PdRu/C catalysts for ethanol oxidation in anion-exchange membrane direct ethanol fuel cells

摘要

Carbon supported PdRu catalysts with various Pd:Ru atomic ratios were synthesized by impregnation method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electrochemical half-cell tests, and the anion-exchange membrane direct ethanol fuel cell (AEM-DEFC) tests. XRD results suggest that the PdRu metal exists on carbon support in an alloy form. TEM study shows that the bimetallic PdRu/C catalysts have slightly smaller average particle size than the single metal Pd/C catalyst. Lower onset potential and peak potential and much higher steady state current for ethanol oxidation in alkaline media were observed on the bimetallic catalysts (Pd_xRu_y/C) than on the Pd/C, while the activity for ethanol oxidation on the pure Ru/C was not noticeable. By using Pd/C anode catalysts and MnO_2 cathode catalysts, AEM-DEFCs free from the expensive Pt catalyst were assembled. The AEM DEFC using the bimetallic Pd_3Ru/C anode catalyst showed a peak power density as high as 176 mW cm~(-2) at 80 ℃, about 1.8 times higher than that using the single metal Pd/C catalyst. The role of Ru for enhancing the EOR activity of Pd/C catalysts is discussed.