Multiwalled Carbon Nanotubes Composited with Palladium Nanocatalysts for Highly Efficient Ethanol Oxidation

Carboxyl multi-walled carbon nanotubes (MWNTs-COOH) decorated with different palladium (Pd) nanoparticle loadings were synthesized by thermally decomposing different amounts of palladium acetylacetonate (Pd(acac)(2)) in a refluxing xylene solution with a fixed amount of dispersed MWNTs-COOH. The increased ratio of D band/G band and the decreased area ratio of oxygen containing groups (COOH, C-O and C=O) to C-C group suggested an increased occupation of defects on MWNTs. Transmission electron microscope (TEM) revealed different distributions of Pd NPs on the MWNTs with the variation of Pd(acac)2 amount and the particle size increased with increasing the Pd loading. A relatively higher conversion of Pd(acac)(2) to Pd (76.21%) was achieved when the initial precursor ratio of Pd(acac)(2) to MWNTs was 2 : 1 (product denotes as Pd/MWNTs-(2:1)). The Pd/MWNTs-2:1 catalysts were demonstrated to exhibit the most efficient performance toward ethanol oxidation reaction (EOR) among all the precursor ratios, which is evaluated by the highest Pd mass-based peak current density (1.23 A/mg (Pd)) and stable current density (0.175 A/mg (Pd)) in cyclic voltammetry (CV) and chronoamperometry (CA). In addition, both reduced charge-transfer resistance and increased reaction kinetics with increasing the Pd loading were obtained from electrochemical impedance spectroscopy (EIS) and Tafel characterization. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. All rights reserved.