/TiO₂. The influence of TiO₂ supports were investigated combining with photochemical measurements. The CO tolerance and methanol oxidation peaks of Pt/TiO₂ catalysts increased significantly under UV illumination. The electrochemical activities of catalysts were much improved when the TiO₂ supports have better photocatalytic activities. For methanol oxidation tests, considerable current also appeared on bare TiO₂ supports when they were under UV illumination, but the current density is much smaller than that on Pt/TiO₂ catalysts.