基于光电化学水解的MOFs衍生膜修饰光阳极的制备及光生空穴的动力学行为研究

It is the cutting edge of Photoelectrochemical (PEC) or Electrochemical (EC) water splitting to face the exhausted fossil energy. One of the factors who constraining photoanodes’ water splitting performance is the hysteresis effect from the trapped photo-generated holes by the anodes surface states, which induced by photo-corrosion during the oxygen evolution reaction (OER). To address this issue, it was concluded to be worked through coupling a layer of OER catalyst film on the surface of photoanodes. In this project, we plan to cover a layer of metal-organic frameworks (MOFs) derivate film, as the OER catalyst, on the pristine CdS1-xSex nanowhisker sensitized N-doped TiO2 nanorod arrays (M-NC/CdSSe/NT NAs) for water splitting. With the help of the stable electrochemical properties of the OER film, i.e. M-NC, on the one hand, the surface states of the CdSSe/NT would be passivated effectively. On the other hand, the kinetic characteristics of photo-generated holes could be improved via the efficient oxygen storage and release ability of M-NC. Through the comparative study of PEC water splitting properties of M-NC/CdSSe/NT and that of pristine CdSSe/NT, One can expect to reveal (1) the modulation mechanism of OER film to the kinetic behavior of photogenerated holes, and (2) the structure-function relationship of OER catalyst and the PEC anodes capabilities for water splitting. Further, one could establish a new approach to discern how to couple the OER catalyst film and the photoanodes optimizedly for promoting the energy conversion efficiency and the working stability of PEC system.

面对化石能源枯竭及环境污染问题，光电催化（PEC）水解制氢，同时利用太阳能与剩余电能，是水解制取氢能的重点研究内容之一。迄今，制约PEC光阳极水解性能的因素之一是光腐蚀诱导产生的表面态对光生空穴（h+）动力学性能的迟滞作用。针对这一问题，本课题拟建立析氧（OER）催化剂膜修饰下PEC光阳极制备的新方法。设计、可控制备多种MOFs衍生物薄膜（M-NC、MOOH-NC、MN-NC、MP-NC），作为OER催化剂膜，修饰CdS1-xSex 敏化的N-doped TiO2纳米阵列光阳极。利用 OER 膜稳定的电化学性能，实现对光阳极表面态的有效钝化；利用OER催化剂高效的氧存储和释放能力，实现对光生空穴动力学性能的显著提升；运用先进的表征手段，阐述目标光阳极物化性能的演变规律；建立高效、稳定的复合PEC水解电极的制备方法。获得：（1） OER 膜对表面态及 h+动力学行为的调制机制，揭示OER膜与PEC光阳极水解性能间的构效关系；（2）建立识别 OER膜与光阳极优化耦合的新方法， 实现 PEC 系统能量转换效率及工作稳定性的提高。

氢能是面对化石能源枯竭及其相关的环境污染问题，实现国家碳中和的发展目标的有效方法之一。而通过光电化学（PEC）和电化学（EC）水解制取氢气一直是新能源领域的研究热点。本项目通过通过综合气氛氮化退火，实现对高导碳布（CC）衬底上生长的TiO2纳米棒阵列（TiO2 NRAs）的可控N掺杂。研究发现NRAs晶体结构随N掺杂量的提高而呈现规律性变化，进而材料的价带边也呈现规律性改变。进一步通过物理/化学气相沉积（PVD/CVD）实现可见光响应的CdSSe敏化（CdSSe/NT NRAs），IPCE/ ABPE证实了N掺杂与CdSSe敏化对光阳极PEC性能的协同增强作用；暗电流分析确认Type II类型带边连接结构，能够有效促进光生载流子的定向传输与分离及光生空穴（h+）的OER反应动力学性能。气氛碳化-氧化Co-MOF（ZIF-67）得到钴/钴氧化物NPs镶嵌的N-doped C NRAs膜（Co/NC & Co-O/NC）。Co-O/NC由于Co-O/NC预氧化中形成更强的Co-O键，不利于表面重构形成OER活性的羟基氧化物相，进而阻碍其对水氧化中间体的有效吸附与解吸附。进一步通过La, Ce, Nd修饰制备多种MOFs衍生物膜（La/Co/NC、Ce/Co/NC、Nd/Co/NC NRAs），研究其对电极水解（HER/OER）过程中的表活性和比活性影响规律。研究发现，尽管三者原子序数近邻，其负载对Co/NC NRs的形貌，晶体结构有着不同影响结果。其中Ce对电极的几何电流密度影响较大；Nd对载流子的动力学性能及活性位恢复能力影响较大；而La对电化学比表面积（ECSA）归一化电流密度有较大的影响。本为设计和制造高性能的PEC器件，为载流子水解动力学的研究和其他新能源领域电极的制备等技术提供理论和实验依据。