Increasing Electrolyte Concentration Research Articles

Unlocking the role of electrolyte concentration for Na-O2 batteries

Na-O2 batteries have attracted great interest in recent years mainly due to their high energy density, in theory having prospects to outperform the commercialized lithium-ion batteries. In the quest for optimization, a recently explored approach is to use highly concentrated electrolytes (HCEs). The knowledge of molecular level of solvation as function of electrolyte concentration and its impact on Na-O2 battery performance is, however, still very limited. In this work, experimental and computational methods are used to characterize the cation solvation and when the emergence of anions into the cation first solvation shell occurs, which affects the de-solvation process and formation of discharge products. Furthermore, the solid electrolyte interphase (SEI) formed using HCEs demonstrates presence of anion fragments, with poorer protection of the Na metal anode. Moreover, the use of HCEs is also linked to lowered capacity, possibly due to a decrease in the size of the cubic-shaped discharge products as the electrolyte concentration increases, causing clogging of the pores of the air cathode. Thus, increasing the electrolyte salt concentration seems to have a detrimental effect on the cyclability of Na-O2 batteries. Instead, electrolytes with a lower than conventional salt concentration show the best performance, which highlights the importance of carefully tuning the cation solvation alongside overall physico-chemical properties to enhance battery performance.

Effects of NaOH Concentration and Plate Surface Texture on the Performance of the HHO Generator

The need for clean energy as an alternative is inevitable. HHO gas has received much attention lately. In addition to electrolyte concentration, the breakthrough with a diverse electrode surface texture approach has not been extensively performed. Therefore, this study aims to determine the effects of NaOH concentration and plate surface texture on the performance of the HHO generator. In general, the increase in electrolyte concentration combined with surface texture caused an increase in output current, HHO gas production, and output temperature. As for the applied voltage variation with various surface textures, the increase in output current, HHO gas production, and output temperature also took place, similar to the case of increasing NaOH concentration. Either an increase in electrolyte concentration or an increase in applied voltage triggers faster ion movement, leading to an increase in conductivity, thus effectively assisting the electrolysis of water. Regarding the output current and HHO gas production, the textured surface had a much higher value than the plain surface in terms of increasing NaOH concentration or applied voltage variations. However, according to the R2 results, the linear surface has a stronger relationship with the output current and HHO gas production than the cross surface. In the case of the output temperature, the linear surface was slightly lower than the cross surface. It is possibly due to impurities in the electrolyte solution that contaminate the electrode surface, resulting in a lower output temperature on the linear surface.

Exploring the influence of KOH electrolyte concentration on the electrochemical properties of Co3O4-GO nanocomposite

In this study, we investigate the electrochemical performance of Co3O4-GO nanocomposite, synthesized via a hydrothermal method, as a function of electrolyte concentration. XRD, Raman, SEM, TEM, XPS, and BET techniques have been employed to examine the structural, microstructural, chemical states, and specific surface area characteristics of the composite material. According to SEM micrographs, the aggregated particles have a sheet-like morphology, and these sheets have been assembled into clusters. Using N2-adsorption/desorption isotherms, the pore volume, diameter, and specific surface area of composite were determined to be 0.24 cm3/g, 15 nm, and 63 m2/g, respectively. Based on cyclic voltammograms (CVs) recorded at different scan rates and electrolyte concentrations, the working electrode demonstrated pseudocapacitance behavior. The specific capacitance (Cs) of the fabricated electrode was estimated from GCD curves recorded at different current densities and electrolyte concentrations. For 1 M KOH solution, Cs of the composite electrode is found to be 258 F/g at 1 A/g, and this value drops to 222 F/g at 5 A/g. Furthermore the composite electrode's Cs decreases with increasing electrolyte concentration at a specific current density. The study indicates that 1 M of KOH electrolyte is the optimal electrolyte concentration for optimal energy storage.

A study on the solubility of some amino acids in (H2O + EtOH) and (H2O + EtOH + NaI) systems by gravimetric method at T = 298.15 K: Experimental measurements and COSMO-RS calculations

In this study, the solubility of three amino acids including glycine, L-alanine, and L-valine was measured using the gravimetric method in aqueous mixtures with 0–100 % (w/w) ethanol in different salt concentrations of sodium iodide (from 0 to 2 mol kg−1) at 298.15 K and 89.1 kPa. The Setschenow equation was used to analyze the effect of the electrolyte on solubility. In addition, the multi-parameter Kamlet-Taft (KAT) equation was applied to provide detailed information on the solute–solvent and solvent–solvent interactions. Moreover, the molecular interactions in the solvent mixture were qualitatively investigated using the COSMO-RS method. The results showed that the solubility of each amino acid increases with increasing electrolyte concentration and decreases with increasing ethanol content in the solvent mixture. The Setschenow equation and experimental solubility data showed NaI's salting-in effect in the solubility process for all amino acids. It was found that the polarity-polarizability parameter of the solvent system has the most significant effect on the solubility of the amino acids. According to the COSMO-RS calculations, glycine and solvent system favor hydrogen bonding interactions while L-alanine and L-valine tend to interact with solvent more through hydrophobic interactions.

Transformations in crystals of DNA-functionalized nanoparticles by electrolytes.

Colloidal crystals have applications in water treatments, including water purification and desalination technologies. It is, therefore, important to understand the interactions between colloids as a function of electrolyte concentration. We study the assembly of DNA-grafted gold nanoparticles immersed in concentrated electrolyte solutions. Increasing the concentration of divalent Ca2+ ions leads to the condensation of nanoparticles into face-centered-cubic (FCC) crystals at low electrolyte concentrations. As the electrolyte concentration increases, the system undergoes a phase change to body-centered-cubic (BCC) crystals. This phase change occurs as the interparticle distance decreases. Molecular dynamics analysis suggests that the interparticle interactions change from strongly repulsive to short-range attractive as the divalent-electrolyte concentration increases. A thermodynamic analysis suggests that increasing the salt concentration leads to significant dehydration of the nanoparticle environment. We conjecture that the intercolloid attractive interactions and dehydrated states favour the BCC structure. Our results gain insight into salting out of colloids such as proteins as the concentration of salt increases in the solution.

Effect of Electrolyte Anions on the Activity of Iridium Oxide Catalysts for Water Electrolysis

Developing environmentally friendly and renewable energy sources is essential due to the environmental and energy security issues caused by traditional combustion of fossil fuel-based energy sources. Therefore, as a clean and sustainable energy carrier, hydrogen has attracted great attention in recent years. In this regard, water electrolysis utilizing renewable energy sources to produce hydrogen is considered one of the most promising technologies. It is believed elucidation of the reaction mechanism of highly active iridium oxides is promising for the further development of cost-efficient PEM water electrolysis catalysts. The properties of the MEA could be affected by many parameters such as the catalysts, operating temperature, and pressure1,2. Another important factor is the cation impurities that can be found in the circulating water, which could severely degrade the MEA performance during the operation of a PEM water electrolyze. However, there are less reports on anion impurities such as SO4 2- and PO4 3-. Therefore, in this study, the relationship between electrolyte anions and OER activity was investigated for IrOx catalysts with different crystal structure. By using operando X-ray absorption spectroscopy (XAS), we investigated the electronic state of Ir and O under operation potential.IrOx with different degree of crystallinity (SA3.5 and SA58) were provided by Tanaka Kikinzoku Kogyo K.K., Chemical & Refining Company and named after their BET surface areas. These two samples were then tested for electrochemical properties in different concentrations of phosphoric acid and perchloric acid, respectively. The electrochemical measurements were performed using a standard three-electrode cell connected to an MPG-205-NUC system (Bio-Logic). The cyclic voltammograms (CV) were scanned from 0.1 V to 1.2 V vs. RHE at 50 mV s-1. The electrochemical activities of the catalysts were subsequently investigated using linear sweep voltammetry (LSV) in the range of 1.1 to 1.7 V vs RHE at 10 mV s−1. operando XAS were collected using a home-made flow-type cell, where Pt wire and RHE worked as counter and reference electrodes, respectively. The catalyst ink was coated onto an Nafion membrane to prepare both the X-ray window and working electrode. The electrolyte was circulated at the flow rate of 100 mL min-1.The catalytic performance of IrOx was investigated at different types and content of electrolyte under H3PO4 and HClO4. Figure 1 shows the CVs of SA3.5 and SA58 under different types and content of electrolyte. In the presence of phosphate anions, SA3.5 showed a tendency to decrease Ir redox between 0.6 and 1.1 V with increasing electrolyte concentration. On the other hand, there were no obvious changes in SA58. It was found that IrOx catalysts have an great effect of specific adsorption of anions and low symmetry of monoclinic phase catalysts (SA 3.5) are more susceptible to anion poisoning. Figure 2 shows the result of examining the poisoning mechanism using soft X-ray XAS. O K-edge results present the formation of µ2-O (O-O) bond at around 528.7 eV, which was previously observed by Nong, H. N. et. al. through operando O-K edge measurements during OER process3. The peak intensity at 528.7 eV of the amorphous samples was in the same order as the OER activities. According to potential dependence change of the pre-edge peak, under the presence of phosphate anions, the hole formation to Ir-O hybrid orbitals was suppressed in SA3.5. This result indicates that the anion adsorbs to the active site, poisoning the catalyst surface and inhibiting the reaction. Acknowledgements This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References Zhang, Y.; Zhu, X.; Zhang, G.; Shi, P.; Wang, A.-L.; et al. J. Mater. Chem. A: 2021, 9, 5890-5914.Chen, Z.; Duan, X.; Wei, W.; Wang, S.; Ni, B.-J.; et al. Nano Energy: 2020, 78, 105270.Nong, H. N.; Falling, L. J.; Bergmann, A.; et al. Nature 2020, 587 (7834), 408-413. Figure 1

