LAUSR

Abstract Ti1-xMoxO2–active carbon composites are promising new supports for Pt-based fuel cell electrocatalysts, which provide enhanced stability and excellent CO tolerance. The catalytic properties of the system are mainly determined by the interactions between Mo and Pt. The aim of this work is to explore the nature of these interactions by comparing the response of Mo/Pt model systems and real Pt/Ti0.8Mo0.2O2–active carbon composite supported catalysts on annealing/reductive treatments using photoelectron spectroscopy. According to our observations, a Mo-Pt surface alloy is formed upon annealing the Mo/Pt model system in vacuum at 300 °C or reduction in hydrogen at 100 °C. A peculiar feature of this alloy is the considerable stability of the metallic state of Mo against oxidation. The formation of this alloy upon annealing can be used as an indicator of the Pt-bound state of the catalytically active Mo species in the system. As in the case of the mixed oxide composite supported catalysts the stable metallic Mo state was not achieved, the results suggest that the catalytically important Mo species are not directly attached to the surface of the Pt particles, instead, they perform their co-catalytic role in a support-bound state.