KOH Electrolyte Concentration Research Articles

Characterization of the aluminium-air battery utilizing a polypropylene separator with corrosion inhibition ability

Battery energy storage systems are widely used in modern electronic devices and electric vehicles. Metal-air batteries are among the electrochemical energy storage systems that provide high energy density and eco-friendly solutions. Aluminium-air batteries hold a significant advantage with their high theoretical specific energy and have the potential to replace lithium-ion batteries in the future. In this study, the electrical performance and corrosion inhibition characteristics of a polypropylene-based single and dual electrolyte system for aluminium-air batteries were investigated experimentally. The study revealed that a polypropylene separator can reduce the corrosion of the aqueous aluminium-air battery system by up to 40 %, improving the anodic utilization efficiency to 93 %. Electrochemical impedance spectroscopy analysis was used to characterize the single and dual electrolyte aluminium-air battery and propose equivalent circuit models. Compared to 1 M KOH electrolyte in a single electrolyte system, the solution resistance of a dual electrolyte aluminium-air battery was reduced by about 40 % using a combination of 1 M of KOH electrolyte and 1 M of H2SO4. This reduction is attributed to the enhancement of the oxygen reduction reaction at the air cathode. A high KOH electrolyte concentration will increase the corrosion of the aluminium anode but can improve the battery’s voltage. At 3 M KOH electrolyte, the plateau voltage is recorded at about 0.6 V while the discharge time reached 44 min when using aluminium alloy 6061 as the anode. The battery model developed in this work provides a fundamental basis for predicting the performance of aluminium-air battery packs.

Cathode Material Designing and Characterization: Co3O4/N‐doped Porous Carbon for Asymmetric Supercapacitors

AbstractMesoporous Co3O4/N‐PC in powder form was synthesized via a wet‐chemical approach, and the resulting material was deposited onto nickel foam as a substrate without the use of a binder. Prior to device fabrication, a thorough analysis of suitable and cost‐effective aqueous alkaline and neutral electrolytes was conducted. Electrolyte optimization was performed using Co3O4/N‐PC/NF electrode with Na2SO4, NaOH, LiOH, and KOH electrolytes. The supercapacitor performance of the binder‐free deposited materials was found to be superior in KOH electrolyte compared to other aqueous electrolytes at equal concentrations. Further optimization of the KOH electrolyte concentration was carried out to achieve the best electrochemical performance for the Co3O4/N‐PC/NF electrode. Electrochemical results demonstrated that the Co3O4/N‐PC/NF electrode performed well in 1 M KOH electrolyte, surpassing its performance at other concentrations. Subsequently, a solid‐state asymmetric device was fabricated, utilizing Co3O4/N‐PC, activated carbon, and a KOH+PVA gel as the cathode, anode, and electrolyte, respectively. The assembled asymmetric Co3O4/N‐PC/NF‐AC/NF device exhibited an energy density of 12.08 Wh kg−1 and a power density of 2500 W kg−1 within a potential window of 1.5 V. Impressively, after nearly 3000 continuous GCD cycles, the device showed negligible initial specific capacitance decay. The device was also successfully tested for powering the LED.

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.

Investigation of Performance of Anion Exchange Membrane (AEM) Electrolysis with Different Operating Conditions.

In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters-potassium hydroxide (KOH electrolyte concentration (0.5-2.0 M), electrolyte flow rate (1-9 mL/min), and operating temperature (30-60 °C)-were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings, the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration, 60 °C operating temperature, and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.

