Abstract:

Glucose-based carbon spheres (GCs) with size about 500nm were synthesized by one-step hydrothermal method using glucose as the precursor. Polystyrene microspheres (PSs) with diameter about 270nm were obtained by microemulsion polymerization. The multi-stage template assembled by GCs and PSs was prepared by vacuum filtration. TiCl₄ was completely infiltrated into the template, and the TiO₂ with hierarchical pore structure was fabricated after dry and calcination. The morphology, composition and pore structure of the catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N₂ adsorption-desorption. Photocatalytic reduction experiments were carried out in the presence of saturated CO₂ and H₂O under simulated sunlight condition. The results showed that after 7h photocatalytic test, compared with commercial P25-TiO₂ and TiO₂ without spatial structure, the TiO₂ with spatial porous structure had a significantly higher production rate of CO. Among them, in the case of structure mismatch, the multistage porous TiO₂ also showed high CO yield. Combined with the experimental results and characterizations, it was confirmed that the hierarchically porous TiO₂ assembled by nano spherical layers had a high specific surface area and rich pores, which were conducive to the formation of abundant surface active sites. The defect of oxygen vacancies exposed on the porous TiO₂ with 3D net-like structure provided effective carrier transport channels, enhanced the separation of photogenerated electrons and holes, promoted the participation of photogenerated electrons in the reduction process, and finally improved the CO₂ conversion.

Key words: photocatalysis, CO₂ reduction, hierarchical space, TiO₂ pore-structure

摘要：

以葡萄糖为原料，经一步水热法生成葡萄糖基碳球（GCs），粒径约500nm，利用微乳液聚合法合成粒径约270nm的聚苯乙烯微球（PSs）。通过真空抽滤，制备了GCs和PSs层层组装的多级模板，TiCl₄完全浸润模板并经干燥和高温煅烧，获得了空间层序多级孔结构的TiO₂。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、N₂吸附-脱附等手段表征了所制备催化剂的形貌、组分和孔结构。在饱和CO₂气氛下加入H₂O，利用催化剂在模拟太阳光条件进行光催化还原试验。结果表明：经过7h的光催化测试，相较于商用P25和无空间结构的TiO₂，层序空间多孔TiO₂生成还原产物CO的产率均得到明显提高。其中，空间复合多级孔TiO₂在结构失配的情况下仍表现出较高的CO产率。结合实验结果和表征证实：纳米微球层所形成的层序空间多孔TiO₂具有较高的比表面积和丰富的孔结构，有利于形成大量表面活性位点。三维网状多孔结构暴露出的氧空位缺陷提供了有效的光生载流子传输通道，增强了光生电子和空穴的分离，促进了光生电子参与还原过程，最终提高了CO₂转化为CO的效率。

关键词: 光催化, CO₂还原, 层序空间, TiO₂多孔结构