Loading a noble metal on Bi₄Ti₃O₁₂ could enable the formation of the Schottky barrier at the interface between the former and the latter, which causes electrons to be trapped and inhibits the recombination of photoelectrons and photoholes. In this paper, AgPt/Bi₄Ti₃O₁₂ composite photocatalysts were prepared using the photoreduction method, and the effects of the type and content of noble metal on the photocatalytic performance of the catalysts were investigated. The photocatalytic degradation of rhodamine B (RhB) showed that the loading of AgPt bimetallic nanoparticles significantly improved the catalytic performance of Bi₄Ti₃O₁₂. When 0.10 wt% noble metal was loaded, the degradation rate for RhB of Ag_0.7Pt_0.3/Bi₄Ti₃O₁₂ was 0.027 min⁻¹, which was respectively about 2, 1.7 and 3.7 times as that of Ag/Bi₄Ti₃O₁₂, Pt/Bi₃Ti₄O₁₂ and Bi₄Ti₃O_12. The reasons may be attributed as follows: (i) the utilization of visible light was enhanced due to the surface plasmon resonance effect of Ag and Pt in the visible region; (ii) Ag nanoparticles mainly acted as electron acceptors to restrain the recombination of photogenerated electron-hole pairs under visible light irradiation; and (iii) Pt nanoparticles acted as electron cocatalysts to further suppress the recombination of photogenerated electron-hole pairs. The photocatalytic performance of Ag_0.7Pt_0.3/Bi₄Ti₃O₁₂ was superior to that of Ag/Bi₄Ti₃O₁₂ and Pt/Bi₃Ti₄O₁₂ owing to the synergistic effect between Ag and Pt nanoparticles.

Hierarchical micro-/mesoporous graphitic carbon spheres (HGCS) with a uniform diameter of ~0.35 μm were synthesized by Fe-catalyzed graphitization of amorphous carbon spheres resultant from hydrothermal carbonization. The HGCS resultant from 3 h at 900 °C with 1.0 wt % Fe catalyst had a high graphitization degree and surface area as high as 564 m²/g. They also exhibited high specific capacitance of 140 F/g at 0.2 A/g and good electrochemical stability with 94% capacitance retention after consecutive 2500 cycles. The graphitization degree of the HGCS contributed to 60% of their specific capacitance, and their specific capacitance per unit surface area was as high as 0.2 F/m², which was much higher than in the most cases of porous amorphous carbon materials reported before. In addition, the HGCS showed a high adsorption capacity of 182.8 mg/g for methylene blue (MB), which was 12 times as high as that in the case of carbon spheres before graphitization.

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined.