Preparation of platinum nanoparticles on Metal Oxide Loaded Carbon Nanotube for catalysis enhancement of Oxidation in low-temperature Fuel Cells

Abstract

A platinum (Pt) catalyst is an important part in anode catalyst layer for lowtemperature fuel cells. However, the efficiency of these fuel cells mainly depends on the electrocatalytic activities of Pt-based anodic catalysts and low kinetics of small organic molecule electro-oxidation is also the main problem. A critical anode fuel-poisoning problem in this fuel cell systems owing to carbon monoxide (CO) formation upon the electrooxidation of those organic liquid fuels is the also major difficulty. An anode catalyst can be developed by the addition of some metal oxides (MO) into a Pt based catalyst system, which can effectively promote the electro-oxidation. The fuels of small organic molecules used in this work are methanol, ethanol, and formic acid. This work aims to fabricate of effective anode electrocatalyst with low CO formation for low-temperature fuel cell application. The catalyst comprises three components, multiwall carbon nanotube (CNT), Pt and metal oxides (MO) i.e. ceria oxide (CeO2) and coper oxide (CuO), and the prepared catalysts are denoted as xPt−yMO/10CNT where x and y are the quantities of Pt and MO, respectively. The synthesis of electrocatalysts was executed through two steps: attaching of MO nanoparticles onto CNT by the alcothermal method followed by Pt loading onto the metal oxide modified carbon nanotube support by chemical reduction. The oxidation currents depend on the of MO and Pt contents. Among the prepared catalysts and commercial catalysts, the obtained 1Pt–3MO/10CNT electrocatalyst (the 1: 3: 10 mass ratios of Pt, MO and CNT) shows high electrochemical surface area, oxidation activity and stability for the oxidation of methanol, ethanol, and formic acid. The physical characterization of the prepared catalysts was determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrocatalytic performance of the prepared catalysts was examined by electrochemical measurements, i.e., cyclic voltammetry (CV), CO stripping voltammetry and chronoamperometry (CA). The enhancement of the catalytic activity is attributed to changes in the surface electronic structures of Pt and MO on the CNT surface that incrementally affects the active sites for oxidation processes. A required catalytic performance for these oxidations was also observed with small-size and high-dispersion of the Pt catalysts (2-5 nm) on the MO/CNT support nanocomposite. The results also show substantial improvement in the kinetics for oxidations and mass transfer efficiency owing to the improved catalyst structure. These results imply that the prepared catalysts have promising potential for application in low-temperature fuel cells.