Aqueous rechargeable zinc air batteries operated at −110°C

•The concentration of KOH electrolyte and their freezing points is related •The lowest freezing point of the fabricated electrolytes is down to −120°C •An ultralow-temperature-tolerant FeCo-PC bifunctional electrocatalyst is developed •The zinc air battery exhibits high tolerance at ultralow temperature down to −110°C Zinc air batteries (ZABs) based on alkaline aqueous electrolytes using metallic zinc and air as electrodes have attracted significant attention for large-scale energy conversion systems. Nonetheless, the freezing of aqueous electrolytes and the catalytic performance deterioration in electrocatalysts hinder the ultralow-temperature operation of ZABs. Herein, we develop an ultralow-temperature-tolerant ZAB by fine-tuning the structure of the conventional KOH and developing an ultralow-temperature-tolerant FeCo-PC bifunctional electrocatalyst, which can endure the ultralow working temperature of a ZAB down to −110°C and exhibit an unprecedented battery performance with a maximum power density of 61.3 mW cm−2, capacity of 627.9 mAh g−1, and cycling stability of about 140 h at −70°C. This work represents a remarkable advance toward profoundly understanding the antifreezing properties of the conventional KOH electrolyte and the design of a low-temperature electrocatalyst, which will promote the development of ZABs with remarkably enhanced environmental adaptability. Zinc air batteries (ZABs) based on alkaline aqueous electrolytes using metallic zinc and air as electrodes have attracted significant attention for large-scale energy conversion systems. Nonetheless, the freezing of aqueous electrolytes and the catalytic performance deterioration in electrocatalysts hinder the ultralow-temperature operation of ZABs. Herein, we develop an ultralow-temperature-tolerant ZAB by fine-tuning the structure of the conventional KOH and developing an ultralow-temperature-tolerant FeCo-PC bifunctional electrocatalyst, which can endure the ultralow working temperature of a ZAB down to −110°C and exhibit an unprecedented battery performance with a maximum power density of 61.3 mW cm−2, capacity of 627.9 mAh g−1, and cycling stability of about 140 h at −70°C. This work represents a remarkable advance toward profoundly understanding the antifreezing properties of the conventional KOH electrolyte and the design of a low-temperature electrocatalyst, which will promote the development of ZABs with remarkably enhanced environmental adaptability.

Investigation of the discharging behaviors of different doped silicon nanowires in alkaline Si-air batteries

Compared with metal-air batteries, Si-air batteries have advantages on gravimetric/volumetric capacity and safety. This novel battery using flat Si wafer as anode has been preliminarily researched in recent ten years. In this work, Si nanowires (NWs) have been fabricated on p < 100 > and n < 100 > Si wafers and their discharging behaviors under various operating conditions have been systematically analyzed compared with flat Si wafer anodes. Si NWs anodes universally exhibit longer discharge times than flat Si wafer anodes because of their larger specific surface areas and superior resistance to the passivation caused by SiO2 deposition. It is also demonstrated that a KOH electrolyte concentration of 1.9 M is the lowest threshold for the p < 100 > Si anode at a current density of 0.03 mA/cm2, and the p < 100 > Si anode can discharge for more than 400 h. Furthermore, n < 100 > Si NWs anodes performed best with a discharge time of more than 500 h at higher current density of 0.05 mA/cm2 with an electrolyte concentration of 6 M. This work can aid in understanding the electrochemical properties of silicon anodes with different configurations and doping types in Si-air batteries and provide direction for the operation of Si-air batteries at appropriate conditions.

Facile Synthesis and Electrochemical Investigation of Undoped and Mn‐Doped ZnO Electrodes for the Energy Storage Application

AbstractIn the present investigation, the synthesis of zinc oxide (ZnO) and Mn‐doped ZnO thin film electrodes is reported for energy storage applications through spray pyrolysis technique. As‐prepared thin films are characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques for the crystal structural and morphological analysis, respectively. The XRD pattern shows substitution of Mn2+ in ion might have substituted Zn site without changing the hexagonal structure. The micrograph of pure ZnO thin films shows that the grains are agglomerated. The Mn‐doped ZnO thin film micrographs shows the spherical type morphology. The electrochemical study is carried for various concentrations of KOH electrolyte. The maximum specific capacitance of pristine ZnO and 5% Mn/ZnO is optimized at 3 M KOH electrolyte concentration. The pristine ZnO and M5Z electrode are exhibited 151 and 360 F g−1 maximum specific capacitance, respectively.

Flexible Self‐Powered Electrochemical Photodetector Functionalized by Multilayered Tantalum Diselenide Nanocrystals

AbstractFew layered transition metal dichalcogenides (TMDCs) are widely used in electrochemical systems due to their unique optical and electronic properties including applications over a large area. Despite the widespread use of 2D layered materials as active components of photoanode, electrochemical conversion studies of few‐layered Tantalum diselenide (TaSe2) are still negligible. In view of this, the TaSe2 nanocrystals (NCs) are successfully synthesized by using the facile liquid‐phase exfoliation (LPE) approach. Different physiochemical characterization confirms the inherent physical and optical properties of TaSe2 NCs. The flexible self‐powered photoelectrochemical (PEC) type photodetector based on TaSe2 NCs achieves the highest photocurrent density (Pph) of 20.8 µA cm−2 and photoresponsivity (Rph) of 0.208 mA W−1 in 0.5 m KOH. TaSe2 NCs demonstrate the excellent self‐driven ability and also unveil decent response under applied bias potential in different concentration of KOH electrolyte. Moreover, the electrode shows excellent ON/OFF switching stability up to 1000 s even after the 1 month of storage in the air. Importantly, the photodetector retains the Pph of 15.8 µA cm−2 after 95 bending cycles of 120° angle, displaying the great flexibility of TaSe2 NCs. This work demonstrates the potential of TaSe2 NCs for their extended application in PEC‐type devices and flexible electronics.

Probing the electrochemical properties of NiMn2O4 nanoparticles as prominent electrode materials for supercapacitor applications

NiMn2O4 (NMO) powders have been prepared by facile sol–gel route, and the effect of annealing temperature and the concentration of KOH electrolyte on its electrochemical performance has been investigated. The electrochemical performance of the NMO electrodes is tested via a three electrode arrangement in KOH electrolyte. The NMO electrode (NMO1) prepared from the powder synthesized at a temperature of 500 °C with an approximate crystallite size of 10 nm exhibits maximum specific capacitance of 571 Fg−1 at a scan rate of 5 mVs−1 in 1 M KOH electrolyte. The specific capacitance of the NMO1 electrode is found to be improved from 571 Fg−1 in 1 M KOH to 762 Fg−1 in 6 M KOH electrolyte. The improvement in the specific capacitance of the NMO1 working electrode in 6 M KOH electrolyte can be attributed to good electrochemical utilization and an effective charge storage mechanism.

Microfluidic Zinc-Air Cell

In this work, a microfluidic Zin-Air cell operated with a flow-through concept was constructed electrodepositing zinc on carbon paper electrodes by chronoamperometry. Additionally, chemically obtained α-MnO2 and Mn3O4 spinel were used as cathodes, and the cell performance was also compared with benchmarked Pt/C. Zinc electrodeposition time, flow rate, KOH electrolyte concentration and cathodic material were the variables herein evaluated. Zinc at 60 min was the best anodic material, and the maximum cell performance (~450 mW cm-2) was achieved at 4 M KOH and 3 mL h-1. α-MnO2 and Mn3O4 spinel presented half-wave overpotentials of 92 and 127 mV in contrast with benchmarked Pt/C, and during cell evaluation, these materials displayed power densities of 308 and 317 mW cm-2, respectively.

