Increasing KCl Concentration Research Articles

Biomimetic kartogenin containing κ-carrageenan hydrogel for nucleus pulposus regeneration

Intervertebral disc degeneration is a clinical disease that reduces the quality of patient's life. The degeneration usually initiates in the nucleus pulposus (NP), hence the use of hydrogels represents a promising therapeutic approach. However, the viscoelastic nature of hydrogel and its ability to provide biomimetic architecture and biochemical cues influence the regeneration capability. This study focused on tuning the physical nature of a glycosaminoglycan hydrogel (κ-carrageenan) as well as the release kinetics of a chondrogenic factor (kartogenin - KGN) through physical cross-linking. For this, κ-carrageenan was cross linked with 2.5 % and 5 % potassium chloride (KCl) for 15 and 30 min and loaded with KGN molecule at 50 μM and 100 μM. The tight network structure with low water retention and degradation property was seen in hydrogel cross-linked with increased KCl concentration and time. However, optimal degradation along with NP mimicking viscoelastic nature was exhibited by 5 wt% KCl treated hydrogel (H3 hydrogel). All hydrogel groups exhibited burst KGN release at 24 h followed by a sustained release for 5 days. However, hydrogel cross-linked with 5 wt% KCl enhanced chondrogenic differentiation, mainly at lower KGN dose. In summary, this study shows the potential application of biomimetic KGN laden carrageenan hydrogel in NP regeneration.

Preparation of α-calcium sulfate hemihydrate with high mechanical strength from natural fibrous gypsum in KCl-mediated glycerol-water solution

Natural fibrous gypsum is a kind of high-quality gypsum resources, whose high-value added utilization pathway is to be transformed to α-calcium sulfate hemihydrate (α-HH), a cementitious material that can react with water to form pastes with mechanical strength. In this work, α-HH was prepared from natural fibrous gypsum in KCl mediated glycerol-water solution under mild condition. KCl played a simultaneous function on regulating the phase-transition kinetics, morphology and comprehensive strength of α-HH. Addition of low concentration of KCl prominently retarded the nucleation and growth rate of α-HH and decreased its aspect ratio due to the formation of syngenite on the side faces. While further increase of KCl concentration accelerated the nucleation and growth rate and decreased the crystal sizes. In the presence of 0.04 M KCl, the prepared α-HH presented a hexagonal prism shape with a length / width of 257.69–579.71 μm / 13.13–36.61 μm, and its dry comprehensive strength had reached 38.1 MPa that was comparable to those prepared in commercial, chloride and nitrate system. Altogether, the foreign ion-free glycerol-water solution contributed to transforming natural fibrous gypsum to α-HH with high purity and high mechanical strength.

LOW FREQUENCY DIELECTRIC PROPERTIES OF AGRICULTURE SOIL CONTAMINATED BY POTASH CHEMICAL FERTILIZERS

Present paper investigates the impact of potash (KCl) contamination on the low-frequency (100 Hz - 1 MHz) dielectric properties of agricultural soil from the western Dhule district, India. Soil samples were spiked with varied KCl concentrations (0, 5, 10, and 20 mg) and analyzed using an LCR meter to measure dielectric constant, impedance, dielectric loss, and admittance. Results demonstrate a proportional increase in dielectric constant with increasing KCl concentration, indicating enhanced polarization within the soil matrix. Conversely, impedance and admittance displayed opposite trends, with impedance decreasing and admittance increasing as KCl concentration rose. Dielectric loss also exhibited a positive correlation with KCl content. This comprehensive investigation sheds light on the dynamic interplay between soil composition and dielectric properties under varying potash concentrations, contributing valuable insights to agricultural and environmental sciences.

