Yali Zheng

Ultrathin mesoporous Co3O4 nanosheets with excellent photo-/thermo-catalytic activity

Ultrathin mesoporous Co3O4 nanosheets on a stainless steel mesh (SS–Co3O4) have been synthesized through an electrochemical deposition method. The SS–Co3O4 catalyst exhibits high photothermal performance, resulting in a considerable increase of temperature above the light-off temperature for VOC oxidation. Aerobic oxidations of propylene and propane under simulated sunlight were selected as probe reactions to explore the photo-/thermo-catalytic (PTC) activity. The results show that SS–Co3O4 with only 7 mg of Co3O4 grown on the substrate possesses superior PTC activity, which merely occurs around the directly grown SS–Co3O4 rather than the Co3O4 coated SS. The combined properties of SS–Co3O4 such as the ultrathin two-dimensional shape, foam-like porous inside architecture, and supported metal substrate could lead to the integrative advantages of the maximum utilization of photothermal conversion, more catalytically active sites, and enhanced amount and mobility of surface lattice oxygen species, resulting in excellent PTC activity of SS–Co3O4. This work provides insights into the rational design of monolith catalysts for the solar driven environmental purification and suggests new ideas toward the overall utilization of solar energy.

Surfactant-free hydrothermal fabrication of monoclinic BiVO4 photocatalyst with oxygen vacancies by copper doping

Poor electron transport leads to the high recombination of photogenerated charge carriers for photocatalysts, which limits the photocatalytic performance. In order to improve charge transport properties, Cu doped BiVO4(Cu–BiVO4) was prepared by a facile hydrothermal method. The doped material provided a maximal photocurrent of 10 μA cm−2 at +0.4 V vs. SCE, which was 5 times higher than the undoped one. The result implied much improvement for the separation of the carriers for Cu–BiVO4, which attributed to the suitable amount of oxygen vacancies as positive charge centers caused by doping. Oxygen vacancies trapped photogenerated electrons and thus inhibited the electrons–holes recombination. The photocatalytic degradation of rhodamine B (RhB) was used to evaluate the photoactivity of the materials. The results showed that the photocatalytic properties of the doped materials were evidently higher than the undoped BiVO4. The photocatalytic reaction mechanism is also discussed in this article, and the superoxide radical was confirmed to be the main active species for the photocatalytic degradation process.

Bi2WO6 quantum dot-intercalated ultrathin montmorillonite nanostructure and its enhanced photocatalytic performance

The kinetic competition between electron-hole recombination and water oxidation is a key limitation for the development of efficient solar water splitting materials. In this study, we present a solution for solving this challenge by constructing a quantum dot-intercalated nanostructure. For the first time, we show the interlayer charge of the intercalated nanostructure can significantly inhibit the electron-hole recombination in photocatalysis. For Bi2WO6 quantum dots (QDs) intercalated in a montmorillonite (MMT) nanostructure as an example, the average lifetime of the photogenerated charge carriers was increased from 3.06 μs to 18.8 μs by constructing the intercalated nanostructure. The increased lifetime markedly improved the photocatalytic performance of Bi2WO6 both in solar water oxidation and environmental purification. This work not only provides a method to produce QD-intercalated ultrathin nanostructures but also a general route to design efficient semiconductor-based photoconversion materials for solar fuel generation and environmental purification.