RESUMEN
Zn-BTC (H3BTC refers to 1, 3, 5-benzoic acid) MOF was used as a self-template and a zinc source to prepare ZnS/NiS2 with a layered heterogeneous structure as a promising electrode material using cation exchange and solid-phase vulcanization processes. The synergistic effect of the two metal sulfides enhances the application of ZnS/NiS2. And the high specific surface area and abundant active sites further promote the mass/charge transfer and redox reaction kinetics. In the three-electrode system, the specific capacitance was as high as 1547 F/g at a current density of 1 A/g, along with satisfactory rate capability (1214 F/g at 6 A/g) and cycling performance. Coupled with activated carbon (AC), the prepared hybrid device (ZnS/NiS2 as the positive electrode and AC as the negative electrode) (ZnS/NiS2/AC) can be operated under a potential window of 1.6 V and provides a high energy density of 26.3 Wh/kg at a power density of 794 W/kg. Notably, the assembled ZnS/NiS2//AC showed little capacity degradation after 5000 charge/discharge cycles.
RESUMEN
Real-time strain monitoring of large composite structures such as wind turbine blades requires scalable, easily processable and lightweight sensors. In this study, a new type of strain-sensing coating based on 2D MXene nanoparticles was developed. A Ti3C2Tz MXene was prepared from Ti3AlC2 MAX phase using hydrochloric acid and lithium fluoride etching. Epoxy and glass fibre-reinforced composites were spray-coated using an MXene water solution. The morphology of the MXenes and the roughness of the substrate were characterised using optical microscopy and scanning electron microscopy. MXene coatings were first investigated under various ambient conditions. The coating experienced no significant change in electrical resistance due to temperature variation but was responsive to the 301-365 nm UV spectrum. In addition, the coating adhesion properties, electrical resistance stability over time and sensitivity to roughness were also analysed in this study. The electromechanical response of the MXene coating was investigated under tensile loading and cyclic loading conditions. The gauge factor at a strain of 4% was 10.88. After 21,650 loading cycles, the MXene coating experienced a 16.25% increase in permanent resistance, but the response to loading was more stable. This work provides novel findings on electrical resistance sensitivity to roughness and electromechanical behaviour under cyclic loading, necessary for further development of MXene-based nanocoatings. The advantages of MXene coatings for large composite structures are processability, scalability, lightweight and adhesion properties.
RESUMEN
An approach for the synthesis of ZnAl-NO3 LDH conversion coatings on zinc in an aqueous acidic Al(NO3)3/NaNO3 solution is demonstrated for the first time. The growth mechanism has been investigated using time resolved structural, microstructural and analytical methods. A LDH growth model involving both electrochemical and chemical processes is suggested.
RESUMEN
Energy-transfer reactions are the key for living open systems, biological chemical networking, and the development of life-inspired nanoscale machineries. It is a challenge to find simple reliable synthetic chemical networks providing a localization of the time-dependent flux of matter. In this paper, we look to photocatalytic reaction on TiO2 from different angles, focusing on proton generation and introducing a reliable, minimal-reagent-consuming, stable inorganic light-promoted proton pump. Localized illumination was applied to a TiO2 surface in solution for reversible spatially controlled "inorganic photoproton" isometric cycling, the lateral separation of water-splitting reactions. The proton flux is pumped during the irradiation of the surface of TiO2 and dynamically maintained at the irradiated surface area in the absence of any membrane or predetermined material structure. Moreover, we spatially predetermine a transient acidic pH value on the TiO2 surface in the irradiated area with the feedback-driven generation of a base as deactivator. Importantly we describe how to effectively monitor the spatial localization of the process by the in situ scanning ion-selective electrode technique (SIET) measurements for pH and the scanning vibrating electrode technique (SVET) for local photoelectrochemical studies without additional pH-sensitive dye markers. This work shows the great potential for time- and space-resolved water-splitting reactions for following the investigation of pH-stimulated processes in open systems with their flexible localization on a surface.