Interfacial Chemistry in Aqueous Lithium-Ion Batteries with Dilute Aqueous Electrolytes: A Case Study with V2O5

Aqueous lithium ion batteries (ALIBs) are promising candidates for large-scale energy storage systems, benefiting from the intrinsic safe and environmentally friendly properties of aqueous electrolytes. However, its practical application is impeded due to the narrow electrochemical stability windows (ESWs) of aqueous electrolytes. Despite that increasing electrolyte concentration can achieve a wide ESW with the protection of SEI layer, it brings numerous disadvantages induced by excessive salt as well. Therefore, understanding the SEI formation mechanism and further widening the ESWs of dilute aqueous electrolytes are critical for the breakthrough of next-generation ALIBs.Herein, the interphase chemistry of V2O5 electrode with dilute aqueous electrolyte was systematic investigated by conducting various Operando characterizations with LMO||V2O5 cell system. Dynamic SEI, which consists of Li2CO3, LiF and V2O4, was formed during charge and disappeared during the following discharge, which is strongly affected by electrolyte pH fluctuation. Moreover, its evolution process is reversible during cycling. There are several impacts affect the pH fluctuation during cycling. First, V2O5 dissolution, which turns electrolyte into acidic before cycling, and is aggravated by electrolyte concentration decrease. Second, proton/hydronium ion insertion, which takes place on electrode surface in dilute electrolyte, while it is suppressed by concentration increase due to reduced proton concentration. Third, the redox reaction of dissolved V2O5, which is controlled by both potential and electrolyte pH change according to the V-H2O poubaix diagram. Along with the anode potential decrease and the alkalinisation of electrolyte, V2O4 is formed on anode surface by the reduction of HV10O28 5- and V4O12 4- and this reduction process further produces hydroxide ion into electrolyte. Last, the carbon oxidation, which takes place on cathode side during charge and on anode side during the final discharge. Therefore, the acidification of electrolyte during cycling is detrimental to SEI stability in aqueous electrolytes. This systematic research work provides new perspectives to the understanding of the interphase chemistry evolution in aqueous Li-ion batteries using dilute electrolytes, which guides the building of effective SEI layer in aqueous Li-ion batteries and beyond. Figure 1

Adsorption Behaviors of Lanthanum (III) and Yttrium (III) Ions on Gibbsite

The enrichment process of rare earth elements in ion-adsorbed rare earth ores and bauxite is potentially related to the adsorption of rare earth elements by gibbsite. In this paper, lanthanum and yttrium were selected as surrogates of light rare earth elements and heavy rare earth elements, respectively. The effects of adsorption time, solution pH, and background electrolyte concentration on the adsorption of rare earth ions by gibbsite were investigated through batch adsorption experiments. The results showed that the adsorption of rare earth ions by gibbsite can approach equilibrium in 72 h. There is mainly electrostatic repulsion between gibbsite and rare earth ions at pH 4–7, and the adsorption efficiency increases with the increase in solution pH value and background electrolyte concentration. The adsorption process of rare earth ions by gibbsite is more consistent with the pseudo-second-order kinetic and Langmuir single-layer adsorption models. Moreover, based on the structural correlation between clay minerals and gibbsite, the causes for the differences in the adsorption behaviors of rare earth elements on the minerals are discussed. The results of this study help to understand the role of aluminum hydroxide in the migration and fate of rare earth elements in epigenetic environments.

Effects of electrolyte type and concentration on the anodic oxidation of 4H-SiC (0001) in slurryless electrochemical mechanical polishing

Slurryless electrochemical mechanical polishing (ECMP) is a promising polishing method for SiC wafers. To achieve a high polishing efficiency, low surface roughness, low cost, and low environmental load, the effects of the electrolyte type and concentration on the anodic oxidation and ECMP of the 4H-SiC (0001) surface were investigated. It is confirmed that the anodic oxidation rate is mainly affected by the conductivity but not the type of electrolyte, and the electric conductivity affects the oxidation current that determines the anodic oxidation rate and performance. The anodic oxidation rate of the SiC surface was restricted by the conductivity at low electrolyte concentrations, and the anodic oxidation rate increased with increasing electrolyte concentration in this stage. The anodic oxidation rate decreased with increasing electrolyte concentration after the conductivity exceeded ∼0.1 S/m, owing to the increasing resistance of the generated oxide layer. Overall, the anodic oxidation uniformity of the SiC surface increased with increasing electrolyte concentration owing to the increasing anodic oxidation current density. The changes in material removal rate of ECMP with increasing electrolyte concentration were consistent with those of the anodic oxidation rate, while the surface roughness obtained by ECMP always decreased with increasing electrolyte concentration. This study provides a new way to improve the performance of slurryless ECMP.

Efficient (Bio)emulsification/Degradation of Crude Oil Using Cellulose Nanocrystals

This study has investigated the influence of cellulose nanocrystals (CNCs) with partially acetylated surfaces on the formation, stability, rheology and biodegradability of the Pickering emulsion in a crude oil/water (co/w) system. In all investigated systems, it was observed that the CNC concentrations of 7 mg/mL led to the emulsions showing stability over time. It was also noticed that the increase in concentration of background electrolyte (NaCl) leds to the droplets of emulsions becoming smaller. It was demonstrated that the rheology of the o/w emulsions of the oil products and crude oil stabilized by CNCs depends, to a large extent, on the colloid chemical properties of nanocellulose particles. Calculations and experimental methods were used to study the changes in the acid–base properties of CNCs on the surface of emulsion droplets, depending on a type of hydrophobic components (crude oil and liquid paraffin). The formation of Pickering emulsions leads to the oxidation of oil by Rhodococcus egvi in aerobic conditions becoming more effective, provided that the environment includes mineral salts of nitrogen, potassium and phosphorus. The results obtained present a scientific basis for the development of technologies for the disposal of oil spills on water surfaces.

Electrochemical Characterization of Salt-in-Water and Water-in-Salt Zinc Sulfate and Zinc Acetate Electrolytes

The electrochemical properties of Zn(OAc)2 or ZnSO4 with water at different concentrations are investigated. The electrochemical stability window follows Pt < Au < glassy carbon electrodes, and expands with increasing concentration of electrolytes. The change in salt concentration does not significantly change the double layer capacitance, and the potential of zero charge of Pt, Au and glassy carbon electrodes are estimated to be 0.25–0.35 VSCE, 0.05 VSCE, and –0.20 VSCE, respectively. With hydroquinone as the redox probe, the redox electrochemistry, ion transport and electron transport kinetics in these electrolytes are studied. The apparent redox potential of hydroquinone increases with the electrolyte concentration, and the diffusion coefficients of hydroquinone in Zn(OAc)2 and ZnSO4 electrolytes decrease with the increase of electrolyte concentration. The electron transfer rate constants (k) between the electrode and hydroquinone in Zn(OAc)2 and ZnSO4 electrolytes range in 1.28–1.46 cm s−1 and 0.29–0.81 cm s−1, respectively. The lower k in ZnSO4 electrolytes is related to the lower solvent reorganization energy, the interaction of electroactive ions with water, and the interaction of electrolyte cations.

Kinetic Transport Coefficients Through a Bilayer Ion Exchange Membrane during Electrodiffusion

Analytical expressions for the specific coefficients of electrical conductivity and electrodiffusion through a bilayer ion exchange membrane during the electrodiffusion process are obtained within the framework of thermodynamics of irreversible processes and a homogeneous model of a fine-porous membrane. The influence of physicochemical characteristics of the modifying layer and electrolyte concentration on the values of the obtained coefficients at fixed physicochemical characteristics of the substrate has been investigated by the method of mathematical modelling. It is shown that electrical conductivity and electrodiffusion of the modified membrane at coincidence of signs of volume charges of the membrane layers increase with an increase of density of volume charge of the modifying layer and decrease at their difference or an increase of thickness of the modifying layer. With increasing electrolyte concentration, the abovementioned characteristics of the modified membrane increase regardless of the sign of the charges of the membrane layers. The obtained analytical expressions can be used in modelling electromembrane processes and predicting the parameters of new surface modified ion exchange membranes.

Diffusion of Fe3+ Ions in Agar Gel Medium Containing Zinc Sulfate: Obstruction effect and Activation Energy

The paper presents a study on the diffusion behaviour of ferric ions within an agar gel medium containing zinc sulfate electrolyte. Investigations for various aspects, including the obstruction effect introduced by the agar gel, the validation of Wang's diffusion model, and the suitability of applying transition state theory to the diffusion of Fe3+ ions in an agar gel medium with zinc sulfate were made. This investigation involved optimising the gel concentration, electrolyte concentration, and system temperature. The diffusion coefficients are determined by the zone diffusion technique. The results reveal that the activation energy (E) decreases as the electrolyte concentration increases, aligning with Wang's model. This decrease is attributed to the disruption of the water structure induced by ions and agar molecules. Additionally, for a fixed electrolyte concentration, the activation energy decreases with the cubic root of the weight percent of agar (W1/3), while the diffusion coefficient (Do) decreases with the square of the reciprocal of the weight percent of agar (W-2/3). This behaviour is consistent with the principles of the transition state theory of diffusion.

Promoting Homogeneous Zinc-Ion Transfer Through Preferential Ion Coordination Effect in Gel Electrolyte for Stable Zinc Metal Batteries.

Aqueous zinc metal batteries (AZMBs) are emerging energy storage systems that are poised to replace conventional lithium-ion batteries owing to their intrinsic safety, facile manufacturing process, economic benefits, and superior ionic conductivity. However, the issues of inferior anode reversibility and dendritic plating during operation remain challenging for the practical use of AZMBs. Herein, a gel electrolyte based on zwitterionic poly(sulfobetaine methacrylate) (poly(SBMA)) dissolved with different concentrations of ZnSO4 is proposed. Two-dimensional correlation spectroscopy based on Raman analysis reveals an enhanced interaction priority between the polar groups in SBMA and the dissolved ions as electrolyte concentration increases, which establishes a robust interaction and renders homogeneous ion distribution. Attributable to the modified coordination, zwitterionic gel polymer electrolyte with 5molkg-1 of ZnSO4 (ZGPE-5) facilitates stable zinc deposition and improves anode reversibility. By taking advantage of preferential coordination, a symmetrical cell evaluation employing ZGPE-5 demonstrates a cycle life over 3600 h, where ZGPE-5 also exerts a beneficial effect on the full cell cycling when assembled with Zn0.25 V2 O5 cathode. This study elucidates changes in the internal ion behavior that are dependent on electrolyte concentrations and pave the way for durable AZMBs.

