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Two‐dimensional (2D) materials possess special physical and chemical properties. They have been proved to have potential application advantage in the microwave absorption (MA) and electromagnetic interference (EMI) shielding. Particularly, they exhibit positive shielding and absorbing response to EMI. Here, the research progress of preparation, electromagnetic performance and microwave shielding/absorbing mechanisms of 2D composite materials are introduced. Effective preparation routes including introducing heteroatoms, constructing unique structures and 2D composite materials are described. Furthermore, the application prospects and challenges for the development of novel EMI materials are expatiated. [ABSTRACT FROM AUTHOR]

The production of hydrogen via electrochemical water splitting has the potential to enable the utilization of hydrogen‐powered fuel cells on a large scale. However, to realize this technology, inexpensive, noble metal‐free electrocatalysts possessing high performances for the hydrogen evolution reaction (HER) are needed. Mo2C nanoparticles recently receive much attention as alternative noble metal‐free electrocatalysts because their electronic structures are akin to that of Pt. However, the synthesis of Mo2C at nanoscale with high catalytic activity for HER remains a great challenge. Moreover, although efforts have been made to prevent their aggregation, the particles coalesce during high temperature carbonization, which is typically used to produce such transition metal carbides. Here, the synthesis of Mo2C nanodots that are well‐dispersed within 3D cage‐like carbon microparticles using rationally designed Mo‐based xerogels, which are prepared via the sol–gel process as precursors, is reported. During their pyrolysis, the xerogels maintain their structures while the Mo species in them transform into well‐dispersed Mo2C nanodots in situ. The as‐synthesized Mo2C nanodots exhibit excellent electrocatalytic activity for HER, in both alkaline and acidic media, while remaining largely stable. The work also demonstrates a promising synthetic route and procedure to other well‐dispersed yet stable nanocatalysts. [ABSTRACT FROM AUTHOR]

Molybdenum carbide possessing a Pt‐like d‐band electronic structure is considered as one of potential candidates of electrocatalysts and it shows intrinsic catalytic property. However, a high carbonizing temperature easily leads to the coalescence of nanoparticles (NPs). Here, we propose a simple sol‐gel route to achieve high dispersity of carbide NPs by designing a Mo‐involved xerogel. The results show that molybdenum carbide NPs are dispersed and anchored on the nitrogen‐doped carbon nanosheets (Mo2C@NC). Ultrathin carbon layers resemble graphene and the network structures act as a support of carbide NPs, which can hinder NPs' coalescence effectively. Nanpoparticles cross‐coupled on network‐structure nanosheets display the grid shapes. Electrochemical studies indicate that Mo2C@NC material exhibits outstanding hydrogen evolution performance in alkaline electrolyte. [ABSTRACT FROM AUTHOR]

Porous Graphitic carbon nitride(pg‐C3N4) possessing hierarchical pores and lamellar nanostrucutres was synthesized in the absent of templates by pyrolysis of the solution‐assisted mixing dual‐precursors. The samples were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 porosimeter, X‐ray photoelectron spectroscopy, UV‐Vis andphotoluminescence spectroscopy.The photocatalytic activities of as‐prepared materials for degradation of methyl violet were studied. The results show that the as‐prepared g‐C3N4consists of well‐dispersed layers with uniform sizeand hierarchical (Meso/Macro) pores in the nanosheets, which favor photogenerated electron‐hole pairs'separation, and the degradation of methyl violet conforms to the quasi‐first‐order kinetic model. The porous g‐C3N4 synthesized by optimizing precursors' ratios exhibited faster degradation rate than g‐CN material in the process of photocatalyzing methyl violet andthe degradation rate was over 93 % after irradiation of 180 min, implying that the as‐prepared hierarchically porous g‐C3N4 is a high‐effective and metal‐free photocatalytic material for degradation of pollutants. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting has been considered as a promising method for large‐scale hydrogen production. However, the development of high‐performance and low‐cost noble metal‐free electrocatalysts for hydrogen evolution reaction (HER) remains a great challenge. Transition metal carbides (such as molybdenum carbide) are one of the most potential substitutes for noble metal as electrocatalysts for HER. One of the effective measures for further enhancing their performances is to hinder the coalescence of nanoparticles. Here we demonstrate a two‐dimensional ultrafine molybdenum carbide‐coupled mesoporous structured meshlike carbon nanolayers synthesized vis facile route based on holes in the carbon nanolayer structures blocking nanoparticle agglomeration. Molybdenum carbide clusters dispersed on the carbon nanolayers are successfully prepared by carbonization of molybdate‐polyvinylpyrrolidone precursor as a proof of concept, which exhibits excellent electrocatalytic activity for the HER and high stability in basic medium. The present study provides some references for the design and synthesis of nanostructured electrocatalysts utilizing 2D meshlike materials to prevent nanoparticles from agglomerating. [ABSTRACT FROM AUTHOR]

