Electrocatalytic Activity of Carbon Nanotube-Supported Pt-Based Bimetallic Catalysts for Borohydride Electro-Oxidation

Over the past ten years, sodium borohydride (NaBH₄) has drawn attention due to the great usage of NaBH₄ in energy systems. It can be directly oxidized in a direct borohydride fuel cell (DBFC) or it can produce hydrogen on demand. In this study, catalysts of Pt and PtAu supported on carbon nanotubes (CNT) were prepared using a NaBH₄ reduction process to explore the electro-oxidation of NaBH₄. The characterization of the catalysts has been performed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The produced catalysts were about 4 nm in size and shared a similar particle shape. Cyclic voltammetry, linear sweep voltammetry, chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements were evaluated for borohydride electro-oxidation. The experimental conditions were optimized by cyclic voltammetry for BH₄⁻ electro-oxidation on PtAu (70:30)/CNT. The EIS and CA results were in a good agreement with the cyclic voltammetry results in terms of electrocatalytic activity and stability of the PtAu/CNT, Au/CNT, and Pt/CNT catalysts. The improved performance of BH₄⁻ electro-oxidation can be ascribed to the complementary actions of CNT-supported Pt and Au particles, which improve catalyst contact and usage. These findings imply that the PtAu (70:30)/CNT catalyst is a viable anode catalyst for use in direct borohydride fuel cells.