Intensified treatment of kitchen wastewater in a filter- press type electrochemical reactor

Commercial kitchen wastewater (KW), characterized by a high load of bio-refractory organics, can be effectively treated by electrochemical methods for non-potable applications. This work explores the electrochemical degradation of KW in a batch recirculation type flow reactor consisting of mixed metal oxides coated titanium mesh anode and stainless steel cathode. The effect of operating factors such as current density, supporting electrolyte concentration, initial pH, and recirculation flow rate on chemical oxygen demand (COD) reduction was examined by following one-factor-at-a-time method. The %COD reduction increased with an increase in electrolyte concentration and current density. The optimum current density and electrolyte concentration were found to be 2 A/dm2 and 2 g/L, respectively. The treatment was intensified by incorporating mechanical stirring and ultrasound irradiation in the reservoir. The results showed about 99 % COD reduction, and the kinetic model proposed predicted the experimental data satisfactorily.

A new surface structural approach for modeling the charging behavior of kaolinite

The concentration of ions in equilibrium with soils and sediments is a function of various interconnected chemical reactions. The charging behavior of minerals provides a set of fundamental information required to model these interactions. Accordingly, in this study, the charging behavior of kaolinite was measured at three concentrations (0.004, 0.04 and 0.40 M) of three electrolytes (LiNO3, NaNO3 and KNO3) using potentiometric titration. The experimental data were described using the CD-MUSIC-G&T model in which ≡AlOH0.5−, ≡SiO− and ≡X− were defined as reactive functional groups on aluminol edge, silanol edge and basal planes, respectively. The charging behavior was a function of the type and concentration of the background electrolytes, but changes in the concentration more than changes in the type of electrolytes affected the surface charge. The thermodynamic equilibrium constants (logK) of the reactions of H+, Li+, Na+, K+ and NO3− with aluminol group were obtained as 9.50, 1.62, 1.37, 1.29 and 10.28 and with silanol group as 4.94, 1.58, 1.79, 2.03 and < −10, respectively. The logK of 4.94 shows that the interaction of H+ ion with the kaolinite ≡SiO− is much stronger than its interaction with the same group on the quartz. The capacitance of both inner and outer Stern layers was measured to be 1.94 F/m2, showing the strong interaction of electrolyte ions with the edge surface. In addition, the equilibrium constants of the reactions of Li+, Na+ and K+ with ≡X− group were obtained as −0.40, −0.02 and 0.32, respectively, which have the same order as reacted with the silanol group. At pH below pHPZC (i.e., <6.3 ± 0.2), increasing ionic strength reduced the surface charge of kaolinite; because increasing electrolyte concentration increased the negative charge on the silanol edge more than increasing the positive charge on the aluminol edge. In addition, it seems that the negative potential due to the isomorphic substitution in the polyhedrons near the edge of kaolinite poses an inward attractive force on the central cations of the edge polyhedrons, which in turn reduces the bonding capacity of ≡Al−OH0.5− and/or ≡Si−O−. Thereby, the adsorption energy of proton and cations on the edge surface may increase due to isomorphic substitution in adjacent polyhedrons.

Anti-Alzheimer Drug Delivery via Pickering Emulsions Stabilized by Plate-like Cellulose Nanocrystals.

In this work, we studied for the first time the formation of olive oil emulsions in water stabilized by plate-like nanocrystals with the supramolecular structure of cellulose II (pCNC). Effects of storage, pCNC concentration, and NaCl on the stability and properties of Pickering emulsions, including the creaming index, droplet size, zeta potential, acid-base surface properties, and rheology, were studied. A significant influence of the shape of nanoparticles (compared to the classical rod-like shape) on the stability parameters and rheological characteristics of emulsions is shown. Plate-like cellulose nanocrystals at a concentration of 16 g/L are able to form delamination-resistant emulsions without added electrolytes. The viscosity of pCNC-stabilized emulsions tends to decrease with increasing electrolyte concentration in the system, which is not characteristic of rod-like CNC-stabilized emulsions. This effect in pCNC-stabilized emulsions assumedly can be associated both with weak mechanical engagement between drops due to the shape of stabilizer particles and with an insignificant participation of background electrolyte cations in the formation of interdroplet interactions. Therefore, the resulting aggregates are unstable and easily destroyed, even under weak mechanical stress. As a consequence, the acid-base properties of the pCNC surface are practically independent of the emulsion preparation method (with or without electrolyte) as well as the concentration of the background electrolyte. The reduced viscosity of pCNC-stabilized emulsions in the presence of an electrolyte, coupled with the absence of acute toxicity, allows us to recommend them as a convenient oral delivery system for fat-soluble, biologically active substances. Our emulsions carrying donepezil (an anti-Alzheimer drug) showed better performance than a solution of donepezil hydrochloride in preventing memory impairment tested on laboratory mice.

