Electrosynthesized ZnO/p-Type Conductive Polymer Nanocomposite with Enhanced Catalytic Activity of Methanol Oxidation in Alkaline Media

The direct methanol fuel cell (DMFC), as an effective power source, has been attracting considerable attention for several decades, due to its high efficiency, very low polluting emissions, potential renewability as a fuel source, simple operation and ease of storage. The slow kinetics of the methanol oxidation reaction and poisoning of active sites with residual intermediates are two major problems with respect to the commercialization of DMFCs. The success of fuel cell technology depends strongly on electrocatalysts, which can lower electrochemical over-potentials and produce high voltage outputs. Therefore, the design of a catalyst with improved electrode kinetics for methanol oxidation and enhanced efficiency, stability and durability is highly desirable [1-3]. Herein, we describe a simple and facile strategy for synthesis of nanocomposite of poly ortho aminophenol (POAP) and ZnO nanoparticles namely (POAP/ZnO). Electropolymerization of nanocomposite was carried out by cyclic voltammetry (CV) method from an electrolyte containing ortho aminophenol and ZnO nanoparticles. Surface morphology of the composite film was studied by surface microscopy techniques and the presence of ZnO in the films was confirmed by EDS analysis. Furthermore, the fractal dimension of nanocomposite films in the presence of counter ions was investigated. To elucidate the effect of ZnO on the property of POAP films, the electrochemical performance of composite films was evaluated by carrying out CV measurements in 0.1 M HCl. Close comparisons of CV curves between POAP/ZnO electrode and pure POAP electrode show that a POAP/ZnO electrode not only displays a higher background current in the potential sweep but also there exist faradic currents, which are believed to arise from the contribution of the loaded ZnO. The results indicate that a strong interaction exist at the interface of POAP and nano-ZnO. In comparison with a Ni-POAP electrode, a Ni- POAP/ZnO electrode shows a better catalytic performance for the electrocatalytic oxidation of methanol in alkaline solution. 218 The larger methanol response at the Ni- POAP/ZnO electrode with respect to the POAP electrode is proposed to be due to the Ni- POAP/ZnO enhancing the electrochemical activity of the Ni2+/Ni3+ redox reaction through fine dispersion of the particles into the conductive polymer matrix, resulting in a drastic increase in surface area. It is observed that in the presence of ZnO nanoparticles current density of electro-oxidation of methanol is almost constant in 400 cycles due to the stability of electrocatalyst in this cycle number and indicating that methanol reacted with the surface and no poisoning effect on the surface was observed.