Tungsten nitride decorated CNTs as efficient hybrid supports for PtRh alloys in electrocatalytic ethanol oxidation

Abstract

Direct ethanol fuel cells (DEFCs) offer an attractive alternative to fossil fuel-powered devices due to their high energy density and environmental benignity. However, high cost and poor stability of catalysts are still the main obstacles for the commercialization of DEFCs. Herein, a novel catalyst comprising PtRh alloys anchored on carbon nanotubes that decorated with tungsten nitride (Pt9Rh-WN/CNTs) was synthesized via impregnation-reduction method and followed by thermal annealing in N2. The X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and transmission electron microscopy (TEM) are employed to characterize the corresponding physico-chemical properties of the as-prepared catalysts. Electrocatalytic performance for ethanol oxidation is evaluated by cyclic voltammetry, linear scan voltammetry, CO-stripping voltammograms, chronoamperometry and chronopotentiometry. The current density on Pt9Rh-WN/CNTs is 484.8 mA mgPt−1, which is much higher than that of Pt9Rh/CNTs (305.7 mA mgPt−1) and Pt/CNTs (135.1 mA mgPt−1). Most importantly, the onset potential for CO oxidation on Pt9Rh-WN/CNTs is 0.27 V, which is more negative than that on Pt9Rh/CNTs (0.37 V) and Pt/CNTs (0.40 V). Therefore, the Pt9Rh-WN/CNTs catalyst displays both outstanding catalytic activity and excellent CO-poisoning tolerance for ethanol oxidation. Synergistic effects arising between WN and PtRh alloy along with nitrogen-doping effects of CNTs with ammonia are proposed to contribute to the outstanding performance of this catalyst in ethanol oxidation.