Fractionation and transport of compost‐derived dissolved organic matter fractions in saturated red soil and black soil columns

AbstractThe fractionation and transport of compost‐derived dissolved organic matter (DOMC) could affect the transport and fate of nutrients and DOM‐associated pollutants in the soil environment. In this study, the humic acid fraction of DOMC (HAC) and fulvic acid fraction of DOMC (FAC) were selected to investigate the fractionation and transport of DOMC in repacked soil columns of a red soil and a black soil under different KCl concentrations. The effluent DOMC fractions were monitored by ultraviolet (UV)‐visible (Vis) light and fluorescence spectroscopy. The results showed that the molecular weight (MW) of the effluent DOM approached that of the influent DOMC fractions with the injection of DOMC fractions. Three‐dimensional fluorescence excitation emission matrices (3D‐EEMs) coupled with parallel factor analysis resolved three fluorescent components, that is, low MW UV humic‐like substances (C1), high MW UV humic‐like substances (C2), and protein‐like substances (C3). The mobility of HAC and FAC decreased with increasing KCl concentrations (1 mM–50 mM), implying that electrostatic interaction was an important mechanism for the retention of DOMC in soil columns. The fact that the mobility of DOMC fractions in the black soil was greater than that in the red soil could be attributed to the high free Fe oxide content in the red soil. The retained DOMC fractions did not entirely desorb by the background electrolyte solution, suggesting that a part of the DOMC fractions retained in soil columns was strongly bound. These results are helpful in understanding the fractionation and transport of DOMC in soil environments.

Investigation of The Effect of Temperature and Contamination on Properties of Saturated Salt-Base mud

The most difficult challenge that can be encountered when drilling a salt section is the difficulty of controlling the change in drilling fluid properties. In addition, the challenging geological environment was encountered. , creep behavior, slim hole drilling in salt formation have a few traits: high soluble, wash out salt section (1). The treatment did by using drilling mud that inhibits changes and is resistant to contaminants. Sodium chloride and potassium chloride brine were used to create a new mud for discussing this research, following up on changes in the properties of the new mud, simulating the conditions of Salt section (12.25'' hole) in the Noor oil field. Moreover, In this investigation studied the effect of temperature and contaminants such as salt, shale and anhydrite on new mud properties (Rheological properties, Filtration, PH with Different concentrations of Kcl & Nacl. The results indicate that the dissolution of salt formation decreases with increasing KCl concentration up to 5% for saturating NaCl salt. This reduces the contaminant impact and increases the stability of mud characteristics.

Response of Ruellia simplex plants grown under water intervals and anti-transpirant treatments

Ruellia is herbaceous perennials are described as colorful groundcovers and it is very popular landscape plant cuttings of Ruellia plant were planted in pots. In the National Research Centre's greenhouse in Dokki, Giza, Egypt. A pot experiment was conducted in July 2020 and 2022 to examine the influence of KCl spraying and duration of irrigation on Ruellia plant growth and chemical contents. The current study compares the growth parameters of plants treated with KCl in three sprays at concentrations (0, 50 and 100 ppm) and water regime (3, 6 and 9 days) to those of control plants. However, increasing irrigation intervals for Ruellia plants there had no significant on growth parameters (plant height, branches number, root length, stem diameter and fresh and dry weight of shoots), while increasing irrigation intervals from 3days up to 9 days, increased flower number and delayed flowering. In addition, it is evident that N% was the highest by increasing irrigation intervals up to 9 days while P% showed a constant content, however the lower N% was recorded with the low irrigation intervals. Carbohydrate % as well as protein and photosynthetic pigments saved the same trend percentage. It can be concluded that, the increasing KCl concentration level up to 100 ppm caused an increase in previous mentioned vegetative growth parameters, flower number, flowering date, and chemical constituents (total chlorophyll, carbohydrate, protein%, carotenoids and mineral elements (N, P and K) concentrations compared with control and other KCl treatments. The purpose of this study is to learn more about the effects of KCl and water intervals on plant development and chemical components.

