Effect Of KOH Concentration Research Articles

Exploring Two-Dimensional MOF-Derived Co/Ni Species for Efficient Electrocatalytic Hydrogen Evolution Reaction

Hydrogen evolution reaction (HER) has received a lot of attention due to its promising advantages in producing “green hydrogen” via electrocatalysis with low cost and high efficiency. Until now, developing transition metal-based electrocatalysts for HER has been a great challenge. In this regard, we reported a facile strategy to fabricate Co/Ni species encapsulated by carbon structure (CoNi@C) through annealing two-dimensional (2D) metal-organic framework (MOF) nanosheets. The CoNi@C that was prepared under 600 °C achieved the highest catalytic performance in 1.0 M KOH electrolyte with an overpotential of 330 mV to acquire 100 mA cm−2. In addition, the effect of KOH concentrations on the HER performance of CoNi@C-600 was explored. In 3.0 M KOH electrolyte, the current density of 100 mA cm−2 has been attained at a bias potential of 80 mV. The alkaline environment can improve the electrocatalytic performance and further enhance the stability of the as-prepared catalysts. This work would endow promising opportunities for manipulating MOF-based structures through pyrolysis to fabricate highly efficient electrocatalysts.

Quantification of Deleterious Phase Precipitation in a Hyper Duplex Stainless Steel Aged at 700-950 °C Using Optimized Linear Sweep Voltammetry: Effect of KOH Concentration

Quantification of Deleterious Phase Precipitation in a Hyper Duplex Stainless Steel Aged at 700-950 °C Using Optimized Linear Sweep Voltammetry: Effect of KOH Concentration

Preparation of porous biochar from fusarium wilt-infected banana straw for remediation of cadmium pollution in water bodies

The problem of cadmium pollution and its control is becoming increasingly severe issue in the world. Banana straw is an abundant bio raw material, but its burning or discarding in field not only causes pollution but also spreads fusarium wilt. The objective of this paper is to utilize biochar derived from the wilt-infected banana straw for remediation of Cd(II) pollution while to eliminate the pathogen. The activity of wilt pathogen in biochar was determined by PDA petri dish test. The Cd(II) adsorption of the biochar was determined by batch adsorption experiments. The effects of KOH concentration (0.25, 0.5 and 0.75 M) on the physicochemical characteristics of the biochar were also observed by BET, SEM, FTIR, XRD and XPS. Results showed that pristine banana straw biochar (PBBC) did not harbor any pathogen. The specific surface area (SSA) and Cd(II) adsorption capacity of 0.75 M KOH modified banana straw biochar (MBBC0.75M) were increased by 247.2% and 46.1% compared to that of PBBC, respectively. Cd(II) adsorption by MBBC0.75M was suitable to be described by the pseudo-second-order kinetic model and Freundlich isotherm. After Cd(II) adsorption, the CdCO3 were confirmed by XRD and observed through SEM. The weakness and shift of oxygen-containing functional groups in MBBC0.75M after Cd(II) adsorption implied that those groups were complexed with Cd(II). The results showed that pyrolysis could not only eliminate banana fusarium wilt, but also prepare porous biochar with the wilt-infected banana straw. The porous biochar possessed the potential to adsorb Cd(II) pollutants.

Theoretical Insights into the Effects of KOH Concentration and the Role of OH– in the Electrocatalytic Reduction of CO2 on Au

Theoretical Insights into the Effects of KOH Concentration and the Role of OH^– in the Electrocatalytic Reduction of CO₂ on Au

Effect of KOH Concentration on the Performance of HHO Generator at Varying Plate Surface Textures

In an effort to improve the performance of the HHO generator, the surface texture of the electrode plate has been introduced through this study. Optimization of the HHO generator’s performance has been developed continuously in many parts of the world. Therefore, the effect of KOH concentration on the performance of the HHO generator at different plate surface textures was investigated in this study. The HHO generator used in this study combines wet and dry cells. Generally, the results showed an increase in output current, HHO production rate, and output temperature, and conversely, a decrease in operating time due to the effect of increasing KOH concentration and different surface textures. The output current exhibits a significant increase of over 200% for all types of plate surfaces. For the output temperature, the smallest increase of about 9.7% is achieved by the linear plate surface. Meanwhile, the best HHO gas production rate is 267.26 L/min with an operating time of only 112.25 s, which occurred on the surface of the linear plate. Briefly, increasing the KOH concentration followed by modification of the plate surface has yielded better results compared to the plain surface. As for the surface texture, it causes a change in the plate surface area, which has a positive impact on the performance of the HHO generator.

Effect of KOH concentration on corrosion behavior and surface morphology of stainless steel 316L for HHO generator application

Hydrogen production could be enhanced by increasing the potassium hydroxide (KOH) concentration, but higher KOH concentrations result in higher corrosion rates. Therefore, a deep investigation of the electrochemical behavior of stainless steel (SS 316L) in the KOH solution is needed. This study investigates the influence of KOH concentrations on the electrochemical behavior, surface morphology, structure, and sample phases of SS 316L. The investigations were conducted by some electrochemical techniques, UV-vis, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The corrosion rate was found to increase, and solution resistance to decrease with increasing KOH concentration. Samples tested in 5, 30, and 50 g l-1 of KOH showed corrosion rates of 0.457, 2.362, and 5.613 µm year-1, respectively. A wide passive region and the noblest pitting potential were noticed for the sample with 5 g l-1 of KOH. Moreover, Mott-Schottky plots and characteristic wavelengths of UV-Vis suggest the formation of iron and chromium oxides by the passivation of samples. The SEM analysis showed a dynamic change of surface morphology from the lowest to the highest concentration with the intergranular corrosion found at the grain boundaries area. In conclusion, concentrations < 50 g l-1 KOH could be recommended since they would support the optimum remaining life of SS 316 L plates in HHO generators.

Effect of KOH Concentration on the Optical and Structural Properties of Perovskite CaZnO3 Thin films

A scanning electron microscope, X-ray spectrum, and UV spectrometer have been used in the examination of CaZnO3 perovskite thin films. Chemical Spry Pyrolysis (CSPD) technique was used in the preparation of the films from a mixture including different concentrations of KOH and a constant substrate temperature. The effect of KOH concentration was clear on the film’s transmittance, absorbance, and energy gap. The energy gap varied from 2.75 eV with 0.6 gm of KOH, up to 2.95 eV for 1.2 concentration, and finally, the energy gap became 3.1eV with 1.8 gm of KOH. In addition, the average grain size also decreased with KOH concentration, from 116 nm to 92 nm.

Parametric optimization and structural feature analysis of humic acid extraction from lignite

Humic acid (HA) is a complex organic compound made up of small molecules. A variety of raw materials are used to manufacture HA, due to which the structure and composition of HA vary widely. In this study, nitric acid oxidation of two coal samples from Lakhra (Pakistan) was followed by HA extraction using 2.5, 3.0 and 3.5% KOH solutions. The impact of different operating parameters such as; the effect of KOH concentrations, KOH-coal proportion, extraction time and pH range influencing the HA extraction efficiency was optimally investigated. Commercial HA applications possess numerous challenges, including valuable applications and sub-optimal extraction techniques. A significant limitation of conventional experimental methods is that they can only investigate one component at a time. It is necessary to improve the current processing conditions, this can only be achieved by modelling and optimization of the process conditions to meet market demands. A comprehensive evaluation and prediction of HA extraction using Response Surface Methodology (RSM) are also being reported for the first time in this study. The maximum HA extraction efficiency of 89.32% and 87.04% for coal samples 1 and 2 respectively was achieved with the lowest possible pH of 1.09 (coal sample 1) and 1(coal sample 2), which is remarkably lower as compared to those reported in the literature for conventional alkaline extraction process. The model was evaluated for two coal samples through the coefficient of determination (R2), Root Means Square Error (RMSE), and Mean Average Error (MEE). The results of RSM for coal sample 1 (R2 = 0.9795, RMSE = 4.784) and coal sample 2 (R2 = 0.9758, RMSE = 4.907) showed that the model is well suited for HA extraction efficiency predictions. The derived humic acid from lignite coal was analyzed using elemental analysis, UV–Visible spectrophotometry and Fourier-transformed infrared (FTIR) spectroscopy techniques. Scanning Electron Microscopy (SEM) was applied to analyze the morphological modifications of the extracted HA after treatment with 3.5% KOH solution. For agricultural objectives, such as soil enrichment, enhancing plant growth conditions, and creating green energy solutions, this acquired HA can be made bioactive. This study not only establishes a basis for research into the optimized extraction of HA from lignite coal, but it also creates a new avenue for the efficient and clean use of lignite.

Ternary NiCoFe nanosheets for oxygen evolution in anion exchange membrane water electrolysis

Tuning nickel-based catalyst activity and understanding electrolyte and ionomer interaction for oxygen evolution reaction (OER) is crucial to improve anion exchange membrane (AEM) water electrolyzers. Herein, an investigation of multimetallic Ni0.6Co0.2Fe0.2 OER activity, coupled with in-situ Raman spectroscopy to track dynamic structure changes, was carried out and compared to other Ni catalysts. The effect of KOH concentration, KOH purity, ionomer type, and electrolyte with organic cations was evaluated. The Ni0.6Co0.2Fe0.2 catalyst achieved 10 mA/cm2 at 260 mV overpotential with stability over 50 h and 5000 cycles in 1 M KOH. In-situ Raman spectroscopy showed that Ni0.6Co0.2Fe0.2 activity originates from promoting Ni(OH)2/NiOOH transformation at low potentials compared to bi- and mono-metallic nickel-based catalysts. Fumion anion ionomer in the catalyst inks led to a lower OER activity than catalysts with inks containing Nafion ionomer. The OER activity of Ni0.6Co0.2Fe0.2 is adversely influenced in the presence of fumion anion ionomer and benzyltrimethylammonium hydroxide (BTMAOH) with possible phenyl oxidation under applied high anodic potentials. The alkaline AEM water electrolyzer circulating 1 M KOH electrolyte, with a Pt/C cathode and a Ni0.6Co0.2Fe0.2 anode, achieved 1.5 A/cm2 at 2 V.

Effect of KOH concentration on the properties of ZnO nanoparticles

Of late, ZnO nanoparticles have been regarded as favourable material for designing highly sensitive and selective gas sensors owing to their striking and multifunctional features. A facile sol–gel process chemical technique was used in this study for the preparation of undoped ZnO nanoparticles. By deploying x-ray diffraction (XRD), transmission electron microscopy (TEM), UV–visible near infrared and photoluminescence spectroscopy (PL), we examined the optical attributes and structural characterisation of the undoped ZnO nanoparticles through a change in the concentration of the KOH solution. The typical peaks inspected in the XRD spectrum corroborate the wurtzite hexagonal arrangement in the undoped ZnO nanoparticles. Moreover, ZnO nanoparticles possess a non-agglomerated crystalline with spherical morphology, as acquired by TEM. In addition, the vibrational modes in FTIR spectra vary with the change of concentration of KOH solution in ZnO NPs. The Raman spectroscopic techniques were used to characterise the ZnO nanoparticles, which revealed their nanocrystalline nature.

In situ and operando thermal characterization in aqueous electric double layer capacitors using the 3[formula omitted] hot-wire method

The thermal properties of aqueous electric double layer capacitors (EDLCs) with KOH electrolytes were measured using the in situ and operando 3ω hot-wire method. The reversible entropy and free energy changes in the EDLCs caused dynamic changes in the effective heat capacity of the electrodes, which were monitored real-time during charge and discharge operations. In an EDLC with a 6 M KOH electrolyte, the effective heat capacities of the positive and negative electrodes with a varying voltage from 0 to 1 V were estimated to decrease by approximately 9.14% and 3.91%, respectively. This polarization dependence may be attributed to the capacitance capability, which is determined by the size of the adsorbed hydrated ions. Regarding the effect of KOH concentration, the maximal capacitance and change in effective heat capacity were observed in the vicinity of 8 M concentration, and attributed to changes in the thermodynamic state by the capacitance effect.

Transformation of Kaolin to Kalsilite: Effect of KOH Concentration and Reaction Temperature

Kalsilite was synthesized via a hydrothermal method using kaolin as a silica and alumina precursor and potassium hydroxide (KOH) as a potassium source. The effects of KOH concentration and reaction temperature were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated that kalsilite was formed as a result of the hydrothermal reaction of kaolin at 190 °C in 0.75 M KOH for 24 hours. Higher KOH molarity was found to increase the crystallinity of the product while 190 °C was sufficient to convert kaolin to kalsilite. However, zeolite W was the dominant product at lower KOH concentrations and temperatures.

Preparation of F-doped H2Ti3O7-{104} nanorods with oxygen vacancies using TiOF2 as precursor and its photocatalytic degradation activity.

Photocatalytic degradation is an eco-friendly and sustainable method for the treatment of water pollutants especially tetracycline hydrochloride (TCH). Herein, we developed F-doped H2Ti3O7-{104} nanorods with oxygen vacancies using TiOF2 as a precursor by simple alkali hydrothermal and ion-exchange methods. The phase structure, surface composition, optical properties, specific surface areas and charge separation were analysed by a series of measurements. The effects of KOH concentration on the structure and properties of H2Ti3O7 were investigated. It is confirmed that the TiOF2/H2Ti3O7 composite can be formed in low concentration KOH solution (1 mol L−1), while the H2Ti3O7 single phase can be formed in high concentration KOH solution (>3 mol L−1). The prepared F-doped H2Ti3O7-{104} nanorods provide a high specific surface area of 457 m2 g−1 and a macroporous volume of 0.69 cm3 g−1. The appropriate mesoporous structure of the photocatalyst makes TCH have a stronger affinity on its surface, which is more conducive to the subsequent photodegradation. Moreover, a synergistic mechanism of photosensitization and ligand–metal charge transfer (LMCT) in the photocatalytic degradation of TCH was proposed. In addition, the prepared F-doped H2Ti3O7-{104} nanorods showed excellent cycle stability and resistance to light corrosion. After five cycles of photodegradation, the degradation rate of TCH was only reduced from 92% to 83%. This low-cost strategy could be used for the mass production of efficient photocatalysts, which can be used for TCH clean-up in wastewater treatment.

Microporous activated carbons from lignocellulosic biomass by KOH activation

Oak wood samples were converted into activated carbons via chemical activation with KOH. The effects of KOH concentration and temperature on the yields and characteristics of the activated carbons were investigated; the yield of the activated carbons decreased with increased temperature and impregnation ratio. The lowest yield of activated carbon was obtained at the highest temperature (800 °C), with the highest KOH concentration of 100 wt%. The BET surface area of the activated carbons was comparable to that of commercially-activated carbon. The highest BET surface area of the activated carbon was 1662 m2.g−1, obtained at 800 °C with 50 wt% KOH concentration. KOH activation resulted in microporosity development in activated carbons.

Synthesis of ferroelectric 0.9KNbO3-0.1Ba(Nb1/2Ni1/2)O3-δ through one step hydrothermal reaction: Characterization and photocatalytic properties

0.9KNbO3-0.1Ba(Nb1/2Ni1/2)O3-δ (KBNNO) powder was synthesized through one step hydrothermal method at 200 ​°C. The effect of KOH concentration (1 M-18 M) and the effect of reaction time (30 min-12 ​h) on phase evolution and powder morphology were investigated. To get maximum perovskite phase atleast 10 ​M KOH concentration and 12 ​h soaking time were required. Characterization by X-ray diffraction, Raman spectroscopy, FESEM, TEM and XPS confirms the phase, structure, morphology and composition. The Powder morphology varies from spherical to irregular shape, to rod like nature, to cube shape when KOH concentration of the starting solution in the range of 4-6 ​M, 8-12 ​M and 14-18 ​M, respectively. UV–vis absorption spectroscopy indicates that KBNNO has significant absorption in the visible range compared to that of KNbO3. The photocatalytic degradation of Rhodamine B (RhB) shows an enhanced photocatalytic activity of KBNNO in comparison with KNbO3 synthesized under similar conditions. Finally, a mechanism for the enhanced charge separation and photodegradation is proposed.

Geopolymer Preparation from Bamboo Ash Containing Kaolin as Ash Fusion Control Agent

Bamboo is a prospective biomass fuel due to its high heating value and growth rate. The addition of kaolin is necessary in the thermal conversion of biomass to increase its ash fusion temperature (AFT), thus reducing fouling and corrosion of the combustion system. This study evaluates the feasibility of utilizing bamboo-kaolin co-processing residue for geopolymer synthesis. Thermochemical calculations suggest that bamboo culm ash liquidus increases by 15% by adding kaolin during combustion at a biomass to kaolin mass ratio of 95:5%. A 23 full factorial experiment measures the effect of activator Na2SiO3:KOH ratio, KOH concentration, and heat-curing period at 60 °C on the early strength of geopolymer mortars. Co-processing residue of bamboo-kaolin at a mass ratio of 95:5% produces geopolymer mortars with compressive strengths in the 10.7-40.3 MPa range. ANOVA treatment of the data indicate strong positive effect of KOH concentration. Crystalline phase characterizations indicate that the co-processing is able to convert kaolin to the amorphous, more reactive metakaolin. A shift in the IR absorption band from 1034 to 1008 cm-1 is attributed to the conversion of Si-O-Si bonds of the co-processing residue into Si-O-Al and Si-O-K bonds of the geopolymer gel phase. These results suggest the feasibility of geopolymerization as a waste valorization pathway to ensure the sustainability of the biomass-based energy production.

Effect of KOH Concentration on the Properties of Undoped Porous GaN on Sapphire Substrate Prepared by UV assisted Electrochemical Etching

Effect of KOH Concentration on the Properties of Undoped Porous GaN on Sapphire Substrate Prepared by UV assisted Electrochemical Etching

Rapid one-step preparation of hierarchical porous carbon from chitosan-based hydrogel for high-rate supercapacitors: The effect of gelling agent concentration

Herein, chitosan-based hydrogel beads (CHBs) were used to prepare N- and O-enriched hierarchical porous carbon (PC) by microwave heating for only 10 min. Water molecules in CHBs can act as heating carriers, and the resulting steam not only squeeze out air to create an oxygen-free atmosphere but act as physical activating agent to generate pores. Furthermore, the increased temperature contributed to form chitosan-based char, which, in turn, facilitated microwave absorption to further increase temperature. Considering that KOH as gelling agent of CHBs can also generate pores, the effect of KOH concentration on physicochemical properties of PCs was investigated in detail. Significantly, appropriately higher KOH concentration (3–7%) would cause fiercer reactions to achieve more developed porous structure, while excessive KOH concentration (10%) led to over-etching phenomenon and limited the further development on porous structure. The obtained PCs exhibited large specific surface area up to 1743 m2 g−1 and O, N-enriched structure (O: 25.1%, N: 4.9%). Particularly, the optimized PC-based electrode prepared by using 7% KOH solution showed remarkably high rate capability (89%). This work provides a one-step and cost-effective method to prepare a promising electrode material for high-rate supercapacitors.

Sustainable solidification of ferrochrome slag through geopolymerisation: a look at the effect of curing time, type of activator and liquid solid ratio

Ferrochrome (FeCr) slag was used as a precursor for the synthesis of a geopolymer. The effect of KOH concentration, liquid solid ratio (L/S), content of potassium metalisicate (KS) or potassium aluminate (KA), curing time on the unconfined compressive strength (UCS) and metal leachability of the synthesised geopolymer was investigated. A 10 M KOH and an L/S of 0.26 yielded a geopolymer with a UCS 13.0 MPa after 28 d of ambient temperature curing. A 0.125 wt KS:KOH addition yielded a geopolymer with a UCS of 14.7 MPa whilst a 1.25 wt KA:KOH addition yielded a geopolymer with a UCS of 24.5 MPa. The increase in strength was due to the formation of Calcium Silicate (Aluminate) hydrate. The aluminate activated FeCr slag geopolymer was the most competent of all geopolymers synthesised as it resulted in over 97% immobilisation of Fe, Zn, Mn, Ni and Cr. The 360-d static leachability tests for the aluminate activated geopolymer yielded a metal release rate lower than 90 mg mm− 2 of the geopolymer. The aluminate activated geopolymer also was resistant to changes in wet and dry cycles as it had a UCS reduction of 42% after 10 cycles whereas the pure FeCr slag geopolymer and the silicate activated geopolymer had a UCS reduction of 91 and 72% respectively after 10 cycles. The aluminate activated geopolymer met the minimum requirements for use as a paving brick for low traffic pavements. The study provides opportunities for sustainable use of FeCr slag with minimal environmental impact.

Preparation of Activated Carbon from Mangrove Waste by KOH Chemical Activation

In this study, Mangrove (Rhizophora mucronata) fruit waste which was generated from water-based extraction of natural dyes from this fruit was used as raw material in activated carbon preparation. Carbonization of chopped Mangrove fruit waste was conducted in a batch pyrolyzer for slow pyrolysis at temperature range of 300°C to 335°C and atmospheric pressure. The produced carbon was then soaked with potassium hydroxide (KOH) solution for 24 hours before activation process in an electrical furnace at 400°C for an hour. Effect of KOH concentration on physical characteristics of activated carbon was investigated in terms of moisture content, ash content, surface area, pore diameter, iodine number, and surface morphology. It was observed that the surface area and pore diameter increased with increasing the KOH concentration. Soaking the carbon in 2.5 M KOH provided the highest surface area and pore diameter of activated carbon, which were 1,920.6 m2/g and 5.52 µm, respectively. Also, the iodine number of 1,540.13 mg/g was obtained in correspond to the adsorption capacity.