Novel Pt Electrocatalysts: Multifunctional Composite Supports for Enhanced Corrosion Resistance and Improved CO Tolerance

The electrochemical peculiarities of novel 20 wt% Pt electrocatalysts supported on Ti_0.6Mo_0.4O₂–C composite materials in low-potential CO oxidation reaction (LPCOR) were investigated. The oxidation of CO on the Mo-containing Pt-based catalyst commences at exceptionally low potential values (ca. 100 mV). The results suggest that only CO adsorbed on specific Pt sites, where Pt and Mo atoms are in atomic closeness, can be oxidised below 400 mV potential. When the weakly bounded CO is oxidized, some hydrogen adsorption can take place on the released surface, although this amount is much smaller than in the case of a CO-free Pt surface. The Pt/Ti_0.6Mo_0.4O₂–C catalyst loses its activity in LPCOR when Mo becomes oxidized (above ca. 400 mV). Accordingly, presence of Mo species in lower oxidation state than 6+ is supposed to have crucial role in CO oxidation. Nevertheless, re-reduction of oxidized Mo species formed above 400 mV is strongly hindered when adsorbed CO species are still present. Note that CO_ads species can be completely removed only above 550 mV. Oxidized Mo species can be re-reduced and the activity in the LPCOR can be restored if the platinum surface is CO-free. Clear correlation between the so-called “pre-peak”, the molybdenum redox phenomenon and the CO tolerance of the 20 wt% Pt/Ti_0.6Mo_0.4O₂–C system was established. Better performance of the Pt/Ti_0.6Mo_0.4O₂–C electrocatalyst compared to commercially available reference Pt/C and state-of-art CO-tolerant PtRu/C (Quintech) catalysts was also demonstrated.