Hydrous TiO₂ colloidal spheres (HTCS) derived from the direct precipitation of titanium alkoxides have attracted continuous interests since 1982. Entering the 21st century, rapid progress in the development of structure-directing agents (SDAs) have enabled reproducible and size-controllable synthesis of highly uniform HTCS with diameters in the nano- to micro-meter range. The availability of various HTCS provides versatile self-templating platforms for the targeted synthesis of nanoporous TiO₂ and titanate spheres with tunable composition, crystallographic phases, and internal structures for a variety of advanced photo/electrochemical applications. This review provides a historical overview for the evolution of HTCS, along with an insightful discussion for the formation mechanism of self-assembly of HTCS during the sol-gel process. Key synthetic parameters including SDA, solvent, reaction temperature and water dosage are discussed for the size and morphology control of HTCS with predictable textural properties. Then, we describe the synthetic strategies of nanoporous TiO₂ and titanate spheres using various HTCS as self-templates. Here, the focus lies on the interactions between TiO₂ nanobuilding blocks with precursors or media at the solid/liquid and solid/solid interfaces, the concurrent phase transitions, and the microstructural and morphological evolutions. Selective formation of crystal phase and internal structures (e.g., solid, hollow, core-shell, yolk-shell) are discussed by manipulating the crystallization kinetics. To further elucidate the composition-structure-property-performance relationship for the resulting nanoporous TiO₂ and titanate spheres, their applications in photo(electro)catalysis, mesoscopic solar cells, and lithium-ion batteries are scrutinized. Finally, we share opinions on key challenges and perspectives for the future controllable preparation, formation mechanisms, and applications of HTCS and their crystalline derivatives.

自 1982 年以来，由钛醇盐直接沉淀得到的含水 TiO ₂胶体球 (HTCS) 一直引起人们的兴趣。进入 21 世纪，结构导向剂 (SDA) 的快速发展使得可重复和尺寸可控的合成成为可能。直径在纳米到微米范围内的高度均匀的 HTCS。各种 HTCS 的可用性为纳米多孔 TiO ₂的靶向合成提供了通用的自模板平台和具有可调成分、结晶相和内部结构的钛酸盐球体，适用于各种先进的光/电化学应用。这篇综述提供了 HTCS 演变的历史概述，并对溶胶-凝胶过程中 HTCS 自组装的形成机制进行了深入的讨论。讨论了包括 SDA、溶剂、反应温度和水剂量在内的关键合成参数，用于控制具有可预测纹理特性的 HTCS 的尺寸和形态。然后，我们描述了使用各种 HTCS 作为自模板的纳米多孔 TiO ₂和钛酸盐球的合成策略。这里，重点在于 TiO ₂之间的相互作用在固/液和固/固界面上具有前体或介质的纳米结构单元、同时发生的相变以及微观结构和形态演变。通过操纵结晶动力学讨论了晶相和内部结构（例如，实心、空心、核-壳、蛋黄-壳）的选择性形成。为了进一步阐明所得纳米多孔 TiO ₂和钛酸盐球体的组成-结构-性能-性能关系，详细研究了它们在光（电）催化、介观太阳能电池和锂离子电池中的应用。最后，我们就HTCS及其结晶衍生物的未来可控制备、形成机制和应用的关键挑战和前景分享了看法。