Enhanced activity, durability and anti-poisoning property of Pt/W18O49 for methanol oxidation with a sub-stoichiometric tungsten oxide W18O49 support

Abstract

In this work, sub-stoichiometric tungsten oxide W₁₈O₄₉ was first studied as a support for a Pt catalyst. Metallic monoclinic W₁₈O₄₉ nanorods (NRs) with an isotropic morphology can not only improve electron, reactant, and product transport but can also enhance the utilisation of Pt for the methanol oxidation reaction (MOR). The specific activity for the forward peak (I_f) of Pt/W₁₈O₄₉ was determined to be 1.14 mA cm_Pt⁻², which is approximately 1.4 and 1.8 times higher than that of Pt-black and Pt/C, respectively. On the other hand, the robust W₁₈O₄₉ NRs improve the stability of Pt/W₁₈O₄₉. After a 5000-cycle accelerated durability test, the electrochemical surface area (ECSA) loss rate of Pt/W₁₈O₄₉ was only 27.12%, less than that of Pt-black and Pt/C. Moreover, numerous oxygen vacancies and two valence states of W (W⁵⁺ and W⁶⁺) were found to co-exist in W₁₈O₄₉, which may promote hydrogen spillover and oxygen buffering. These effects together contributed to improve the anti-poisoning properties of Pt/W₁₈O₄₉ towards the intermediates in the MOR. The peak current ratio of the forward versus the backward (I_f/I_b) reaction is 1.12 for Pt/W₁₈O₄₉, 0.99 for Pt-black, and 0.79 for Pt/C. It was found that the Magnéli phase W₁₈O₄₉ may be a promising catalyst support for use in the MOR.