Effect of the reductive treatment on the state and electrocatalytic behavior of Pt in catalysts supported on Ti 0.8 Mo 0.2 O 2 -C composite

Ti (1-x) Mo x O 2 -carbon composites are promising new supports for Pt-based electrocatalysts in polymer electrolyte membrane fuel cells offering exciting catalytic properties and enhanced stability against electrocorrosion. Pt and the mixed oxide form a couple liable for strong metal-support interaction (SMSI) phenomenon, generally manifesting itself in decoration of the metal particles by ultrathin layers of the support material upon annealing under reductive conditions. The aim of this work is to evaluate the SMSI phenomenon as a potential strategy for tailoring the properties of the electrocatalyst. A 20 wt% Pt/50 wt% Ti 0.8 Mo 0.2 O 2 -50 wt% C electrocatalyst prepared on Black Pearls 2000 carbon functionalized with HNO 3 and glucose was reduced at 250 °C in H 2 in order to induce SMSI. The electrocatalytic properties and the stability of the reduced and the original catalysts were analyzed by cyclic voltammetry and CO ads stripping voltammetry. Structural investigations as well as X-ray photoelectron spectroscopy (XPS) measurements were performed in order to obtain information about the details of the interaction between the oxide and the Pt particles. The electrochemical experiments pointed out a small loss of the electrochemically active surface area of Pt in the reduced catalyst along with enhanced stability with respect to the original one, while structural studies suggested only a minimal decrease of the Pt dispersion. At the same time, hydrogen exposure experiments combined with XPS demonstrated the presence of Mo species directly adsorbed on the Pt surface. Thus, the properties of the reduced catalyst can be traced to decoration of the surface of Pt by Mo-containing species.