Preparation and characterization of manganese dioxide (MnO_2) as a cathode catalyst for direct methanol fuel cells

摘要

Manganese dioxide (MnO_2) was studied for a cathode catalyst in direct methanol fuel cells (DMFCs) in order to substitute the high activity but high cost platinum (Pt) catalyst. MnO_2 was synthesized by the precipitation method, calcined, and characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS), including X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), and in-situ XANES. From XRD and XAS, the results showed that the precalcined and calcined MnO_x were in the phase of MnCO_3 and MnO_2 respectively, and the precalcined MnO_x was transformed from MnCO_3 to MnO_2 completely at 300°C. The electrochemical performance was measured by the cyclic voltammetry (CV) technique, showing an oxygen reduction reaction peak at -0.8 V with an electric current of -0.015 A. There was no anodic peak in the methanol solution, showing that MnO_2 did not active with the methanol oxidation.