Abstract Nanoporous TiO2 spheres have emerged recently as a new class of TiO2 nanomaterials for photochemical applications. Compared with conventional TiO2 nanoparticles, the spherical assemblies consisting of low-dimensional nanocrystallites present significant advantages in terms of structural isotropy, monodisperse nature, structural diversity on nano- and (sub)micro-scales, structural stability, light harvesting property, interconnected nanobuilding blocks with less grain boundary, and easy reclaim. Superior performances have been demonstrated in the fields of photoelectrocatalysis and photovoltaics. Research efforts have been devoted to the rational design of a synthetic strategy for the facile preparation of nanoporous TiO2 spheres. The last decade has witnessed rapid progress in developing a synthesis strategy of nanoporous TiO2 spheres for optimal photochemical applications. Both chemical and physical routes have been extensively developed aiming to ease control over the self-assembly of nanobuilding blocks and, thus, the resultant textural properties and physicochemical performances of the nanoporous TiO2 spheres. In this review, a comprehensive description of different synthetic strategies is first presented, with a special emphasis on the formation mechanism, in particular, the pathway followed by nanocrystallites to self-assemble into a spherical structure. Notable experimental parameters are also discussed for the reproducible and controllable preparation of nanoporous TiO2 spheres with well-defined hierarchical structure, tunable porous microstructure from assembled nanobuilding blocks, and optimal physicochemical properties. Important applications in environmental photocatalysis, solar fuel synthesis, dye-sensitized solar cells (DSCs), and perovskite solar cells (PSCs) are summarized, and the synthesis-component-structure-property relationship in nanoporous TiO2 spheres is highlighted. Finally, perspectives in this rapidly developing field are offered.

中文翻译：

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具有定制纹理特性的纳米多孔 TiO2 球体：可控合成、形成机制和光化学应用

摘要 纳米多孔 TiO2 球体是最近出现的一类用于光化学应用的新型 TiO2 纳米材料。与传统的 TiO2 纳米粒子相比，由低维纳米微晶组成的球形组件在结构各向同性、单分散性、纳米和（亚）微米尺度上的结构多样性、结构稳定性、光收集性能、互连纳米构建块方面具有显着优势晶界少，易回收。在光电催化和光伏领域已经证明了其优越的性能。研究工作致力于合理设计合成策略，以方便制备纳米多孔 TiO2 球体。过去十年见证了为优化光化学应用而开发纳米多孔 TiO2 球体合成策略的快速进展。化学和物理途径都得到了广泛的开发，旨在简化对纳米结构单元自组装的控制，从而控制纳米多孔 TiO2 球体的结构特性和物理化学性能。在这篇综述中，首先全面描述了不同的合成策略，特别强调了形成机制，特别是纳米微晶自组装成球形结构的途径。还讨论了显着的实验参数，用于可重复和可控地制备具有明确分级结构的纳米多孔 TiO2 球体，从组装的纳米结构块中获得可调节的多孔微结构，以及最佳的物理化学性质。总结了在环境光催化、太阳能燃料合成、染料敏化太阳能电池 (DSC) 和钙钛矿太阳能电池 (PSC) 中的重要应用，并强调了纳米多孔 TiO2 球体中的合成-组分-结构-性能关系。最后，提供了这个快速发展领域的观点。