Graphene quantum dot functionalized by chitosan and beta-cyclodextrin as a new support nanocomposite material for efficient methanol electrooxidation

Abstract

Current needs for sustainable energy have popularized the development and use of fuel cell technology. Catalysts are vital fuel cell components, and in recent years research efforts have focused on the development new types of catalysts. This work describes application of a novel nanocatalyst based on graphene quantum dot functionalized by chitosan (GQD-CS) and beta-cyclodextrin (GQD-beta-CD) towards electrooxidation of methanol in alkaline solution. The catalysts were prepared by cycling the glassy carbon electrode in solutions containing graphene quantum dot and chitosan. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of methanol, the modified electrodes [(GQD-CS-GCE) and (GQD-beta-CD-GCE)] exhibited a significantly higher catalytical response for methanol oxidation compared to the other samples. The anodic peak currents showed a linear dependency on the square root of the scan rate, which is a characteristic of a diffusion controlled process. The graphene quantum dots functionalized with chitosan and beta-CD electrodes is further extended to the demonstration of novel electrocatalyst through the transfer of the electrode fabricated by bare GQDs. For comparison of the recognition efficiency, other electrodes including bare GCE, and GQDs-GCE were used for the control experiments. Comparison of recorded CVs and CHs in the presence of methanol using GQD-CS-GCE, beta-CD-GQDs-GCE shows Delta E-p was decreased as GQD-CS-GCE > GQDs-beta-CD-GCE > GQDs-GCE. The higher peak current observed in the presence of GQD-CS-GCE, GQDs-beta-CD-GCE clearly indicates beta-CD and CS essential roles in the observed electrocatalytical behavior. In general, the attachment of chitosan and beta-cyclodextrin to structure of GQDs provides new opportunities towards the direct methanol fuel cell application. (C) 2016 Elsevier B.V. All rights reserved.