静电纺功能化碳纳米纤维及不对称电容器淡化苦咸水研究

Faced with the severe problem of water resources and energy shortage, supercapacitor desalination (SCD) technology with high desalination efficacy and less energy consumption is viable to produce fresh water from brackish or sea water, because of its excellent features such as operational simplicity, environmental friendliness, energy recyclability during discharging (regeneration) process. The electrospun film is an ideal material for preparing the porous carbon fiber electrode for supercapacitor, due to its advantages such as three-dimensional nanofiber structure, high specific surface area and components adjustability. In this project, the electrospinning technique is adopted to prepare the functionalized carbon composite fiber containing additives such as S, N and transition metal compounds. The positive and negative electrode materials are screened based on the difference of the Zeta potential and adsorption behavior of the composite electrode. The assembled asymmetric supercapacitor with positive and negative electrode pairs can be used for desalting. The additives can improve the pore size of carbon fiber, thus enhancing the effective adsorption capacity, and the increased net charges on carbon surface due to the formation of different heteroatom products result in the increase of the active sites for ions adsorption and transmission(i.e. ionic conductivity), while suppressing the counter ion movement and thus increasing the charging current efficiency. With the study of carbon morphology, electrochemical properties and adsorption behavior, the material selection rules for the positive and negative electrodes can be explored， and the desalination process theory of the asymmetric capacitor will be understood. Finally, through the study of the adsorption-desorption behavior of different ions and the analysis of the polarization process in the SCD setup, the applicability to brackish water desalination can be demonstrated. The research program can provide an important theoretical basis for actual application in brackish water desalination.

超级电容器不仅可淡化苦咸水，而且再生过程能量可回收，对解决淡水资源、能源短缺问题具有重要意义。静电纺丝膜具有三维纳米纤维结构、高比表面积、成分可调等优点，是制备超级电容器电极的理想材料。本项目拟采用静电纺技术，制备含N、S及过渡金属等功能化碳纳米纤维电极。以所得功能化碳复合电极的Zeta电势及吸附行为不同，筛选正负极材料并组装不对称超级电容器，研究脱盐性能。添加剂在碳化过程中不仅改善碳表面孔径、提高吸附电容，而且杂原子产物形态改变了碳表面的净电荷分布，增加离子吸附的有效点位及表面离子传输性（离子导电性），提高电极有效吸附容量、降低电阻；同时抑制反离子作用，增大脱盐及电流效率。通过碳材料形貌、电化学性质及吸附行为研究，探索不对称电容器电极正负极材料筛选一般规律及脱盐过程相关理论。通过不同离子的电吸附行为及电极极化过程研究，分析其对苦咸水淡化的适用性，为苦咸水淡化实际应用提供重要的理论依据。

水资源问题是关系国家经济可持续发展和社会长治久安的重大战略问题。苦咸水淡化对解决水资源问题意义重大。超级电容器去离子技术由于具有低的能耗，高的水回用率，在实现海水苦咸水淡化、解决淡水资源危机等方面具有很大应用潜力。本项目采用静电纺丝技术，通过在纺丝液中添加不同造孔剂如聚苯乙烯，聚甲基丙烯酰胺，环糊精，二甲砜等以改善碳化纤维的孔结构，提高比表面积，从而提高纤维表面的活性位点；通过添加Zn盐、Ni盐或纤维表面的MnO2修饰改性等，以制备过渡金属化合物修饰碳纳米纤维电极。所得纤维表面金属氧化物纳米颗粒均匀分布。采用Zeta电位仪及电化学方法分析修饰材料的Zeta电势的不同，从而筛选阳极及阴极材料，组装不对称超级电容器并实现了高效电容器脱盐。由于杂原子基团及金属氧化物在纤维中的修饰，从而可以方便调节电极表面的静电荷分布，有效抑制反离子作用，所对应的不对称电容器的脱盐容量及电流效率大大提高。杂原子的存在提高了电极表面的亲水性，有效降低了电解质与电极表面之间的界面电阻，提高了电荷迁移速度。通过分析不同操作条件下的脱盐现象，探索反离子影响规律，并阐明了相关反离子影响机理。本课题揭示了电容器脱盐中反离子影响的关键科学问题。并率先提出了脱盐过程中的极化规律以及由极化带来的pH及电导率的变化对脱盐影响。为以后的苦咸水及海水脱盐系统优化操作提供重要的理论依据。