Effects of TiO₂ in Pd-TiO₂/C for glycerol oxidation in a direct alkaline fuel cell

The Pd-TiO₂ electrocatalysts were synthesized via sodium borohydride reduction and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry, chronoamperometry and attenuated total reflectance-Fourier transform infrared (ATR-FTIR). The X-ray diffraction experiments of the Pd-TiO₂ showed peaks associated with Pd face-centered cubic (fcc) structure and peaks characteristics of TiO₂ (anatase phase) with a tetragonal structure. The TEM images showed that the Pd and TiO₂ nanoparticles were well distributed in the carbon support showing some clustered regions with nanoparticle sizes between 7 and 8 nm. Cyclic voltammograms showed an increase in current density values after the glycerol adsorption process. Experiments in alkaline direct glycerol fuel cells at 60 °C showed a higher power density for Pd-TiO₂/C (70∶30) in comparison to the commercial Pd/C electrocatalyst indicating that the use of the TiO₂ co-catalyst with Pd nanoparticles had a beneficial behavior. This effect can be attributed to the electronic effect or to the bifunctional mechanism. Molecules with high-value added glyceraldehyde, hydroxypyruvate and formate were identified as electrochemical reaction products of glycerol on all prepared electrocatalysts.