EFFECT OF POTASSIUM CHLORIDE ON GROWTH AND ACCUMULATION OF METAL MICRONUTRIENTS IN RICE SEEDLINGS GROWN HYDROPONICALLY

A greenhouse experiment was conducted to observe the effect of potassium chloride (KCl) on rice (Oryza sativa L. cv. Hitomebore). The plants were grown up to 14 days after treatments (DAT), with 0, 10, 20 and 30 mM KCl. It was observed that the rice seedlings were highly sensitive to KCl salinity, especially on producing toxicity symptoms and growth reduction. Iron concentration though increased significantly in shoot with increasing KCl concentration in the medium, it however, decreased in the root at the 30 mM KCl treatment. Manganese and Cu concentration decreased both in shoot and root at the 20 and 30 mM KCl treatments, however, Zn concentration decreased in shoot at the 20 and 30 mM KCl treatments. The concentration sensitivity of the metal micronutrients in shoot followed the general trends of Mn> Cu> Zn> Fe at the 20 and 30 mM KCl treatments. The K concentration increased as compared to the metal micronutrients with the increasing KCl in the medium.

Study on the Structure of a Mixed KCl and K2SO4 Aqueous Solution Using a Modified X-ray Scattering Device, Raman Spectroscopy, and Molecular Dynamics Simulation.

The microstructure of a mixed KCl and K2SO4 aqueous solution was studied using X-ray scattering (XRS), Raman spectroscopy, and molecular dynamics simulation (MD). Reduced structure functions [F(Q)], reduced pair distribution functions [G(r)], Raman spectrum, and pair distribution functions (PDF) were obtained. The XRS results show that the main peak (r = 2.81 Å) of G(r) shifted to the right of the axis (r = 3.15 Å) with increased KCl and decreased K2SO4. The main peak was at r = 3.15 Å when the KCl concentration was 26.00% and the K2SO4 concentration was 0.00%. It is speculated that this phenomenon was caused by the main interaction changing, from K-OW (r = 2.80 Å) and OW-OW (r = 2.80 Å), to Cl−-OW (r = 3.14 Å) and K+-Cl− (r = 3.15 Å). According to the trend of the hydrogen bond structure in the Raman spectrum, when the concentration of KCl was high and K2SO4 was low, the destruction of the tetrahedral hydrogen bond network in the solution was more serious. This shows that the destruction strength of the anion to the hydrogen bond network structure in solution was Cl− > SO42−. In the MD simulations, the coordination number of OW-OW decreased with increasing KCl concentration, indicating that the tetrahedral hydrogen bond network was severely disrupted, which confirmed the results of the Raman spectroscopy. The hydration radius and coordination number of SO42− in the mixed solution were larger than Cl−, thus revealing the reason why the solubility of KCl in water was greater than that of K2SO4 at room temperature.

The trade-off effect of KCl and NH4Cl on the hydrated structure in their mixed aqueous solutions

The hydrated structure of KCl and NH4Cl mixed solution were studied by X-ray scattering, Raman spectroscopy and molecular dynamics (MD) simulation method in the range of 0.00%-28.0% mass fraction at 25 °C. Through the analysis of reduced pair distribution function [G(r)], it was found that when the concentration of KCl in the mixed aqueous solution decreased and the concentration of NH4Cl increased, the main peak of G(r) shifted from r = 2.81 Å to the right of the axis. In the absence of KCl, the position of the main peak was r = 3.15 Å. It was speculated that this phenomenon was caused by the main interaction changed from K-OW and OW-OW (r = 2.80 Å) to NO (r = 3.06 Å) and NH4+-Cl− (r = 3.3 Å). It is indicated by the Raman spectra, when the concentration of KCl is high and the concentration of NH4Cl is low, the destruction of the tetrahedral hydrogen bond network in the solution is more serious. In the MD simulation, the coordination number of OW-OW decreases with the increase of KCl concentration, indicating that the tetrahedral hydrogen bond network is severely damaged, which is concerned with the results of Raman spectroscopy.

Thermal Stability, Optical Properties, and Gamma Shielding Properties of Tellurite Glass Modified with Potassium Chloride.

