The Magnetic And Supercapacitor Properities Of Polypyrrole-metal Composite Nanowire Arrays In AAO

The research of organic-inorganic composite nano-materials has been an important part of the Materials Engineering. One of the organics researched is the conductive polymer polypyrrole, which has been focused on because of its low price, environmental friendly, stability, and the adjustable conductance etc. The polypyrrole based composites have been widely used in microwave, sensor, metal corrosion, electrochemical supercapacitors. In this work, we synthesized polypyrrole-metal composite core-shell nanowires, and studied its hard magnetic performance and supercapacitor properties. It is found that the composite nanowires have enhanced magnetic performance and supercapacitor capacity.In our work we try to co-electrodeposition FeCo and polypyrrole under an AC electric field in the aluminum oxide template (AAO), with the mixed solution of Fe2+, Co2+ and the pyrrole monomer. Subsequently, the nanowires were characterized by X-Ray, IR-Infrared spectrometry, Transmission Electron Microscope, etc. The experiments show that the nanowires are composite and contain both FeCo and polypyrrole. The High-resolution Transmission Electron Microscope (HRTEM) shows that the nanowires are core-shell with polypyrrole the coating layer. In the same way, we also synthesized core-shell polypyrrole coated cobalt nanowires. The possible growth mechanism may be that, pyrrole monomer is oxidized in the positive part of the AC electric field, while metal ions were reduced in the negative part of the AC electric field. The hard magnetic properties of the composite nanowires were also been characterized. It is found that the polypyrrole-coated metal nanowire arrays have enhanced magnetic performance. We believe that the enhancement is ascribed to the reduction of the dipole interaction between nanowires after the introduction of non-magnetic polypyrrole layer.We prepared free-standing polypyrrole (PPy) nanowire arrays, as well as the core-shell Co/PPy arrays in the Ti/W/Al2O3 templates, and research the supercapacitor performance of them. The study found that, at the voltage scanning rate of 50 mV/s, the cyclic voltammetry curve of the free-standing polypyrrole nanowire arrays are rectangular, with a capacity of 6.6 mF/cm2. Based on the study, we think the supercapacitor properties of the free-standing polypyrrole nanowire arrays are pseudo-capacitive with good redox reversibility, however, with poor charge-discharge cycling stability. Nevertheless, if we co-deposite cobalt and polypyrrole in Ti/W/Al2O3 templated by an AC electric field, we have an enhanced capacity of 13 mF/cm2 at the same scaning voltage rate, together with a good charge-discharge cycling stability. We mink there are two reasons for the enhancement:(1) the interleaving growth of cobalt and polypyrrole in the co-deposition process, in which the contact resistance of cobalt and polypyrrole is reduced, which improves the migration efficiency of charges on the electrode; (2) the conductance of Co/PPy composite nanowires is dependent on the cobalt which has good conductivity. In addition, for the co-depositioned Co/PPy composite nanowire arrays grown in AAO template, we removed its A1 base and the alumina barrier layer, and sputtered golden electrode instead. The capacitance has enhanced and reached to 78 mF/cm2, however, the redox reaction has become irreversible with poor cycling stability. We think the redox is related to the redox reaction of cobalt. The mechanisms should be further explored.