The Synthesis of Metallic β-Sn Nanostructures for Use as a Novel Pt Catalyst Support and Evaluation of Their Activity Toward Methanol Electrooxidation

This study offers a unique insight into the use of high surface area metallic tin as support material for platinum catalysts for fuel cell application. We have synthesized high surface area metallic β-tin nanostructures (TNSs) in aqueous solutions by novel one-pot process and used it as a platinum catalyst support in methanol electrooxidation reaction. Rigorous study of parameters controlling the size and shape of TNSs was performed, including selected surfactant molecules at various concentrations, tin salts, and the addition of sodium citrate. Rod-shaped particles with a 50-nm diameter and 500-nm length were obtained from solutions of selected surfactant in concentrations of 1–20 mM by sodium borohydride reduction. These particles had a β-Sn crystalline core with a main lattice plane of (101) and were covered by a 4-nm oxide shell. A maximal surface area of 170 m² g⁻¹ was measured from a sample prepared by using low concentration of sodium dodecyl sulfate (SDS) (1 mM). This sample is composed of nanorods and nano semi-spherical shape tin particles. Addition of sodium citrate, which acts as a Sn²⁺ ion ligand, yields longer rods. Electrochemical oxidation of methanol on platinum catalyst, supported on metallic Sn nanostructure, exhibits a high activity, which is comparable to commercial carbon-supported platinum catalysts. In situ surface-enhanced Raman (SER), emphasizing the role of surface oxides on the methanol oxidation activity, further studied methanol oxidation on Pt/TNS, Pt/C, and Pt-Sn alloy catalyst.