Electrochemical Conversion of Salinity Gradient Energy via Molybdenum Disulfide Electrode

Abstract

The energy generated when sea water meets river water is called salinity gradient energy. At present, the main methods to extract salinity gradient energy are pressure-retarded osmosis, reverse electrodialysis and capacitive mixing technology. The selection of electrode materials has always been the focus of capacitive mixing technology. Here we report a device assembled based on capacitive mixing technology with molybdenum disulfide as anode and activated carbon as cathode. The energy density of the device is 6.12 J g-1, which shows that it has application prospects in the development of renewable energy.

Ionic Activity on a Manganese Phosphate Electrode for the Electrochemical Conversion of the Salinity Gradient Energy

“…Figure 6a,d is the GCD curves of the asymmetric supercapacitor in different electrolytes, and Figure 6b,e is the CV curves of the device in different solutions. According to the voltage windows of AC (−1 to 0 V) and Mn 3 (PO 4 ) 2 (−0.65 to 0.55 V), the voltage window of the capacitor in the CV and GCD tests is 0−1.55 V. The electrochemical capacities of the capacitor in these electrolytes are 30,31,36,27,34,38,90,93,105,80,85, and 95 F g −1 . It can be seen from the GCD diagram that the electrolyte has a certain influence on the capacity of the assembled asymmetric supercapacitor, and this influence is caused by the joint influence of AC and Mn 3 (PO 4 ) 2 .…”

“…Under the action of an electric field, the cations in the liquid at the solid–liquid interface spontaneously move away from the solid, while the anions spontaneously approach the solid. On the AC side is the electric double layer adsorption and desorption principle, and the potential of the diffusion layer can be obtained by the following formula: , φ d = 2 K B T e ⁡ sinh − 1 ⁡ ( σ 8 K B T N A ε c ) where K B is the Boltzmann constant, T is the temperature, e is the charge of a single electron, N A is the Avogadro constant, ε is the dielectric constant, and c is the concentration of the solution. With the solution concentrations of 0.02 and 1 mol L –1 Na 2 SO 4 solutions used in this experiment, the curves of the potential on the activated carbon side with the surface charge density are shown in Figure b.…”

“…According to the eqs 2 and 3, when the current density is 0.1 A g −1 , the energy densities of the assembled supercapacitor in the 12 electrolytes are 10.01, 10. 34 , respectively, indicating that the capacitor has excellent energy storage ability. It can be seen from the electrochemical data that in low concentration, the addition of Br − , K + , Mg 2+ , and Ca 2+ ions increase the electrochemical capacity of the AC-Mn 3 (PO 4 ) 2 capacitor, while the impact of the addition of the Mg 2+ ion is negative, and the capacity in 0.02M+ solution is larger than that in 0.02 mol L −1 Na 2 SO 4 .…”

“…Under the action of an electric field, the cations in the liquid at the solid−liquid interface spontaneously move away from the solid, while the anions spontaneously approach the solid. On the AC side is the electric double layer adsorption and desorption principle, and the potential of the diffusion layer can be obtained by the following formula: 33,34 = i k j j j j j y…”

Salinity Gradient Energy Harvesting via Na-Mn3(PO4)2-Based Electrochemical System

“…Due to the excellent electrochemical performance of manganese phosphate, in theory, it can be used to build a mixed capacitor to harvest water salinity gradient energy. ,− However, although manganese phosphate has high cycle stability and alkali resistance, its compact structure and poor conductivity will hinder the transfer of charges, which is unfavorable to the extraction of the water salinity gradient energy. In addition, the existing research cannot clearly show the influence of electrolyte ion type on the imbedding/deinterlacing of layered structure of manganese phosphate during the charge–discharge process. ,, So, in this paper, manganese phosphate hydrate is used as the main material to build a mixed capacitor with activated carbon, test its performance, and harvest water salinity gradient energy. At the same time, a sample of Na + -modified manganese phosphate was prepared by preinserting heteroatoms with lower electronegativity.…”