基于"光聚集-气富集"策略的CH4-CO2光催化转化研究

Photocatalytic conversion of CH4 and CO2 is significant both for energy development and environmental remediation. However, the current photocatalytic system is hard to achieve a high coupling conversion efficiency due to the simple strucuture and characteristics of photocatalysts. This project proposes to design and prepare hollow microarrays of bimetal-containing Ti-based photocatalyst through nanocasting and layer-by-layer self-assembly technologies for the coupling conversion of CH4 and CO2, which is based on the common application base of porous Ti-based photocatalysts both in the non-coupling conversion of CH4 and CO2 and the respective structure properties of the reactants. The light-collecting and gas-enrichment effect will be used to improve the coupling conversion efficencey. The light-collecting effect refers to improving the light-absorption efficiency of the interior active center through the multiple light scattering effect of the hollow cavity. The gas-enrichment effect means to enrich CO2 by alkaline metal ions and activate C-H bond of CH4 by light-responsible metal ions. Finally, assisted by light-range broadening strategy, the conversion efficiency of CH4-CO2 will be improved by sufficient radicals produced from intensive light irradiation. Through revealing the relation between structure (architecture, constituent and surface/intersurface property) and activity (conversion efficiency and selectivity), and explain the reaction process and conversion mechanism, we hope to achieve a solid progress on photocatalytic coupling conversion of CH4 and CO2 and lay a theoretical foundation for the development of more efficient photocatalysts.

CH4-CO2光催化转化具有能源开发及环境治理的双重意义，但当前所用催化剂结构性能单一，难以实现两种高稳定分子之间的高效耦合转化。申请者拟从现有在CH4、CO2非联合转化中兼具应用基础的钛基多孔光催化剂出发，针对反应分子结构特性，采用纳米浇铸-层层自组装技术构建空腔型双金属掺杂钛基多孔有序阵列，利用阵列的“光聚集”及“气富集”效应提高双分子协同转化效率。“光聚集”指利用空腔的多重光散射效应增强催化剂内部光活性中心的光吸收；“气富集”为利用骨架碱性金属离子实现CO2的富集、具有光驱动C-H键极化能力的金属离子实现CH4的活化。最终，结合吸收光谱拓宽手段，利用宽光谱“光聚集”下产生的高浓度自由基提高两者协同转化效率。通过揭示催化剂结构组成、表/界面性质与转化率、选择性之间的构效关系，阐明反应历程及转化机制，实质性推动光催化技术在CH4-CO2转化中的应用，为更高效光催化体系的开发提供理论基础。

将甲烷与二氧化碳进行协同转化不仅能缓解温室效应，还能制备碳氢化学品。传统热催化过程耗能巨大、催化剂易积碳失活，反应体系存在严重的高能耗低产出的问题。光催化反应可利用光子能量在低温下催化转化甲烷与二氧化碳。然而，传统光催化剂难以同时活化这两种高度对称的反应物分子。本项目主要根据“光聚集-气富集”策略展开研究，利用空腔结构增强光吸收效率，可通过骨架及表面结构性能调控，达到提高两种高稳定反应物分子在催化剂表面光驱动极化-活化效率的目的。研究内容主要包括：（1）构建了Ga掺杂及Pt负载的大孔-介孔TiO2-SiO2，探究掺杂及负载改性策略对催化剂电子结构调控、甲烷活化方式的影响；（2）设计并制备不同元素掺杂的TiO2-SiO2，探究掺杂类型对甲烷转化效率及作用机制的影响；（3）制备了Pt负载的Ga2O3，探究了Pt纳米粒子几何构型及电子结构对甲烷吸附及乙烷解吸的影响。相比于传统光催化剂，本项目开发的甲烷-二氧化碳转化光催化剂具有高活性、高稳定性、高选择性的优势。本项目的研究将为开发高效甲烷-二氧化碳转化光催化剂提供新思路，推动光催化能源转化的发展应用。