人工仿生制氢中敏化钛基电极的界面行为和建模调控

Artifical photosynthesis can fulfill the dream of an eco-friendly world for humanity. Solar splitting of water to hydrogen and oxygen based on inorganic semiconductor materials is one of the promising routes of artifical photosynthesis for solar energy conversion and chemical fuel production. However, artificial photosynthetic systems in general require dramatic improvements in energy conversion efficiency before they can be considered for practical applications. The great challenge is to fabricate supramolecular collectors of light and separate efficiently the light-generated charge carriers, which is very crucial to increase the energy conversion efficiency for artificial photosynthetic systems. The project will employ the tools of chemistry, and materials science, and the fundamental principles of engineering thermodynamics underlying energy conversion to build and manipulate sensitized TiO2-based photoelectrodes which play a vital role in absorbing light and transfering charges in photoelectrochemical (PEC) hydrogen production systems. In order to make similar-to-natural photosynthetic systems, this project will focus on the design and fabrication of sensitized TiO2-based photoelectrodes using dyes and quantum dots (QDs), or hybrid dye/QD assemblies, which can absorb in a broad wavelength range aross the solar spectrum. Particularly, for the first time novel and low toxicity visible-NIR responsive AgInS2 QDs will function as sensitizers for hydrogen-evolving electrodes. The coupling of multifunctional TiO2 nanotube photonic crystals to nanocrystalline titania layers is applied to be an effective way to enhance light harvesting and ultimately solar power conversion efficiency. On the other hand, the project will focus on investigating the interface behaviors and modeling of sensitized TiO2-based photoelectrodes through experimental studies combined with numerical simulation calculations. In PEC hydrogen production systems, the parameters and the constituents of the photoelectrode interface relative to the TiO2 film, sensitizer and electrolyte not only affect the absorption of sunlight but also bring about complex interface behaviors including electron injection, electron transfer, electron relaxtion, energy loss, carrier multiplication, etc. The project will model the interfacial behaviors of photoelectrodes with a mesoscale, nanoscale, and multiscale simulation approach to explore electron and phonon transport, as well as fluid particle energy storage, transport and transformation kinetics. With the experimental data modification based on our interface analysis, an ideal interface model of TiO2 film/sensitizer/electrolyte will be established to help to provide effective and feasible methods of regulating and controlling the interface parameters for enhanced overall energy conversion efficiency of the artificial photosynthesis process.

人工光合作用是人类自主实现太阳能转换和利用并具有重要意义的环境友好能源技术。为了发展基于无机半导体材料的人工光合作用体系，本项目以仿生光电化学制氢系统中钛基光电极为研究对象，着重研究：（1）基于材料创新，在TiO2纳米管阵列及纳米晶孔膜上组装染料、量子点或染料/量子点耦合敏化剂以构建新型敏化钛基光-氢电极，使TiO2膜/敏化剂/电解液的复杂电极界面上达到太阳能全谱吸收与有效电荷分离的协调统一；（2）基于方法创新，将实验研究和建模计算相结合，不仅基于时间分辨光谱分析所组装的光-氢电极界面的电子注入、电子弛豫、电荷迁移、电荷增值及界面能损等界面行为，而且从纳米、中孔及多尺度数值模拟分析电极界面的能量传递过程，以期基于化学材料科学和工程热物理基本原理发展在电极界面上光子、电子、声子和流体粒子进行能量存储、输运和转换的理想模型和可控规律，从而为提高人工仿生制氢体系能量转换效率提供新的途径和理论。

通过人工光合作用进行太阳能转换利用和氢能清洁制备是能源可持续发展的重要途径。为了发展基于无机半导体材料的人工光合作用体系，本项目主要研究仿生光电分解水制氢系统中的敏化钛基电极的设计和制备、电极/敏化剂/电解液界面行为和界面能量模型以及敏化钛基电极的仿生制氢效率。研究结果包括（1）基于碳点和Cu基材料的环境友好性和优良的光电转化性质，以染料Eosin Y（EY）和量子点（C dots）/纳米材料（Cu-CuO）进行耦合构建得到具有太阳光宽谱吸收特性的新型敏化钛基电极C dots/EY/TiO2 NTs和EY/Cu-CuO/TiO2 NTs，其光电性能均优于单一敏化的TiO2纳米管阵列（TiO2 NTs）电极，在C dots和Cu-CuO增强钛基材料对EY吸附的同时可增加电子扩散系数、延长光生载流子寿命和减少电子传输时间。（2）基于EY、C dots、Cu-CuO和TiO2的能级，建立了C dots/EY/TiO2 NTs和EY/Cu-CuO/TiO2 NTs电极的界面能量模型，与界面行为、光电性能和制氢效率相结合，揭示了先EY后C dots的敏化顺序与高效电子传输性能的关联以及Eosin Y对Cu-CuO/TiO2 NTs 电荷传输的优化作用。（3）相对刮涂法制备的TiO2纳米粒子膜电极基体，阳极氧化法制得的TiO2 NTs基体可沉积更多的C dots而具有更好的光敏性和光电性质；通过两步阳极氧化法优化TiO2 NTs制得的TiO2 环管分层结构（TiO2 R/T）可增加对EY的吸附，而TiO2 R/T的可见光活性取决于材料缺陷和掺杂引起的可见光吸收而非具有光子晶体特点的振荡峰；通过飞秒激光物理沉积法，在较高室压1mbar下沉积3h得到的金红石型TiO2粒子膜（314nm膜厚）具有更为分散的不同粒径纳米粒子堆积形态而具有较优的界面电荷传递行为，使得其具有混晶型TiO2NTs电极（650nm膜厚）相近的光电流密度。（4）应用经典分子动力学，对TiO2-水界面和TiO2-KOH水溶液界面进行分子动力学模拟计算，获得了动力学界面结构和水/K+的扩散系数以及亥姆霍兹层的宽度和势降，通过建立TiO2与水溶液界面能量模型对界面亥姆霍兹层和耗尽层进行了关联，计算得到与电荷扩散和分离相关的耗尽层宽度，从微观角度阐明和理解了电极-电解液的相互作用和界面性质。