High Aspect Ratio Glass Micromachining by Multi-Pass Electrochemical Discharge Based Micromilling Technique

Fabrication of deep microchannels by a simple electrochemical discharge based multi-pass micromilling technique is reported. The effect of electrolyte concentration, tool feed rate, number of passes, and power supply on the geometric characteristics of the microchannel is presented. Numerical analysis was performed to predict the shapes and sizes of the microchannels, which matched quite well with the experimental values. An increment in the channel depth was observed with an increase in the machining voltage and the total number of passes. Through-channels were etched in a 400 μm thick glass substrate at machining voltages of 55 V and 60 V after the 6th and 5th pass respectively using a 10% KOH electrolyte. For deeper microchannels (>500μm), a higher electrolyte concentration, i.e., 30% was required, that had enhanced chemical etching, resulting in higher depth and relatively smooth channel surface. Microchannels having depth >1100 μm was obtained with a 30% KOH electrolyte concentration after the 16th pass. The number of passes required to achieve higher channel depth depends on the combined effect of voltage and the electrolyte concentration. The tool wear rate was higher at higher machining voltages. Moderate machining voltage, pulse frequency, and higher concentration are recommended for deep glass micromachining applications.

Effects of testing conditions on the performance of carbon-supported bifunctional electrodes

Carbon-based electrodes with a bifunctional catalyst are being studied extensively for use in rechargeable metal-air batteries. In this study, the effects of various testing conditions on the electrochemical performance, cyclic lifetime, and degradation mechanism of the electrodes prepared using the bifunctional La0.6Ca0.4CoO3 catalyst mixed with the graphitized Vulcan XC-72 carbon black and polytetrafluoroethylene were evaluated in detail. The electrochemical performance and total cycle life of the electrodes were not noticeably affected by the KOH electrolyte concentration or rest time between the charge/discharge. The charge/discharge current density used for the cyclic test significantly influenced both the total cyclic lifetime and degradation mechanism of the electrode. At the higher current densities (±50 and ± 100 mA/cm2), carbon corrosion led to electrode flooding and the loss of oxygen reduction capability while the oxygen evolution reaction occurring at the catalyst was largely sustained. At a lower current density (±6 mA/cm2), with periodic replacement of electrolyte to avoid carbonate formation in the electrode pores, the loss of the anodic catalytic ability of the bifunctional catalyst presumably via surface oxidation was clearly evident from the increase in oxygen evolution reaction overpotential. With the unchanged electrolyte, the electrode gas transport pore could be blocked by carbonate formation, leading to a decreased catalytic capability of the electrode for oxygen reduction. The failure modes of these electrodes under various cycling conditions were also assessed using impedance spectroscopy and inductively coupled plasma optical emission spectrometry.

Rational design of La0.85Sr0.15MnO3@NiCo2O4 Core–Shell architecture supported on Ni foam for high performance supercapacitors

To effectively enhance the energy density and cycling life of supercapacitors, we propose a novel strategy to use La0.85Sr0.15MnO3 as the core and encapsulated it with NiCo2O4 nanosheets to grow La0.85Sr0.15MnO3@NiCo2O4 (LSM15@NC) core–shell nanoflowers on Ni foam for the first time. Here, we systematically study the effect of KOH electrolyte concentration on the electrochemical behavior of LSM15@NC electrode. It manifests ultrahigh capacitance of 1341 F g−1 in 6 M KOH, which is around a threefold increase compared to that of 1 M KOH (400 F g−1 at 0.5 A g−1). Asymmetric supercapacitor assembled with activated carbon (AC) as negative electrode possesses remarkable performance with a wider work voltage of 1.8 V and maximum energy densities of 63.5 Wh kg−1 at a power density of 900 W kg−1. Even at ultra-high power density of 57600 W kg−1, it still retains high energy density of 25.2 Wh kg−1. Most importantly, it exhibits outstanding cycling life (retaining twice as much as the initial capacitance after 10,000 cycles), either as a single electrode or assembled asymmetric supercapacitor, much better than previously reported.

