Enhanced cycling stability performance for supercapacitor application of NiCoAl-LDH nanofoam on modified graphite substrate

Optimizing gas pressure for enhanced tribological properties of DLC-coated graphite

In this study, for the first time, the optimization of applied pressure for achieving the one of the best tribological properties of diamond-like carbon (DLC) coating on graphite surface using plasma-enhanced chemical vapor deposition (PECVD) method was investigated. Raman spectroscopy and microscopy methods were used to characterize the applied coating. Additionally, the mechanical properties of the coating were investigated through nanoindentation testing. The wear resistance of coating has been tested as functional test. The results indicated that with increasing gas pressure, the sp3 hybridization percentage decreases, while the ID/IG ratio increases. The average roughness values for the uncoated sample and the coated samples at working pressures of 25, 30, and 35 mTorr were obtained as 1.6, 5.1, 3, and 2.4 nm, respectively. The results of hardness and wear tests showed that these properties were optimized by reducing the applied gas pressure. The highest hardness was 11.59 GPa, and the best sample in terms of the mechanical properties of the coating was the sample applied at a gas pressure of 25 mTorr. Results show that the optimal sample in tribological performance is the one applied at a working pressure of 25 mTorr. Because this sample demonstrates the lowest coefficient of friction, and wear depth.

Advantage of Dimethyl Sulfoxide in the Fabrication of Binder-Free Layered Double Hydroxides Electrodes: Impacts of Physical Parameters on the Crystalline Domain and Electrochemical Performance

The electrode fabrication stage is a crucial step in the design of supercapacitors. The latter involves the binder generally for adhesive purposes. The binder is electrochemically dormant and has weak interactions, leading to isolating the active material and conductive additive and then compromising the electrochemical performance. Designing binder-free electrodes is a practical way to improve the electrochemical performance of supercapacitors. However, most of the methods developed for the fabrication of binder-free LDH electrodes do not accommodate LDH materials prepared via the co-precipitation or ions exchange routes. Herein, we developed a novel method to fabricate binder-free LDH electrodes which accommodates LDH materials from other synthesis routes. The induced impacts of various physical parameters such as the temperature and time applied during the fabrication process on the crystalline domain and electrochemical performances of all the binder-free LDH electrodes were studied. The electrochemical analysis showed that the electrode prepared at 200 °C-1 h exhibited the best electrochemical performance compared to its counterparts. A specific capacitance of 3050.95 Fg^-1 at 10 mVs^-1 was achieved by it, while its Rct value was 0.68 Ω. Moreover, it retained 97% of capacitance after 5000 cycles at 120 mVs^-1. The XRD and FTIR studies demonstrated that its excellent electrochemical performance was due to its crystalline domain which had held an important amount of water than other electrodes. The as-developed method proved to be reliable and advantageous due to its simplicity and cost-effectiveness.

Investigating the Impact of the Washing Steps of Layered Double Hydroxides (LDH) on the Electrochemical Performance

The washing of layered double hydroxides (LDH) material is mostly purposed to discard the unreacted products after the reaction has been completed. However, this study demonstrated that the washing stage can also be targeted to optimise the electrochemical performance of LDH by using an appropriate solvent. Solvents, namely, ethanol, acetone, and an ethanol-acetone solution (2:1) were used for the washing of LDH and the impacts thereof on the structural, physical, chemical, morphological, and electrochemical properties were investigated. Using Williamson-Hall analysis, we observed modifications on the crystalline domain. The specific surface area and pore parameters for all the samples were also differently affected. The Fourier transform infrared (FTIR) measurements displayed evident changes in the basic sites. The electrochemical performances of samples were analysed. The sample washed with the ethanol-acetone solution exhibited a specific capacitance of 1807.26 Fg-1 at 10 mVs-1, which is higher than that of other samples as well as low internal resistance compared to its counterpart. This demonstrates that the use of an appropriate solvent during the washing stage of LDH affects the electrochemical properties.