The synthesized glass system with a composition of (80-x) TeO2-10P2O5-10Nb2O5-xKCl mol% (where x = 5, 10, 15, 20, and 25) was successfully fabricated. The density (ρ) and molar volume (Vm) have been calculated. The investigated glasses were characterized using different analysis methods (differential thermal analysis (DTA) and UV-VIS-NIR spectroscopy). The radiation shielding effectiveness of the synthesized glass system was evaluated using different shielding parameters, such as mass and linear attenuation coefficients (MAC, LAC), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), and effective electron number (Neff). The results showed that with the increasing potassium chloride (KCl) concentration and decreasing tellurium oxide (TeO2) concentration, the density, refractive index, Urbach energy (Eu), and glass transition temperature (Tg) decreased, while the optical energy gap (Eopt) and thermal stability increased. As the KCl concentration increases, the values of MAC, LAC, and Zeff increase in the following order: TPNK5 % > TPNK10 % > TPNK15 % > TPNK20 % > TPNK25 %. Additionally, the shielding effectiveness of TPNK glass system showed good performance compared with some standard materials. The synthesized glass with a minimum KCl content has both good shielding effectiveness and good optical properties, in addition to reasonable thermal stability, which makes it suitable for shielding and optical applications.

Extraction of rubidium and cesium from a leach solution of lepidolite with biomass carbon adsorbents

Two biomass carbon adsorbents (BCA@PTS and CBCA@PTS) modified with potassium titanosilicate (PTS) were prepared by a hydrothermal deposition method and characterized by means of SEM-EDS, BET, FTIR, XRD, and XPS. The results show that the adsorbents have mesoporous structures, and potassium titanosilicate ((HK3)O2∙3SiO2∙4TiO2∙4H2O) was immobilized in the biomass carbon structure. The adsorption properties of these two adsorbents for rubidium (Rb+) and cesium (Cs+) from an aqueous solution and the tail liquor after extracting lithium from lepidolite were systematically studied. The adsorption amounts increased with increasing pH and decreased with increasing KCl concentration, which were mainly due to the competitive adsorption between H+ or K+ and Rb+ or Cs+ in solution. The adsorption kinetics of the adsorbents were consistent with the pseudosecondary kinetic model, which indicated that chemical adsorption played a leading role in the adsorption process. The adsorption capacities of Rb+ and Cs+ reached 2.57 mmol g−1 and 2.12 mmol g−1, respectively. The adsorption mechanism of Rb+ and Cs+ on the adsorbents was proposed as the ion-exchange between K+ in the adsorbents and Rb+/Cs+ in the solution. In addition, the adsorbents showed high extraction efficiency for Rb+ and Cs+ from two different lithium extraction tail liquors of lepidolite. Therefore, the obtained adsorbents in this work have excellent adsorption performance and show great potential as adsorption materials for Rb+ and Cs+.

Potassium isotopic fractionation during clay adsorption

Clay adsorption is a critical process responsible for the mobilization and cycling of potassium (K) on Earth’s surface. Recent studies emphasized the potential of using stable K isotopes (δ41K) to understand chemical weathering. However, the direction, degree, and mechanism of K isotopic fractionation linked to clay K uptake during chemical weathering remain poorly constrained.This work investigated the mechanism of K adsorption on clays (kaolinite and smectite) and the isotopic fractionation in three experimental sets with K-containing solutions. The time-series experiments revealed that the adsorption and isotope equilibria were attainedafter less than 12-hour reaction. Potassium adsorption rate slowed down and its isotopic fractionation approached the steady-state during 15-day reaction. The pH-dependent experiments demonstrated that the percentage of clay K adsorption and the isotopic composition of adsorbed K (and aqueous K) display negative linear correlations. Net isotopic fractionation between adsorbed and aqueous phases (Δ41Kad-aq) remained near-constant (0.6–0.8‰), regardless of variations in pH ranging from 4 to 10. The concentration-control experiments demonstrated that the percentage of K adsorption decreased with increasing KCl concentrations from 0.005 to 20 mM. The δ41K values of aqueous K reached the minimum of −0.53‰ after 92.7% K adsorbed (initial KCl of 0.005 mM). Potassium adsorption was substantially suppressed as ionic strength (fixed by Na+) increased from 0.001 to 0.5 M without apparent Δ41Kad-aq variations. The K K-edge XANES demonstrated that primary K incorporated in clay lattice and surface KCl derived from sorbed K+ and Cl− synchro-dehydration can be identified after drying of clays. These features indicate that adsorbed K+ was bounded onto clays as outer-sphere complexes, which can be replaced with excess Na+ at high ionic strength. Based on experimental results, we cannot distinguish specific mineralogy regulation on K isotopic fractionation. In sum, isotopically heavy K is preferentially sorbed on clay minerals. The results confirm an equilibrium fractionation path independent of reaction time, pH, ionic strength, and initial KCl concentration. Observed K isotopic fractionation is best fitted by an equilibrium isotopic fractionation law with a fractionation factor αad-aq of 1.00075. We highlight the opposite direction of K isotopic fractionation in clay adsorption and structural incorporation during chemical weathering, and their comparative contributions should be considered for future field investigations.

Effect of Electrolyte Composition and Concentration on Pulsed Potential Electrochemical CO2 Reduction

AbstractWith rising CO2 emissions and growing interests towards CO2 valorization, electrochemical CO2 reduction (eCO2R) has emerged as a promising prospect for carbon recycling and chemical energy storage. Yet, product selectivity and electrocatalyst longevity persist as obstacles to the broad implementation of eCO2R. A possible solution to ameliorate this challenge is to pulse the applied potential. However, it is currently unclear whether and how the trends and lessons obtained from the more conventional constant potential eCO2R translate to pulsed potential eCO2R. In this work, we report that the relationship between electrolyte concentration/composition and product distribution for pulsed potential eCO2R is different from constant potential eCO2R. In the case of constant potential eCO2R, increasing KHCO3 concentration favors the formation of H2 and CH4. In contrast, for pulsed potential eCO2R, H2 formation is suppressed due to the periodic desorption of surface protons, while CH4 is still favored. In the case of KCl, increasing the concentration during constant potential eCO2R does not affect product distribution, mainly producing H2 and CO. However, increasing KCl concentration during pulsed potential eCO2R persistently suppresses H2 formation and greatly favors C2 products, reaching 71 % Faradaic efficiency. Collectively, these results provide new mechanistic insights into the pulsed eCO2R mechanism within the context of proton‐donator ability and ionic conductivity.

Activated Carbons as Nanoporous Electron-Ion-Exchangers

The electrochemical, ion-exchange, sorption, hydrophilic-hydrophobic properties of several types of electrodes based on activated carbon (AC) and its porous structure are studied. By the method of standard contact porosimetry it is found that AC exhibits both hydrophilic and hydrophobic porosity and has the high specific surface area (600–2600 m2/g) which explains its use in supercapacitors and for capacitive deionization (CDI) of water. A new phenomenon of superhydrophilicity caused by swelling of surface groups (SG) in water is observed. The measurements of the AC surface conductivity show that even in pure water AC exhibits considerable ionic conductivity, which makes possible its use in the production of pure water by CDI. AC is shown to be an electron-ion-exchanger which is its unique feature. It is found that in addition to the electric double layer capacitance, the pseudocapacitance of redox-reactions of surface groups makes a substantial contribution into its total capacitance. The deep cathodic charging to negative potentials vs. reversible hydrogen electrode (RHE) in concentrated H2SO4 allows reaching the specific preudocapacitance of AC of 1100 F/g mainly due to the high pseudocapacitance of the reaction of hydrogen intercalation into carbon. This corresponds to the formation of a new compound C6H. In pure water, the specific capacitance of AC reaches 66 F/g and does not increase with the increase in KCl concentration, which suggests that this capacitance is associated with surface groups.

Effect of potassium chloride addition on soot formation during ethylene pyrolysis in a flow reactor

In this work, we investigated the effect of potassium chloride (KCl) addition on soot formation during ethylene pyrolysis in a flow reactor by using micro-orifice probe sampling in tandem with a series of systematic characterizations. The particle size distributions measured by a scanning mobility particle sizer showed that, with the addition of KCl, the nucleation of soot particles was not affected while the size growth of soot particles was inhibited. Then the morphology and mass of soot particles were examined by a transmission electron microscopy (TEM) and a centrifugal particle mass analyzer, respectively. The TEM images and mass-mobility relationship further showed that, soot particles were generally more compact and the primary particle size distributions were narrower when KCl was added. To understand what happened to the particle growth process, the charge characteristics were examined via tandem differential mobility analyzers. The number of particles with both double and triple positive charges was found to decrease with the increase of KCl concentration, indicating that the multi-charged particles were neutralized by KCl, which could lead to slower coagulation rates and thus smaller particles.

Oviductal high concentration of K+ suppresses hyperpolarization but does not prevent hyperactivation, acrosome reaction and in vitro fertilization in hamsters.

Mammalian sperm have to undergo capacitation to be fertilization competent. Capacitated sperm in vitro show hyperpolarization of the membrane potential. It has been reported that in mouse membrane hyperpolarization is necessary for the acrosome reaction. We recently found that the fluid of the hamster oviduct, where fertilization occurs, contained a high potassium (K+) concentration (~20 mEq/l). This high K+ concentration could depolarize the membrane potential and prevent the acrosome reaction/fertilization. Conversely, some beneficial effects on capacitation of high K+ concentration or a high K/Na ratio were also reported. In the present study, we investigated the effects of oviduct high K+ concentration on hamster sperm capacitation-associated events and fertilization. The present study confirmed that, in hamster sperm, membrane potential was hyperpolarized upon in vitro capacitation, indicating that capacitation-associated hyperpolarization is a universal phenomenon among mammalian species. An increase in KCl concentration in the medium to 20 mM significantly depolarized the membrane potential and suppressed hyperpolarization when in the presence of >101 mM NaCl. However, an increase in the KCl concentration to 20 mM did not significantly affect the percentage of motile sperm, hyperactivation or the acrosome reaction. No effect of 20 mM KCl on in vitro fertilization was observed. In addition, no correlative changes in hyperactivation and the acrosome reaction with K/Na ratio were observed. These results suggested that in hamsters the oviduct K+ concentration suppressed hyperpolarization but had no effect on capacitation and in vitro fertilization. Our results raised a question over the physiological significance of capacitation-associated hyperpolarization.

Enhancing mechanical properties of Electrospun Cellulose Acetate Fiber Mat upon Potassium Chloride exposure

Cellulose acetate (CA) based biomaterials are being used as substrates for bone ingrowth applications due to their non-toxic and non-irritant nature coupled with optimum morphology and stiffness. Electrospinning with additives and/or post-treatment has emerged as a viable protocol to improve the mechanical properties of CA further and expand its utility. Herein, we highlight the role of potassium chloride (KCl) in association with air-drying to enhance the elastic modulus and tensile strengths of CA fiber mats. Salt aggregation between fibers was observed through Scanning Electron Microscopy (SEM). However, Fourier-transform infrared (FTIR) analysis indicates the interactions between K+ ions and acetyl groups. X-ray diffraction (XRD) study suggests the retention of CA structure in the CA-KCl mats and the excess presence of KCl. The increase in KCl concentration (from 2 to 6%) boosts the elastic modulus to 176 MPa (52 times than pure CA) and tensile strength to 1.2 MPa (9 times than pure CA). Indeed, the presence of K+ ions offers osteoconduction to fiber mats, and thus the outcome has potential in bone tissue engineering.

Effect of K+ ion doping on structural and physical properties of PVA/MAA:EA polymer blend electrolytes

ABSTRACT A solid polymer blend electrolyte was prepared by using Polyvinyl alcohol (PVA) and Methacrylic Acid Ethyl acrylate (MAA: EA) polymers with different weight percentages (Wt%) of Potassium Chloride (KCl) by using solution casting technique, with water as a solvent. The structural, thermal, optical, and electrical properties of the prepared samples were studied. The X-ray diffraction pattern shows the decreasing trend in the degree of crystallinity due to the incorporation of KCl into the polymeric matrix. From the FTIR analysis, some peak intensities were decreasing and shifted in the case of KCl complexed films, which results in the complexation between the polymer blend and dopant ions. The TGA analysis reveals that the thermal stability of the KCl complexed films increases as dopant concentration increases. The SEM images reveal the structural reorganisation of polymer chains in the KCl complexed polymer blend electrolytes. UV-VIS spectra show that the optical constants such as absorption edge and band gap (both direct and indirect) values are decreased with an increase in KCl concentration. From conductivity data, it was noticed that the conductivity increased with the increase in the K+ ion concentration. The maximum ionic conductivity of 1.85 × 10−7 S/cm was obtained for the sample having 15 wt% of KCl salt.

