Controllable design of natural gully-like TiO2–ZrO2 composites and their photocatalytic degradation and hydrogen production by water splitting

Using polystyrene (PS) spheres as self-assembling templates, a series of natural gully-like TiO2–ZrO2 nanocomposites were prepared using instant centrifugation with one-step hydrolysis in combination with a vacuum and calcination post-processing method. XRD, UV-vis/DRS, XPS, SEM, and N2 adsorption–desorption measurements are employed to analyze and characterize the composition, structure, and morphology of the gully-like TiO2–ZrO2 composites. The results show that this series of TiO2–ZrO2 composite materials have an obvious gully structure, and the gully distribution is uniform. Imitating the formation process of natural ravines, the friction and adhesion between the PS spheres and the TiO2–ZrO2 nanoparticles could be changed by adjusting the reactant ratio. In the meantime, the water in the reaction system continuously flushes the formed loose cover, resulting in a cross-section or a fault with different shapes. Increasing the reaction time or accelerating the stirring speed can be beneficial for the formation of three-dimensional gully erosion, resulting in samples with different gully widths, which provides a new approach for the design of samples with controllable morphology. In this paper, the prepared gully-like TiO2–ZrO2 composites show a high specific surface area and a smaller band gap. We prepared a sample using titanium isopropoxide and n-butoxy polyethylene zirconium with the precursor volume ratio being about 1 : 0.25 (TZ 1 : 0.25), which shows excellent photocatalytic performance under UV light and simulated sunlight, and presents the ability to degrade organic pollutants with different structures. In addition, the cumulative H2 evolution quantity, which the sample (TZ 1 : 4) brings out via photocatalytic H2 evolution from water splitting under 8 h light irradiation, reaches 97.1 μmol g−1, indicating that the sample has the capacity of photocatalytic water splitting into hydrogen. Furthermore, a trapping experiment was performed, indicating that the active radicals ˙O2−, h+, and ˙OH− are responsible for the photocatalytic reaction, and the possible reaction mechanism of gully-like TiO2–ZrO2 in both photocatalytic degradation and photocatalytic H2 evolution from water splitting is also proposed.