TiO₂ photocatalyst has attracted great interest owing to its wide applications in environmental cleaning and new energy production. Both the composition and the structure modifications affect its photocatalytic performances. Herein, we report the design of various TiO₂-hybrid nanomaterials like TiO₂ doped by CdS, CdSe, C₃N₄, Au, and Ag quantum dots with low band-gap. They exhibit high activity during photocatalytic/photoelectrocatalytic degradation of organic pollutants, H₂ evolution from water splitting, and CO₂ conversion by using sunlight. Meanwhile, the potential application of the photo-driven dual electrodes (Z-mechanism systems) in photocatalytic fuel cell (PEC) has been explored. Furthermore, better photocatalysts served as coating layer for electrodes through composition- and structure-engineering have been developed.