Improved electrocatalytic activity of Pt supported onto Fe-doped TiO2 toward ethanol oxidation in acid media

Abstract

The low stability of Pt-based catalysts due to severe corrosion of carbon support is one of the most critical technical issues hindering the widespread application of proton exchange membrane fuel cells. Here, we report the successful deposition of Pt nanoparticles on both pure titanium dioxide (TiO2) and Fe-doped TiO2 powder by chemical reduction using formic acid and their performance toward ethanol oxidation in acid media. First, the supported TiO2 was synthesized by the sol–gel method, and its physical-chemical properties were modified by the incorporation of iron (5.0 and 10.0 wt% Fe) into the structure of TiO2. The supports and catalysts were characterized by photoacoustic spectroscopy (PAS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The PAS data show that the doping of TiO2 with iron ions (III) decreases the band gap from 2.95 eV (undoped TiO2) to lower values depending on the iron content in the support (1.97 eV and 1.90 eV for 5Fe–TiO2 and 10Fe–TiO2, respectively). The XRD and TEM results indicate the presence of small-sized (around 3.5 nm) Pt nanostructures deposited onto the supports. The XPS analyses reveal surfaces rich in metallic Pt and oxygen species (O2− species, OH− and O atoms) in the vicinity of oxygen vacancies, as well as strong interactions between Pt nanoparticles and the Fe–TiO2 support. The Pt/Fe–TiO2 electrocatalyst exhibits higher catalytic activity toward ethanol oxidation than Pt/TiO2 and commercial Pt/C electrocatalysts (used as reference). The efficiency of Pt utilization increases with the Fe content. The sample with 10 wt% (mol/mol) of iron is then the most active catalyst. The enhanced activity and stability of the Pt/Fe–TiO2 catalyst can be attributed to the synergic and electronic effect of the compounds, Pt, and Fe–TiO2.