Enhancing Mechanical Properties of Electrospun Cellulose Acetate Fibers Upon Potassium Chloride Exposure

Cellulose Acetate (CA) based biomaterials are being used as substrates for bone ingrowth applications due to their nontoxic and nonirritant nature coupled with optimum morphology and stiffness. Electrospinning with additives and/or post-treatment has emerged as a viable protocol to further improve the mechanical properties of CA and expand its utility. Herein, we highlight the role of potassium chloride (KCl) in association with air-drying to enhance the elastic modulus and tensile strengths of CA fibers. Salt aggregation in between fibers is observed through Scanning Electron Microscopy (SEM). However, Fourier-transform infrared (FTIR) analysis signifies the interactions between K+ ions and acetyl groups. The increase in KCl concentration (2 to 4 to 6%) boosts the elastic modulus to 176 MPa (52 times than pure CA) and tensile strength to 1.2 MPa (9 times than pure CA). The presence of K+ ions, indeed, offers osteoconduction to fibers, and thus the outcome has potential in bone tissue engineering applications

Electrolyte Concentration Variation during Pulsed Potential Electrochemical CO2 reduction to Control Product Selectivity

One of the grand challenges in electrocatalysis is to better understand the factors that determine activity and selectivity to control the precision of electrochemical reactions.1 Electrocatalytic CO2 reduction (eCO2R) is a prototypical example of such a reaction, where control over product selectivity would completely transform electrosynthesis processes. Beyond the pursuit of fundamentally understanding electrochemical catalysis, development of eCO2R is driven by growing concerns about global CO2 emissions and the quest for valorization of captured CO2. However, product selectivity and electrocatalyst longevity persist as obstacles to broad implementation of eCO2R. One possible solution to address this challenge is to apply a pulsed potential during eCO2R, which creates a stable reduction environment and tunable product selectivity.2 We leveraged this long-term product stability of pulsed potential eCO2R to examine the relationship between electrolyte concentration and composition with product selectivity for a copper electrode. Whereas constant potential experiments suffer from quick degradation as selectivity towards CO2 reduction products lasts only on the order of one hour, pulsing the potential maintains robust selectivity over 24 hours. This stability presents a unique opportunity to vary the electrolyte parameters while keeping experimental conditions consistent thereby eliminating electrode variability. We find the relation of electrolyte concentration and composition differs greatly for constant and pulsed potential eCO2R. In the case of constant potential eCO2R, increasing KHCO3 concentration is known to favor the formation of H2 and CH4. In contrast, for pulsed potential eCO2R, H2 formation is suppressed due to the periodic adsorption of surface hydroxides, while CH4 is still favored. In the case of KCl, increasing the concentration during constant potential eCO2R does not affect product distribution, mainly producing H2 and CO. However, during pulsed potential eCO2R, increasing KCl concentration suppresses H2 evolution and greatly favors C2 products, reaching 71% Faradaic efficiency. Collectively, these results provide new mechanistic insights into pulsed potential eCO2R in context of the ionic conductivity and higher presence of surface hydroxides which promote C-C bonding. More broadly, the techniques employed here can be used to understand and optimize other electrosynthesis processes.[1] Bell, A. T.; Gates, B. C.; Ray, D.; Thompson, M. R. Basic research needs: catalysis for energy; Pacific Northwest National Lab.(PNNL), Richland, WA (United States): 2008.[2] Kimura, K. W.; Fritz, K. E.; Kim, J.; Suntivich, J.; Abruña, H. D.; Hanrath, T., Controlled Selectivity of CO2 Reduction on Copper by Pulsing the Electrochemical Potential. ChemSusChem 2018, 11 (11), 1781-1786.