1. School of Chemistry and Chemical Engineering，Xinjiang Normal University，Urumqi 830054，China
2. Xinjiang Key Laboratory of Energy Storage and Photoelectrocatalytic Materials，Urumqi 830054，China
Abstract：With the increasing depletion of fossil fuels, the demand for energy in human society is increasing. In order to balance the energy application demand and improve the energy efficiency, the development of high-efficiency energy conversion materials and electrochemical energy storage materials has become an important research topic. Conductive polymer based electrode materials face the challenges of low energy and power density and poor cycle performance in corresponding energy storage devices. Structural modification is needed to improve their conductivity and interface properties. Since the electronic structure, optical and electrochemical properties of conjugated polymers are determined by the skeleton structure of conjugated chains, the structural modification of conductive conjugated polymers to improve their charge transport properties and carrier mobility, and then the design and synthesis of new high mobility conductive polymer based conjugated polymers is the key to improve the characteristics of their corresponding devices. Most of the reported studies use complex structural design to improve mobility. In this paper, a new narrow-band gap polybenzidine based conjugated polymer with simple structure and helpful to improve charge transfer was designed and synthesized. The structure and properties of the materials were characterized by spectroscopic and electrochemical methods. The structures of the monomers and polymers were characterized by 1H NMR, FTIR and X-ray powder diffraction. Their optical and electrochemical properties were tested by UV-vis spectrum, UV-vis diffuse reflection, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectrum. The results show that the conjugated polymer with the expected structure is successfully prepared, and the obtained polymer has good crystallinity. The optical band gap Egopt is 1.85 eV, and the HOMO and LUMO energy levels are -5.44 eV and -3.75 eV, respectively. The former is higher than the values published in literature, while the latter is lower than most literature values, indicating the polymer presents the structural characteristics of promoting p-type and n-type doping at the same time, and has the performance advantage of enhancing the charge holding capacity of the material. The energy storage properties of polymers are affected by chemical structure, crystal structure and micro morphology. The microstructure characteristics of polybenzidine based conjugated polymer helps to improve their electronic conductivity, but its morphological characteristics of layered dense blocks limit their ionic conductivity. The electrochemical performance test results show that the polymer has certain electrochemical activity, small charge transfer impedance and basically meets the conditions for smooth ion diffusion. The discharge specific capacitance at 0.05A/g is 256.6F/g. The results show that the prepared polybenzidine based narrow band gap conjugated polymers have broad application prospects in photoelectric conversion, energy storage and micro-electronic devices.
Key words：Benzidine based；Conjugated polymer；Narrow band gap；Electrochemical perfomance
