基于偶氮苯-碳纳米复合体的光伏分子储能基础研究

Azobenzeme (AZO) molecules isomerize under the irradiation and store the energy of sunlight through the process of changing from the steady state with low energy to the metastable state with higher energy. The metastable state will return to the steady state and release the stored energy of sunlight of under the stimulation of external factors, like electricity, heat, light, and so on. The energy transformation, storage and releasing in this process can ultimate solar energy uniquely. The aim of this project is to synthesize AZO-carbon nanomaterials hybrids with high energy density and investigate the possibility of the hybrids being applied in chemical energy storage as solar fuels. AZO-carbon nanomaterials hybrids with high photoinduction activation energy are synthesized based on AZO molecules intermolecular hydrogen bonds through various functionalization methods. It will be investigated in detail that the regulation rules of chemical bond, molecular conformation, grafting density, structural parameters and irradiation parameters, such as the polarization, frequency, intensity, to the parameters of the AZO-carbon nanomaterials hybrids such like activation energy, thermal barrier, thermal stability and so on. Subsequently, crucial parameters of the hybrids, such as the energy storage density, the life time of metastable state with higher energy, and the cycling stability, will be figure out, and basic disciplines of energy states transformation as well as chemical energy storage and releasing of the hybrids in the cyclic process of light absorption, retention and emancipation will also be revealed in this project, which will lay research, development and application foundations of AZO-carbon nanomaterials hybrids being applied in photovoltaic energy storage devices as solar fuels.

偶氮苯分子在光激发下会发生异构化转变，从而在低能的稳态跃迁到高能量的亚稳态的过程中将太阳光能储存到化学键内，在受到电、热、光等外界因素刺激时，会释放出相应的化学能回复到稳态，这一能量转换、储存和释放的循环过程表现出独特的光伏储能效应。本项目拟以合成高能量密度的偶氮苯-碳纳米复合体为目标，探索其作为"太阳能燃料"应用于化学储能器件的可行性。以具有分子内强氢键作用的偶氮苯为基础，通过多种功能化方法，制备光诱导高活化能的偶氮苯-碳纳米复合体。系统研究材料的化学键、空间构型、接枝密度，结构参数以及辐照光的偏振性、频率、强度等光照参数对其活化能、热障、热稳定性等特性的调控规律，进而研究其能量存储密度、高能量亚稳态寿命和循环充放特性等关键参数，揭示在光吸收、存储和释放循环过程中的能态演变、化学储能和释放的基本规律，为其作为"太阳能燃料"应用于高效光伏化学储能技术的研发和应用奠定基础。

偶氮苯分子独特的光致异构化转变是实现光热转换、存储与释放过程的关键。针对偶氮基分子存在的光热存储密度低和稳定性差的难点，本项目在分子和结构设计的基础上，利用共价功能化方法获得了一系列偶氮苯/石墨烯杂化分子，通过调控分子级相互作用和空间位阻，实现了光热存储密度和周期的显著提升。（1）合成了6个含不同取代基（磺酸基、甲氧基、羟基和羧基）和分子内/间相互作用与空间位阻的偶氮苯分子，通过改变分子结构实现了光致异构化转变的调控；（2）利用重氮耦合方法，制备了多个偶氮苯/石墨烯光热杂化材料，通过控制分子取代基、接枝密度（1/20）及其在纳米模板上的空间构型，形成了多个分子间氢键，实现了光致异构化转变与回复的速率和程度的控制；（3）获得了光热存储能量密度达到112 Wh/kg，半衰期可达225天，并且可实现绿光诱导快速热释放（5-30分钟可调控）功能的偶氮基光热材料；（4）通过密度泛函理论计算了6种杂化分子的能量密度，最高可达121 Wh/kg，与实验值在一个数量级；（5）总结了分子间氢键和空间位阻对于提高储热密度、稳定性和可控释放特性的规律，揭示了偶氮分子在光吸收、转换、存储与释放循环过程中的结构转变与能量利用基本规律；（6）基于分子设计与结构控制的偶氮基杂化材料为未来设计兼具高能长效存储与可控释放特性的光热转换材料提供了材料基础。