Photocatalysis promises a solution to challenges associated with the intermittent nature of sunlight which is considered as renewable and ultimate energy source to power activities on Earth. This review aims to provide a broad overview of the field. Insight into natural photosynthesis is discussed first, which provides a scientific basis for most efforts on photocatalysis. Afterwards, the details of four existing types of photocatalysis are presented, namely photosynthesis by plants, photosynthesis by microalgae, photocatalysis by suspension and photoelectrocatalysis. Detailed analyses of simple photocatalysts and integrated photocatalytic systems are followed to shed light on the different functionalities of different components in a working photocatalyst. Special attention is given to the roles played by surface and interface chemical phenomena. Lastly, perspectives on artificial photosynthesis are discussed briefly at the end.

Two-dimensional materials are of current great interest for their promising applications to postsilicon microelectronics. Here we study, using first-principles calculations and a Monte Carlo simulation, the electronic structure and magnetism of CrI3 monolayer, whose bulk material is an interesting layered ferromagnetic (FM) semiconductor. Our results show that CrI3 monolayer remains FM with TC ∼ 75 K, and the FM order is due to a superexchange in the near-90 • Cr-I-Cr bonds. Moreover, we find that an itinerant magnetism could be introduced by carriers doping. Both electron doping and hole doping would render CrI3 monolayer half-metallic, and steadily enhance the FM stability. In particular, hole doping is three times as fast as electron doping in increasing TC, and a room temperature FM half-metallicity could be achieved in CrI3 monolayer via a half-hole doping. Therefore, CrI3 monolayer would be an appealing two-dimensional spintronic material.

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We successfully grew the high-quality single crystal of Rb0.78Fe2Se1.78, which shows sharp super-conducting transition in magnetic susceptibility and electrical resistivity. Resistivity measurements show the onset superconducting transition (Tc) at 32.1 K and zero resistivity at 30 K. From the low-temperature iso-magnetic-field magnetoresistance, large upper critical field Hc2(0) has been estimated as high as 180 T for in-plane field and 59 T for out-of-plane field. The anisotropy H ab c2 (0)/H c c2 (0) is around 3.0, right lying between those observed in KxFe2Se2 and CsxFe2Se2.

Heterogeneous catalysts with atomically defined active centers hold great promise for high-performance applications. Among them, catalysts featuring active moieties with more than one metal atom are important for chemical reactions that require synergistic effects but are rarer than single atom catalysts (SACs). The difficulty in synthesizing such catalysts has been a key challenge. Recent progress in preparing dinuclear heterogeneous catalysts (DHCs) from homogeneous molecular precursors has provided an effective route to address this challenge. Nevertheless, only side-on bound DHCs, where both metal atoms are affixed to the supporting substrate, have been reported. The competing end-on binding mode, where only one metal atom is attached to the substrate and the other metal atom is dangling, has been missing. Here, we report the first observation that end-on binding is indeed possible for Ir DHCs supported on WO3. Unambiguous evidence supporting the binding mode was obtained by in situ diffuse reflectance infrared Fourier transform spectroscopy and high-angle annular dark-field scanning transmission electron microscopy. Density functional theory calculations provide additional support for the binding mode, as well as insights into how end-on bound DHCs may be beneficial for solar water oxidation reactions. The results have important implications for future studies of highly effective heterogeneous catalysts for complex chemical reactions.

Epitaxial growth of Co on GaAs͑001͒ and its in-plane magnetic anisotropy are studied using reflection high-energy electron diffraction, a high-resolution transmission electron microscope, and the magneto-optical Kerr effect. In the initial and final stages of growth, Co exists in single-crystalline body-centered-cubic ͑bcc͒ and hexagonal-closed-packed ͑hcp͒ phases, respectively, while in the middle stage the coexistence of the bcc and hcp structures is observed. For the bcc Co thin films on GaAs͑001͒, a fourfold in-plane magnetic anisotropy with easy axes along the ͗100͘ directions is realized and discussed. ͓S0163-1829͑98͒04915-7͔The 3d transition metals exist in a variety of crystallographic and magnetic phases. Thin-film growth of these materials on crystalline substrates allows the forces present at the interface to drive the film into specific crystalline structures. These structures may be in a thermodynamically stable phase, a known high-pressure or high-temperature phase, or even a phase not previously observed. They greatly increase the variety of magnetic materials by essentially making ''new'' materials from ''old'' elements. 1The epitaxial growth of Co films serves as a good example. It is known that the hexagonal-close-packed ͑hcp͒ and face-centered-cubic ͑fcc͒ structures are, respectively, stable and metastable phases of Co. The body-centered-cubic ͑bcc͒ structure, which does not occur in nature, was realized by Prinz with epitaxial growth on a GaAs͑110͒ substrate. However, it was later pointed out by Liu and Singh that bcc Co is not a true metastable phase but a force-induced phase. 3The in-plane magnetic anisotropy of such a bcc Co thin film on GaAs͑110͒ was further determined and a negative value for the cubic anisotropy constant K 1 was proposed.2 If this were true, a fourfold in-plane magnetic anisotropy with easy axes along the ͗110͘ direction would then be expected in the bcc Co films on GaAs͑001͒ substrates. In fact, a fourfold in-plane magnetic anisotropy with the easy axes along the ͗100͘ rather than the ͗110͘ direction was observed by Blundell et al. 4 Interestingly, it was later argued by Gu et al. that Co films grown on GaAs͑001͒ were actually not bodycentered cubic but two-domain hexagonal close packed by which the fourfold magnetic anisotropy along the ͗100͘ direction could be explained by such a microstructure.5 Obviously, the epitaxial structure of Co on GaAs͑001͒ and its magnetic anisotropy are still very controversial. In this work, we present a clear picture of the epitaxial growth of Co on GaAs͑001͒, which clears up the previous controversy about the structure of Co thin films on GaAs͑001͒. With the help of this clear picture, we prove that the bcc Co films on GaAs͑001͒ show a fourfold in-plane magnetic anisotropy.Co films were grown in a molecular-beam epitaxy ͑MBE͒ growth chamber connected with the VG-ESCALAB-5 electron spectrometer system. The Te-doped GaAs͑001͒ singlecrystal wafers were polished and treated by ordinary device cleaning process. The final substrate cleaning w...

The hierarchical CoO microflower film prepared by a low-temperature solvothermal method shows excellent electrochemical lithium/sodium storage performances.

Hierarchically nanostructured binary/multiple transition-metal oxides with electrically conductive coatings are very attractive for lithium-ion batteries owing to their excellent electrochemical properties induced by their unique compositions and microstructures. Herein, hierarchical MnO-doped FeO@C composite nanospheres are prepared by a simple one-step annealing in Ar atmosphere, using Mn-doped Fe-based metal-organic frameworks (Mn-doped MIL-53(Fe)) as precursor. The MnO-doped FeO@C composite particles have a uniform nanosphere structure with a diameter of ∼100 nm, and each nanosphere is composed of clustered primary nanoparticles with an amorphous carbon shell, forming a unique hierarchical nanoarchitecture. The as-prepared hierarchical MnO-doped FeO@C composite nanospheres exhibit markedly enhanced lithium-storage performance, with a large capacity of 1297.5 mAh g after 200 cycles at 200 mA g. The cycling performance is clarified through analyzing the galvanostatic discharge/charge voltage profiles and electrochemical impedance spectra at different cycles. The unique microstructures and Mn element doping of the hierarchical MnO-doped FeO@C composite nanospheres lead to their enhanced lithium-storage performance.