The Effect of TiO2 on the Catalytic Activity of a PtRu/C Catalyst for Methanol Oxidation

In this work, the effect of the addition of different amounts of TiO2 nanotubes to a PtRu catalyst supported on Vulcan XC-72R carbon black for methanol oxidation was studied. Two approaches were used for the catalyst preparation. In the first case, Pt and Ru metal ions were impregnated onto the support (C-TiO2) and subsequently reduced with NaBH4. In the second case, the metal ions were first reduced and then impregnated, in order to obtain a catalyst with metal loading of 30 % of PtRu (50:50 at.% composition of Pt/Ru) and varying concentrations of TiO2 (5-15 wt%); the actual composition was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. The electrochemical properties were studied via cyclic voltammetry and chronoamperometry in 0.5 M H2SO4 solution. X-ray diffraction analyses indicated the formation of PtRu alloy with different degrees of alloying. The CO-stripping voltammetry studies showed that both the onset potential and the peak potential are dependent on the catalyst composition; the PtRu/C-TiO2(10) exhibited a relatively higher CO oxidation current compared to those exhibited by the other catalysts. Both the linear sweep voltammetry and the chronoamperometric results also demonstrated that the PtRu/C-TiO2(10) catalyst exhibited a higher methanol oxidation current and a lower poisoning rate among the investigated catalysts with various TiO2 nanotube contents (i.e., 0, 5, and 15 % TiO2). The prepared catalysts revealed essentially the same catalytic performance independently of the procedure used for their preparation.