Heterostructured CoFeP/CoP as an Electrocatalyst for Hydrogen Evolution in Alkaline Media.

Developing highly efficient and persistent transition-metal-phosphide (TMP)-based electrocatalysts is critical for the hydrogen evolution reaction (HER) via water splitting in alkaline media. Herein, we constructed a unique heterostructured CoFeP/CoP grown on a nickle foam (NF) via hydrothermal and dipping methods followed by phosphorization at different temperatures for HER. The experimental results exhibit that the HER activity of CoFeP/CoP-400 is accelerated after the construction of heterostructures. The unique heterostructure provides plentiful active sites and a large surface area, which are beneficial for HER in 1.0 M KOH. CoFeP/CoP-400 displays a small overpotential of 78 mV at a current density of 10 mA cm-2 and a smaller Tafel slope of 55.5 mV dec-1. Moreover, CoFeP/CoP-400 shows excellent stability with a long-term operating time of 12 h. This work provides an effective method for the construction of TMPs with heterostructures for promoting energy conversion.

Design of an Internal/External Bicontinuous Conductive Network for High-Performance Asymmetrical Supercapacitors.

High-energy density supercapacitors have attracted extensive attention due to their electrode structure design. A synergistic effect related to core-shell structure can improve the energy storage capacity and power density of electrode materials. The Ni-foam (NF) substrate coupled with polypyrrole (PPy) conductive coating can serve as an internal/external bicontinuous conductive network. In this work, the distinctive PPy@FeNi2S4@NF and PPy@NiCo2S4@NF materials were prepared by a simple two-step hydrothermal synthesis with a subsequent in situ polymerization method. PPy@FeNi2S4@NF and PPy@NiCo2S4@NF could deliver ultrahigh specific capacitances of 3870.3 and 5771.4 F·g-1 at 1 A·g-1 and marvelous cycling capability performances of 81.39% and 93.02% after 5000 cycles. The asymmetric supercapacitors composed of the prepared materials provided a high-energy density of over 47.2 Wh·kg-1 at 699.9 W·kg-1 power density and 67.11 Wh·kg-1 at 800 W·kg-1 power density. Therefore, the self-assembled core-shell structure can effectively improve the electrochemical performance and will have an effective service in advanced energy-storage devices.

Exploring the Interfacial Reaction of Nano Al/CuO Energetic Films through Thermal Analysis and Ab Initio Molecular Dynamics Simulation.

The effect of the interface layer on energy release in nanoenergetic composite films is important and challenging for the utilization of energy. Nano Al/CuO composite films with different modulation periods were prepared by magnetron sputtering and tested by differential scanning calorimetry. With the increase in the modulation period of the nano Al/CuO energetic composite films, the interface layer contained in the energetic composite film decreased meaningfully, increasing the total heat release meaningfully. Ab initio molecular dynamics (AIMD) simulation were carried out to study the preparation process changes and related properties of the nano Al/CuO energetic composite films under different configurations at 400 K. The results showed that the diffusion of oxygen atoms first occurred at the upper and lower interfaces of CuO and Al, forming AlOx and CuxAlyOz. The two-modulation-period structure changed more obviously than the one-modulation-period structure, and the reaction was faster. The propagation rate and reaction duration of the front end of the diffusion reaction fronts at the upper and lower interfaces were different. The Helmholtz free energy loss of the nano Al/CuO composite films with a two-modulation-period configuration was large, and the number of interfacial layers had a great influence on the Helmholtz free energy, which was consistent with the results of the thermal analysis. Current molecular dynamics studies may provide new insights into the nature and characteristics of fast thermite reactions in atomic detail.

Recent Developments in Spectroscopic Techniques for the Detection of Explosives.

Trace detection of explosives has been an ongoing challenge for decades and has become one of several critical problems in defense science; public safety; and global counter-terrorism. As a result, there is a growing interest in employing a wide variety of approaches to detect trace explosive residues. Spectroscopy-based techniques play an irreplaceable role for the detection of energetic substances due to the advantages of rapid, automatic, and non-contact. The present work provides a comprehensive review of the advances made over the past few years in the fields of the applications of terahertz (THz) spectroscopy; laser-induced breakdown spectroscopy (LIBS), Raman spectroscopy; and ion mobility spectrometry (IMS) for trace explosives detection. Furthermore, the advantages and limitations of various spectroscopy-based detection techniques are summarized. Finally, the future development for the detection of explosives is discussed.