Synthesis and evaluation of carbon nanotube-supported RuSe catalyst for direct methanol fuel cell cathode

Ruthenium selenide (RuSe) supported on a carbon nanotube (CNT) material, i.e., RuSe/CNT, with a controlled composition (Ru:Se = 1:0.2) was synthesized using a modified polyol method as a model catalyst for direct methanol fuel cell (DMFC) cathode. The prepared electrocatalyst was physically characterized by means of Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) Spectroscopy and X-ray Photoelectron Spectroscopy (XPS), and its activity for oxygen reduction reaction (ORR) was examined using Linear-Sweep Voltammetry (LSV). In addition, the methanol tolerance was characterized using Electrochemical Impedance Spectroscopy (EIS). It was found that the prepared RuSe/CNT catalyst has good catalyst morphology, uniform and small particle size, and controllable catalyst composition. After subjecting to a proper heat treatment at 400 °C, the electrocatalyst exhibits a good oxygen reduction activity with high methanol tolerance. From both LSV and XPS analyses, it was concluded that a high Se3d5/2 content plays an important role for oxygen reduction on RuSe/CNT. The EIS characterization also identified the presence of reaction intermediates during the oxygen reduction process. Based on the test results, the mechanisms underlying the dual function of the RuSe/CNT catalyst are proposed. The prepared catalyst was further evaluated for its potential application to DMFC. At 70 °C, the single-cell DMFC integrated with RuSe/CNT exhibited a performance much better than that incorporated with Pt/C counterpart when operated with a high-concentration (i.e., 6 M) methanol fuel. However, substantial improvements are still needed for practical applications.