Transition metal carbide such as molybdenum carbide is most potential alternative to Pt catalysts for the hydrogen evolution reaction (HER). A high effective non‐noble metal electrocatalyst synthesized by the facile route isurgently needed. Herein, we designed a facile approach to synthesize molybdenum carbide nanocrystal dispersed on hexagonal carbon nanotablets possessing mesoporous structures. The electrocatalytic activities for HER were studied. The results show that as‐synthesized molybdenum carbide nanocomposites exhibit a superior HER activity and stability, with an overpotential of 176 mV to drive j=10 mA cm−2 in basic solution and a smaller Tafel slope of 52 mV dec−1in acidic medium, implying molybdenum carbide hexagonal nanotablets have a promising application as Pt‐free electrocatalysts for HER. This strategy also opens a new way to fast synthesize other non‐noble metal electrocatalysts for various applications. [ABSTRACT FROM AUTHOR]

Distinct three-dimensional hierarchically stacking SnO2-Sb/TiO2-NTs electrode with a good-adhesion TiO2-NTs@SnO2-Sb interlayer, a compact plate SnO2-Sb middle layer, and an apparent uniform microsphere layer was successfully prepared through the hydrothermal method. The evolution of micro-morphology and structure of electrode catalyst layer was realized so as to improve the catalytic performance of electrode through tuning the hydrochloric acid concentration. Experimental results show that SnO2-Sb/TiO2-NTs electrode prepared in 0.5 mol L−1 HCl condition possesses the optimal performance containing a low phenol oxidation potential of 1.2 V (vs. SCE), and a maximum current density of 3.8 mA cm−2 towards phenol degradation in phosphate buffered solution. The electrochemical phenol removal results show that the phenol degradation process coincides with the first-order kinetics and the corresponding optimal constant reaches 14.2 × 10−3 min−1. The TOC removal efficiency of optimal electrode reaches 62%. Graphical abstract The evolution of micro-morphology and structure of electrode was realized through tuning the hydrochloric acid concentration so as to improve the catalytic performance of electrode. [ABSTRACT FROM AUTHOR]

Summary: This study has developed a predictive model for the cross‐contamination of pork by Listeria monocytogenes during bowl chopping. The transfer rates of L. monocytogenes were measured in sixteen chopping scenarios based on practical work. Meanwhile, contaminated bowl chopper was cleaned with either a dry rag (DR), warm water (WW) or 70% ethanol + water (EW), respectively. It was showed that significant differences (P < 0.05) were observed among the three cleaning methods on the reduction of L. monocytogenes, the greatest log reduction being achieved by EW. Moreover, the model introduced by a previous study, predicting cross‐contamination of L. monocytogenes during meat slicing, was improved and validated in this study. Verification results showed that the improved model was acceptable for predicting L. monocytogenes cross‐contamination during pork chopping with coefficients of determination (R2 > 0.82), accuracy factors (Af < 1.44), bias factors (Bf < 1.42), and root mean square error (RMSE < 0.99). Furthermore, the modified model might provide an effective tool for assessing the risk of the cross‐contamination of meat products. [ABSTRACT FROM AUTHOR]