No abstract

Titanium dioxide is the only known material that can enable gas-phase CO 2 photocatalysis in its anatase and rutile polymorphic forms. Materials engineering of polymorphism provides a useful strategy for optimizing the performance metrics of a photocatalyst. In this paper, it is shown that the less well known rhombohedral polymorph of indium sesquioxide, like its well-documented cubic polymorph, is a CO 2 hydrogenation photocatalyst for the production of CH 3 OH and CO. Significantly, the rhombohedral polymorph exhibits higher activity, superior stability and improved selectivity towards CH 3 OH over CO. These gains in catalyst performance originate in the enhanced acidity and basicity of surface frustrated Lewis pairs in the rhombohedral form.

No abstract

Emerging two-dimensional (2D) semiconducting materials serve as promising alternatives for next-generation digital electronics and optoelectronics. However, large-scale 2D semiconductor films synthesized so far are typically polycrystalline with defective grain boundaries that could degrade their performance. Here, for the first time, wafer-size growth of a single-crystal Bi 2 O 2 Se film, which is a novel air-stable 2D semiconductor with high mobility, was achieved on insulating perovskite oxide substrates [SrTiO 3 , LaAlO 3 , (La, Sr)(Al, Ta)O 3 ]. The layered Bi 2 O 2 Se epilayer exhibits perfect lattice matching and strong interaction with perovskite oxide substrates, which enable unidirectional alignment and seamless mergence of multiple seeds into single-crystal continuous films free of detrimental grain boundaries. The single-crystal Bi 2 O 2 Se thin films show excellent spatial homogeneity over the entire wafer and allow for the batch fabrication of high-performance field-effect devices with high mobilities of ∼150 cm 2 V −1 s −1 at room temperature, excellent switching behavior with large on/off ratio of >10 5 , and high drive current of ∼45 μA μm −1 at a channel length of ∼5 μm. Our work makes a step toward the practical applications of high-mobility semiconducting 2D layered materials and provides an alternative platform of oxide heterostructure to investigate novel physical phenomena.

A highly efficient and environmentally-friendly oxidation process is always desirable for air purification. This study reported a novel carbon quantum dots (CQDs)/ZnFeO composite photocatalyst for the first time through a facile hydrothermal process. The CQDs/ZnFeO (15 vol %) composite demonstrates stronger transient photocurrent response, approximately 8 times higher than that of ZnFeO, indicating superior transfer efficiency of photogenerated electrons and separation efficiency of photogenerated electron-hole pairs. Compared with pristine ZnFeO nanoparticles, CQDs/ZnFeO displayed enhanced photocatalytic activities on gaseous NO removal and high selectivity for nitrate formation under visible light (λ > 420 nm) irradiation. Electron spin resonance analysis and a series of radical-trapping experiments showed that the reactive species contributing to NO elimination were ·O and ·OH radicals. The possible mechanisms were proposed regarding how CQDs improve the photocatalytic performance of ZnFeO. The CQDs are believed to act as an electron reservoir and transporter as well as a powerful energy-transfer component during the photocatalysis processes over CQDs/ZnFeO samples. Furthermore, the toxicity assessment authenticated good biocompatibility and low cytotoxity of CQDs/ZnFeO. The results of this study indicate that CQDs/ZnFeO is a promising photocatalyst for air purification.

Titanium nitride halide TiNX (X = F, Cl, Br) monolayers for highly efficient excitonic solar cells.

The photoexcitation dynamics plays a key role in determining the properties of van der Waals heterostructures (vdWHs). Based on the time-dependent density functional theory combined with nonadiabatic molecular dynamics, we investigate the charge transfer in Janus-MoSSe/WS vdWHs. Ultrafast charge separation is observed, arising from the large overlapping between the donor and acceptor states. While the electron-hole recombination is 2 orders of magnitude slower than the charge separation, this can be understood by the fact that the initial and final states are strictly confined to different materials. Additionally, photoresponsivity performance of the vdWHs is also evaluated using density functional theory combined with the nonequilibrium Green's functions. Simulated results of high photoresponsivity in a broad range of the spectrum endows proposed systems powerful potential in optoelectronic and photovoltaic applications. The atomistic picture revealed in our work provides chemical guidelines and facilitates the design of next-generation devices for light detecting and harvesting.

Activated carbon fibers with high micropore volume and large specific surface area were prepared from abundant and low-cost coconut fibers, which show excellent adsorption performances towards various dyes.