Jiangjun Xian

TiO2 nanotube array-graphene-CdS quantum dots composite film in Z-scheme with enhanced photoactivity and photostability.

The most efficient solar energy utilization is achieved in natural photosynthesis through elaborate cell membrane with many types of molecules ingeniously transferring photogenerated electrons to reactants in a manner similar to the so-called Z-scheme mechanism. However, artificial photosynthetic systems based on semiconductor nanoparticles are inevitably accompanied by undesired non-Z-scheme electron transfer and back reactions, which adversely affect the photoactivity and photostability of the systems. Herein, we report on a novel Z-scheme system with an electrochemically converted graphene (GR) film as the electron mediator interlayer contacted with both TiO2 nanotube (TNT) array and CdS quantum dots (CdS QDs) on two sides. The obtained TiO2 nanotube array-graphene-CdS quantum dots (TNT-GR-CdS) composite film shows higher photoelectric response and photocatalytic activities than other bare TNT, TNT-CdS, TNT-GR, and TNT-CdS-GR. Moreover, compared to TNT-CdS, the activity stability is significantly improved, and the residual amount of Cd element in reaction solution is reduced ∼8 times over TNT-GR-CdS. Various measurements of photoelectrochemistry and radicals reveal that the enhanced photoactivity and photostabilities of TNT-GR-CdS are due to the efficient spatial separation of the photogenerated electron-hole pairs and the restricted photocorrosion of CdS via an efficient Z-scheme mechanism under simulated sunlight.

Sn3O4: a novel heterovalent-tin photocatalyst with hierarchical 3D nanostructures under visible light

Sn3O4 with hierarchical 3D nanostructures was synthesized for the first time by a facile template-free solvothermal method. The heterovalent photocatalyst is highly efficient and stable in the degradation of azo dyes under visible light.

One-step preparation of hollow ZnO core/ZnS shell structures with enhanced photocatalytic properties

We report here a facile one-step strategy to prepare hollow ZnO core/ZnS shell structures by microwave irradiation. The growth mechanism of the hollow core/shell structures was investigated in detail. ZnO truncated hexagonal pyramids first form on as-grown precursor flakes and then evolve into ZnO hexagonal twin crystals, which subsequently grow up and dissolve internally. The hollowing progress is firstly controlled by the Kirkendall effect and then undergoes an Ostwald ripening process. Hollow structures and the formation of ZnO/ZnS heterostructure bring enhanced photocatalytic activities to ZnO core/ZnS shell structures. The formed ZnO/ZnS heterostructures also fill the surface defects of ZnO crystals and improve the stability of the photocatalysts by overcoming the photocorrosion effect of a single ZnO photocatalyst under UV light irradiation. Superoxide radicals (O˙−2) are the key active species in the photocatalytic system of degradation of p-chlorophenol over hollow ZnO core/ZnS shell structures. The photocatalysis process has been discussed and a possible mechanism also has been proposed. This work is helpful to controllably construct other hollow core/shell structures, develop ZnO-based photocatalysts without photocorrosion effect and further study the photocatalytic mechanism of similar systems.

Structuring β-Ga2O3 Photonic Crystal Photocatalyst for Efficient Degradation of Organic Pollutants

Coupling photocatalysts with photonic crystals structure is based on the unique property of photonic crystals in confining, controlling, and manipulating the incident photons. This combination enhances the light absorption in photocatalysts and thus greatly improves their photocatalytic performance. In this study, Ga2O3 photonic crystals with well-arranged skeleton structures were prepared via a dip-coating infiltration method. The positions of the electronic band absorption for Ga2O3 photonic crystals could be made to locate on the red edge, on the blue edge, and away from the edge of their photonic band gaps by changing the pore sizes of the samples, respectively. Particularly, the electronic band absorption of the Ga2O3 photonic crystal with a pore size of 135 nm was enhanced more than other samples by making it locate on the red edge of its photonic band gap, which was confirmed by the higher instantaneous photocurrent and photocatalytic activity for the degradation of various organic pollutants under ultraviolet light irradiation. Furthermore, the degradation mechanism over Ga2O3 photonic crystals was discussed. The design of Ga2O3 photonic crystals presents a prospective application of photonic crystals in photocatalysis to address light harvesting and quantum efficiency problems through manipulating photons or constructing photonic crystal structure as groundwork.

A large-area smooth graphene film on a TiO2 nanotube array via a one-step electrochemical process

A large-area smooth graphene film on a TiO2 nanotube array was directly fabricated using a simple, green and low-cost electrochemical process. The controllable formation mechanism of the graphene film is demonstrated in detail. The enhanced photoelectric and photocatalytic properties of the composite film imply great potential applications in various fields.