新型类水滑石/活性炭复合材料制备及CO2捕集与光催化性能研究

Layered double hydroxides (LDHs) and activated carbon (AC) are found to be the most application prospect of solid adsorbents for CO2 capure. How to efficiently increase the capacity of the adsorbent and CO2 conversion efficiency is the key to restrict application and popularization of the adsorption materials in carbon capture, utilization and storage (CCUS). This project proposal aims to solve the above problem by designing and synthesizing a new type of hydrotalcite, Ti/Li/Al-LDHs with photocatalytic performance, and using co-precipitation method to preparation a new hybride composite (Ti/Li/Al-LDHs/AC) having the double function of CO2 capture and photo-catalysis for CO2 conversion into methane. Through the research of the key factors affecting the materials preparation, the effect of the composition, structure and morphology of Ti/Li/Al-LDHs/AC and pore structure and surface functional group structure of the ACs on CO2 capture and photo-catalysis coupling characteristics of the composite materials will be illustrated, and the relationship and controllable methods between structure and performance of the composite materials will be found; Synergistic reinforcement mechanism of CO2 adsorption and its photocatalytic reduction into methane with water vapor on the composite materials and kinetics of adsorption and photocatalytic reaction will be found by using quantum chemical methods and molecular dynamics simulations; Furthermore, thermal stability and regeneration mechanism of the composite materials will be illustrated by studying the relationship of composite material structure and products selectivity for supplying theoretical foundation of the composite material application.

类水滑石（LDHs）和活性碳（AC）是目前发现的最具有应用前景的CO2固体吸附剂。如何提高吸附剂容量和CO2转化效率是制约该类吸附材料在碳捕集与利用领域推广应用的关键。为此，本项目提出设计合成一种具有光催化性能的新型类水滑石Ti/Li/Al-LDHs，并用共沉淀法制备具有CO2捕集和光催化制甲烷双重功能的新型杂化复合材料(Ti/Li/Al-LDHs/AC)的新思路。通过材料制备关键影响因素研究，阐明Ti/Li/Al-LDHs/AC组成、结构和形貌，AC孔结构和表面官能团等变化对复合材料CO2捕集和光催化耦合特性影响规律，建立材料结构与性能关系及其调控方法；采用分子动力学模拟和量子化学方法，探明复合材料CO2吸附与光催化水蒸汽还原反应过程的协同强化机理及吸附与光催化反应动力学；进一步结合复合材料结构与产物选择性关系研究，探讨复合材料光热稳定性及再生机理，为促进复合材料应用提供理论基础。

CO2捕集与光催化转化一体化技术是实现CO2减排和利用的有效途径。项目重点开展了层状双羟基化合物（LDHs）及多孔炭复合材料结构与CO2吸附和光催化协同作用研究，探讨了元素比例、pH值、焙烧温度和多孔炭结构等因素对Ti/Li/Al-LDHs及多孔炭复合材料结构和性能的影响规律。研究成果对减少CO2排放，实现碳中和具有重要理论和实际意义。. 以延迟焦（DC）为载体制备了Ti/Li/Al-LDHs /DC复合材料，发明了CO2捕集与光催化转化一体化装置。与Ti1Li3Al2-LDHs相比，Ti1Li3Al2-LDHs/DC具有更佳光催化性能，CH4产率明显提高。Ti1Li3Al4-LDHs层板间阳离子电荷密度分布不均匀，晶胞变形，有大量氢键。C掺杂使Ti/Li/Al-LDHs /DC晶体结构稳定性增强，对称性变差，晶格缺陷增加。Ti/Li/Al-LDHs /DC界面作用、晶格缺陷和孔结构等因素是导致其有良好光催化性能的根本原因。.以椰壳活性炭(BAC)为载体，丙三醇为导向剂制备出了Ti1Li3Al2-LDHs@BAC复合材料。添加BAC和焙烧处理有利于提高Ti1Li3Al2-LDHs的CO2吸-脱附性能。Ti1Li3Al2-LDH的CO2吸附行为符合颗粒内扩散模型。. 以煤质活性炭、BAC及其氧化改性炭（OBAC）为载体制备了Ti1Li3Al4-LDHs@AC复合材料，探明了形成机理和结构模型。BAC更有利于提高Ti1Li3Al4-LDHs@AC性能，当LiNO3与BAC质量比为3:1时，复合材料性能最佳。Ti1Li3Al4-LDHs@OBAC6HNO3光催化CO2还原为CO和CH4产率最高，分别可达到78.47 μmol/gcat和5.92 μmol/gcat。这是因为OBAC表面有丰富含氧官能团，促进了复合材料界面键合作用，提高了空穴和电子对的分离效率。材料表面活性位上光生电子密度越大，CH4产率越高。. 光催化CO2还原反应动力学符合Langmuir-Hinshelwood一级动力学模型。经600 h反应后，Ti1Li3Al2-LDHs@OBAC仍呈现出良好水热光稳定性。探究了Ag/Ti1Li3Al4-LDHs 和CDs/Ti1Li3Al2-LDHs结构与性能的关系，为该材料改进指明了方向。