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

Abstract

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.

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 crystalline structure is an important part for LDH materials. It was reported that during the charging step, the surface of LDH materials is not the only part that participates, the entire crystalline structure is also involved via intercalation/de-intercalation of electrolyte ions; promoting the excellent energy storage capabilities of LDH materials [ 6 , 30 , 31 , 32 , 33 ]. Therefore, the LDH crystalline domain deserves attention.…”

“…Figure 2 d shows the FTIR spectra for the LDH-100-1h, LDH-100-1h30, LDH-100-2h, LDH-150-1h, and LDH-200-1h electrodes. Generally, the nature of the LDH interlamellar also determines the electrochemical performance [ 30 , 41 ]. Since it was difficult to understand the nature of the interlamellar for all the as-fabricated binder-free LDH electrodes using XRD, the FTIR measurements for all the binder-free LDH electrodes were carried out.…”

“…Figure 5 a displays the comparative CV curves for the LDH-100-1h, LDH-100-1h30, and LDH-100-2h electrodes at the scan rate of 10 mVs −1 in a voltage window of 0.6 V (vs. Ag/AgCl). As it can be seen, typical Faradaic peaks were noticeable for all the electrodes showing that their capacitances were the consequences of quasi-reversible faradaic redox reactions [ 30 , 49 , 50 ] due to the combined effects of nickel and cobalt within the LDH electrodes [ 51 ]. Moreover, it was depicted that the CV absolute area of the LDH-100-2h electrode was larger compared to those of the LDH-100-1h and LDH-100-1h30 electrodes indicating that its charge storage performance is excellent compared to its counterparts.…”

“…Thereafter, the specific capacitances for the LDH-100-1h, LDH-100-1h30, LDH-100-2h, LDH-150-1h, and LDH-200-1h electrodes were calculated from CV curves at the scan rate of 10 mVs −1 using Equation (6) [ 30 ], and the calculated values are presented in Table 2 . Meanwhile, Table 3 compared the specific capacitance of the LDH-200-1h electrodes with other reported NiCoAl-LDH electrodes.…”

“…The electrochemical impedance spectroscopy (EIS) measurements were also performed for the LDH-100-1h, LDH-100-1h30, LDH-100-2h, LDH-150-1h, and LDH-200-1h electrodes in a frequency ranging from 100 kHz to 100 mHz at open circuit potential. It is known that Rs shows the resistance of the electrolyte, while the charge transfer impedance on the interface electrode/electrolyte is represented by Rct [ 30 , 52 ]. Figure 9 a exposes the comparative Nyquist plots for the LDH-100-1h, LDH-100-1h30, LDH-100-2h electrodes.…”