Search

Rechargeable aqueous zinc ion batteries (AZIBs) have gained considerable attention owing to their low cost and high safety, but dendrite growth, low plating/stripping efficiency, surface passivation, and self-erosion of the Zn metal anode are hindering their application. Herein, a one-step in situmolecular engineering strategy for the simultaneous construction of hierarchical MoS2double-layer nanotubes (MoS2-DLTs) with expanded layer-spacing, oxygen doping, structural defects, and an abundant 1T-phase is proposed, which are designed as an intercalation-type anode for “rocking-chair” AZIBs, avoiding the Zn anode issues and therefore displaying a long cycling life. Benefiting from the structural optimization and molecular engineering, the Zn2+diffusion efficiency and interface reaction kinetics of MoS2-DLTs are enhanced. When coupled with a homemade ZnMn2O4cathode, the assembled MoS2-DLTs//ZnMn2O4full battery exhibited impressive cycling stability with a capacity retention of 86.6% over 10 000 cycles under 1 A g–1anode, outperforming most of the reported “rocking-chair” AZIBs. The Zn2+/H+cointercalation mechanism of MoS2-DLTs is investigated by synchrotron in situpowder X-ray diffraction and multiple ex situcharacterizations. This research demonstrates the feasibility of MoS2for Zn-storage anodes that can be used to construct reliable aqueous full batteries.

The hydrogen evolution reaction (HER) is a half-cell reaction in water electrolysis for producing hydrogen gas. In industrial water electrolysis, the HER is often conducted in alkaline media to achieve higher stability of the electrode materials. However, the kinetics of the HER in alkaline medium is slow relative to that in acid because of the low concentration of protons in the former. Under the latter conditions, the entire HER process will require additional effort to obtain protons by water dissociation near or on the catalyst surface. Heterostructured catalysts, with fascinating synergistic effects derived from their heterogeneous interfaces, can provide multiple functional sites for the overall reaction process. At present, the activity of the most active known heterostructured catalysts surpasses (platinum-based heterostructures) or approaches (noble-metal-free heterostructures) that of the commercial Pt/C catalyst under alkaline conditions, demonstrating an infusive potential to break through the bottlenecks. This review summarizes the most representative and recent heterostructured HER catalysts for alkaline medium. The basics and principles of the HER under alkaline conditions are first introduced, followed by a discussion of the latest advances in heterostructured catalysts with/without noble-metal-based heterostructures. Special focus is placed on approaches for enhancing the reaction rate by accelerating the Volmer step. This review aims to provide an overview of the current developments in alkaline HER catalysts, as well as the design principles for the future development of heterostructured nano- or micro-sized electrocatalysts.

In this paper, a simple thermal decomposition synthesis route for a carbon–nitrogen–sulfur (C–N–S) co-doped titanium dioxide (TiO2) mischcrystal with an isobandgap property for visible light applications using urea as the C, and N source and titanium(iv) sulfate [Ti(SO4)2] as S source is reported. The C–N–S co-doped TiO2mischcrystal exhibited a unique isobandgap characteristic and prominent red-shift in the ultraviolet-visible absorption spectrum and a much narrower band gap (2.42 eV and 1.39 eV) because of defects and impurity levels which were confirmed using powder X-ray diffraction, diffuse reflectance spectroscopy (DRS), photoluminescence, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The excellent photocatalytic performance of the C–N–S co-doped TiO2mischcrystal samples was demonstrated using degradation of methylene blue and phenol under visible light. The apparent degradation rate of black TiO2is 4–7 times higher than that of C–N–S co-doped TiO2(anatase or rutile) under visible light irradiation. The valence band XPS and DRS results were carefully examined to understand the band gap reduction of C–N–S co-doped TiO2. This study confirms that the band gap structure of C–N–S co-doped TiO2is determined by the mixed crystalline structure and the formation of impurity levels and defective levels. A new idea is presented that will be useful for the design of band gap structure for photocatalysts with higher photocatalytic activities under visible light irradiation.

Abstract

Three types of hollow urchinlike α-MnO2nanostructures, namely, columnar nanorod clusters, tetragonal nanotube clusters, and tetragonal nanorod clusters, have been synthesized through a facile hydrothermal method. The microstructure and morphologies of the resulting materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction, and the microwave absorption properties of these nanostructures were investigated in terms of complex permittivity and permeability. The results indicate an obvious magnetic loss in the manganese oxide/paraffin wax composites. The tetragonal nanorod clusters exhibit enhanced microwave absorption properties compared with columnar nanorod clusters and tetragonal nanotube clusters, which result from proper electromagnetic impedance matching. These urchinlike manganese oxide nanostructures are considered to have great potential applications as microwave absorbents.