WO₃-N-doped Carbon Supported PtSn Nanoparticles for Improved Ethanol Oxidation

Abstract

A new nitrogen-doped carbon support for Pt-based electrocatalysts was prepared by carbonizing polypyrrole formed on the surface of WO 3 nanoparticles (WO 3 -CN x ). Morphologies of WO 3 -CN x and PtSn/WO 3 -CN x were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. PtSn nanoparticles were well-dispersed on the surface of WO 3 -CN x . Electrocatalytic results showed that PtSn/WO 3 -CN x is more active than PtSn/C in the ethanol oxidation reaction (EOR), since smaller PtSn nanoparticles were grown on the surface of WO 3 -CN x and highly electrically conductive WO 3 -CN x facilitated the electron transport occurred during the EOR. PtSn/WO 3 -CN x also exhibited better durability and higher stability in ethanol oxidation reaction than PtSn/C. These results indicated that WO 3 -CN x has potential to be used as a catalytic support with high-performance for Pt-based electrocatalysts used in fuel cells.PtSn nanoparticles deposited on carbon support are the most promising catalyst for the ethanol oxidation reaction among various Pt-based binary catalysts. 1 In order to further improve PtSn/C catalytic activity toward EOR, the efforts are currently focus on the effect of synthesis methods on the composition and structure of PtSn/C which have a huge impact on EOR catalytic activity. 2-6 Currently, carbon black is widely used as catalyst support material for Pt-based electrocatalysts. 7 However, the corrosion of carbon under the fuel cell operating conditions has been identified to be the major contributor to the low catalyst performance, durability and reliability, 8 which is one of the major barriers to the wide application of Pt-based electrocatalysts. The support for Pt-based electrocatalyst is of equal importance as the active material nanoparticles for the catalytic performance and stability of the catalyst. 8 Therefore, there is an urgent demand for developing alternative support with much better durability and stability. For the new alternatives, some requirements should be met, such as high surface area, high dispersion of catalytic metals and high corrosion resistance under the harsh fuel cell operating conditions. With regard to the development of alternative to conventional carbon support for fuel cell catalysts, a lot of work has been done in the past decades. The alternative support materials, including metal support, nitride, carbide, mesoporous silicas, metal oxides and conducting polymers have been widely investigated to solve the corrosion issue, which is suffered by the traditional carbon supports. 7 Among these alternative support materials, metal oxides are considered to be promising support materials using in electrocatalysts for fuel cell. Various metal oxides, such as V 2 O 5 , 9 WO x , 10 were developed as supports to enhance the stability and performance of Pt-based electrocatalysts. Among these oxides, WO 3 is considered as a potential non-carbon catalyst support for Pt and PtRu and the obtained Pt/WO 3 catalysts showed very high catalytic activi...