高性能Fe_(2)O_(3)的制备及其超级电容性能研究

Preparation of high-performance Fe_(2)O_(3)and its supercapacitive properties

Fe_(2)O_(3)具有成本低、无毒、来源丰富、对环境友好等优点,被认为是一种极具应用前景的水系超级电容器负极材料,然而它也存在电导率低、循环稳定性和倍率性能差等缺点。采用水热法和热处理法在碳纸上制备获得了N、S共掺杂的Fe_(2)O_(3)。研究结果表明,N和S掺杂未改变材料的物相,但却使材料的形貌由纳米线组成的网状结构变为一层致密多孔的薄膜。其次,由于导电性的提高和反应活性位点的增多,材料表现出较高的比电容(473.2 mF/cm^(2),2 mA/cm^(2)下)、优越的倍率性能(85.5%,2~20 mA/cm^(2))和良好的循环稳定性(96%,15 mA/cm^(2),10000圈),还具有更高的电化学反应可逆性和库伦效率。最后将N、S-Fe_(2)O_(3)与商业活性炭组装了水系非对称型超级电容器,其体积比电容为2.1 F/cm^(3)(1 mA/cm^(2)下)。将两个组装的超级电容器串联后可以成功驱动一串并联的LED灯(额定电压3 V),实验结果说明该材料具有一定的实际应用价值。

Fe_(2)O_(3)is considered to be a promising negative material for aqueous supercapacitors due to its advantages of low cost,non-toxicity,rich sources and environmental friendliness.However,it also suffers from the disadvantages of low conductivity,unsatisfactory cycling and rate performance.In this paper,N,S codoped-Fe_(2)O_(3)was prepared on carbon fiber paper(CFP)by a hydrothermal method followed calcination process in the presence of thiourea under ambient atmosphere.The results demonstrated that calcination in thiourea didn t change the phase of Fe_(2)O_(3),but changed its morphology from interconnected structure composed of nanowires to a dense film with porous structure.Due to the improved conductivity and the increased reaction active sites,N,S-Fe_(2)O_(3)not only showed high specific capacitance(473.2 mF/cm^(2),2 mA/cm^(2)),superior rate performance(85.5%,2-20 mA/cm^(2))and good cycling stability(96%,15 mA/cm^(2),10000 cycles),but also exhibited higher electrochemical reaction reversibility and coulomb efficiency.Finally,asymmetric supercapacitors were assembled employing N,S-Fe_(2)O_(3)and commercial activated carbon as negative and positive electrode,respectively,and the volume specific capacitance was 2.1 F/cm^(3)(1 mA/cm^(2)).By connecting two assembled supercapacitors in series,a series of LED lights(rated voltage of 3 V)could be successfully lit up,demonstrating its practical applications.