Compared with the nitrogen doped in the solid TiO2 sphere,the nitrogen concentration in the mesoporous TiO2 sphere is much higher, which increases from 0.17% to 1.31% (Fig. 8). In the preparation process, the CTAB is filled in the interstice of TiO2nanocrystals,which makes the stacked nanocrystals become fluffy (Scheme 1).The loose packing structure is in favor of the further filling of ammonia in the interstice of TiO2nanocrystals. Every TiO2 nanocrystal is surrounded with ammonia molecules, and the nitrogen is introduced into every TiO2 nanocrystal lattice by the hydrothermal and calcination treatment. To every TiO2 nanocrystal, the nitrogen doping is heterogeneous, but to the whole mesoporous TiO2sphere, the nitrogen doping is homogeneous. Amass of heterogeneous N doped TiO2nanocrystals assemble intoa homogeneous N doped TiO2sphere. Compared with the solid TiO2sphere (N-p-TiO2), the contact between TiO2nanocrystals and ammonia in 0.5-N-TiO2is significantly increased, resulting in an enhanced doping concentration..