High-Power-Density Thermoelectrochemical Cell Based on Ni/NiO Nanostructured Microsphere Electrodes with Alkaline Electrolyte.

Effective low-grade waste heat harvesting and its conversion into electric energy by the means of thermoelectrochemical cells (TECs) are a strong theme in the field of renewable energy investigation. Despite considerable scientific research, TECs have not yet been practically applied due to the high cost of electrode materials and low effectiveness levels. A large hypothetical Seebeck coefficient allow the harvest of the low-grade waste heat and, particularly, to use TECs for collecting human body heat. This paper demonstrates the investigation of estimated hypothetical Seebeck coefficient dependency on KOH electrolyte concentration for TECs with hollow nanostructured Ni/NiO microsphere electrodes. It proposes a thermoelectrochemical cell with power density of 1.72 W·m-2 and describes the chemistry of electrodes and near-electrode space. Also, the paper demonstrates a decrease in charge transfer resistance from 3.5 to 0.52 Ω and a decrease in capacitive behavior with increasing electrolyte concentration due to diffusion effects.

Effect of Electrolyte Concentration on Characteristics of Activated Carbon of Cocoa Peel

Cocoa peel activated carbon has been successfully synthesized with 0.3 M KOH activator and NaCl electrolyte as the base material for supercapacitor electrodes. Variations in the concentration of NaCl electrolyte used were 1 M, 2 M, and 3 M to determine their effect on the capacitance, conductivity, and pore area values produced. The activated carbon produced was characterized by Scanning Electronic Microscope (SEM) to see surface morphology, X-Ray Diffraction (XRD) to determine carbon crystals, Cyclic Voltammetry (CV) and LCR-Meter to determine capacitance and conductivity values, and the Brunauer Emmett Teller method. (BET) to measure its surface area. The results of the Indonesian National Standard (SNI) test results obtained water content (8.6%), ash content (8.7%), volatile matter (26.2%), carbon content (65.1%), and iodine absorption (800 mg/g). The pore surface area can be increased by activation up to 24,742 m2/g. XRD analysis shows that the atomic structure is amorphous. Surface morphology proves that the increase in NaCl electrolyte concentration affects the pore structure. The higher the electrolyte concentration, the more even and finer the pore structure will be. The highest specific capacitance value was obtained at 3 M NaCl, which was 1.68375 F/g and the lowest was at 0.10771 F/g NaCl 1 M. The conductivity obtained is 1.83 S/m at 3 M NaCl at frequency of 1000 Hz and the lowest is 0.18 S/m at 1 M NaCl at 100 Hz. This proves that the electrolyte concentration can affect and increase the value of the capacitance and conductivity of the supercapacitor electrode.

Modulating the chiral nematic structure of cellulose nanocrystal suspensions with electrolytes

HypothesisThe iridescent optical properties of films made of cellulose nanocrystals (CNC) are controlled by the pitch and range of the chiral nematic structures. These are further tuned with the addition of electrolyte. ExperimentsElectrolyte type, valency and concentration were varied. The bulk CNC suspension properties were investigated by combining rheology, polarised optical photography and microscopy, while the spacing between crystals was determined using SAXS. FindingsThe addition of electrolyte to a CNC suspension containing chiral nematic structures first causes the nematic pitch to increase indicating the suspension has a weaker structure. Further increases in electrolyte concentration cause aggregation and complete breakdown of the chiral nematic structures. The univalent species cause larger changes to the chiral nematic structure with the onset and magnitude of structure breakdown occurring at lower ionic strengths compared with the divalent species. Cation size influences the chiral nematic structure with the order of influence being K+ > Na+ ≈ Ca2+ > Mg2+, which corresponds from the largest to smallest cation. This work demonstrates that both ion valency, concentration and species play a significant role in controlling the chiral nematic structures of CNC suspensions and will be a vital step in the development of CNC liquid crystals, optical materials and sensors.