Design and synthesis of multistructured three-dimensionally ordered macroporous composite bismuth oxide/zirconia: Photocatalytic degradation and hydrogen production.

Two types of three-dimensionally ordered macroporous (3DOM) Bi2O3/ZrO2 composites were prepared by the sol-gel method combined with the decompression filling method using polystyrene (PS) microspheres and EO20PO70EO20 (P123) as the templates. The crystal structure, morphology, and surface physicochemical properties of Bi2O3/ZrO2 composites were well characterized by X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and N2 adsorption-desorption measurements. The results show that 3DOM Bi2O3/ZrO2 composites possessed mixed crystal phases including the monoclinic bismuth oxide and mixed zirconia phases, and moreover exhibited a regular arrangement and pure tetragonal (or hexagonal) macroporous structure. Moreover, compared to Bi2O3/ZrO2, the specific surface areas of 3DOM Bi2O3/ZrO2 composites were ca. 2.7-2.8 times. In addition, the properties of 3DOM Bi2O3/ZrO2 composites with the tetragonal "fishing net" and hexagonal "honeycomb" structure were compared, and the relationship between the structure and activity of 3DOM Bi2O3/ZrO2 composites was determined. The results show that in the UV photocatalytic degradation of pollutants and splitting of water into hydrogen using 3DOM Bi2O3/ZrO2 composite, the tetragonal "fishing net" structure exhibited better activity than the hexagonal "honeycomb" structure. This can be attributed to different photocatalytic properties of the composites with different structures (tetragonal "fishing net" and hexagonal "honeycomb" structures).