Corrosion Behavior of Highly As-Doped Oriented Si-Wafer Anodes in Alkaline Si–Air Batteries

One line of development to establish resource-efficient metal–air batteries is focusing on silicon materials as anode electrodes. While operation of primary Si–air batteries with ionic liquid electrolytes is one possible approach [1], employing conventional alkaline electrolyte is also considered by the recent investigations [2]. At the current state of development, the alkaline Si–air batteries suffer from high corrosion rates that reduce the theoretical specific capacity of 3820 mAh/g to 120 mAh/g [3]. Thereby, corrosion as being the major challenge has to be overcome in order to establish practical application of primary alkaline Si–air batteries. The objective of the present work is to investigate the corrosion behavior of highly As-doped <100> oriented silicon wafer anodes in alkaline solutions for a scope of conditions that may arise in battery operation. Firstly, the influence of the immersion times on the open-circuit corrosion rates are discussed in combination with the surface morphology development in 72 h. Secondly, the impact of KOH electrolyte concentration on the open-circuit corrosion rates is investigated and three ranges of KOH concentrations are identified with different limiting mechanisms. Moreover, basing on the electrochemical corrosion rates obtained from potentiodynamic polarization method, the comparison between the chemical and electrochemical corrosion mechanisms are pointed out. Further investigations are carried out on the corrosion behavior of Si wafers under anodic voltages as present during the discharge of batteries. The dependency of the discharge characteristics as the discharge voltage, corrosion rates, and mass conversion efficiencies on the KOH concentrations and current densities are analyzed and accordingly, optimum conditions for the battery application are discussed.

Investigation of the corrosion behavior of highly As-doped crystalline Si in alkaline Si–air batteries

High corrosion rate is one of the major obstacles that have to be overcome in order to establish practical application of primary alkaline Si–air batteries. At the current state of development the theoretical specific capacity of 3820 mAh/g is reduced to 120 mAh/g in long term operable alkaline Si–air batteries, with most of the capacity losses being due to corrosion reactions. In the present work the corrosion behavior of highly As-doped <100> oriented silicon wafers, that have proved stable performance as anode materials is summarized for a scope of conditions that may arise in battery operation. More specific, corrosion rates are presented and discussed with respect to (i) time dependence, (ii) influence of KOH electrolyte concentration, (iii) chemical vs. electrochemical corrosion, and (iv) corrosion under anodic potentials as present during the discharge of batteries. Corrosion rates were found to exhibit stable time profiles for immersion times longer than 8 h. With respect to concentration dependence, three ranges of KOH concentrations were identified. Within each range, the corrosion behavior is governed by similar mechanisms, but different limiting factors. Potentiodynamic measurements show that large part of the corrosion is chemical in nature. Under discharge conditions corrosion increases whereby the discharge potential, corrosion rates, and mass conversion efficiencies depend on KOH concentrations and discharge current densities.

Simple electrochemical preparation of nanoflake-like copper oxide on Cu-plated nickel foam for supercapacitor electrodes with high areal capacitance

Herein, a simple and green two-step electrochemical method was used to prepare nanoflake-like CuO\Cu microparticles on Nickel Foam (NiF) for supercapacitor applications. First, Cu microparticles were plated on NiF through a simple immersion method. Next, the Cu/NiF electrode was electrochemically oxidized in KOH solution to CuO/Cu/NiF. The effect of KOH electrolyte concentration on the electro-oxidation of Cu/NiF was also investigated. FESEM studies show that the surface morphology of CuO/Cu is highly porous, consisting of Cu interconnected microparticles on which islands of CuO have grown. The CuO/Cu/NiF electrode exhibited a high areal capacitance of 0.31 F cm−2 at a scan rate of 10 mV s−1 with excellent stability over 1000 voltammetric cycles. The results in this study show the potential application of CuO/Cu/NiF as a low-cost high-performance positive electrode in Supercapacitors.

EFFECT OF LORENTZ FORCE ON HYDROGEN PRODUCTION IN WATER ELECTROLYSIS EMPLOYING MULTIELECTRODES

The aim of this study was to investigate high-efficiency hydrogen production through water electrolysis by using multiple electrodes; the investigated approach can be applied in industry. In this study, three groups of parallel electrodes were used to conduct experiments and research related to water electrolysis parameters. During electrolysis, we introduced Lorentz forces to an electrolytic cell to determine whether the multielectrode mode is identical to the single-electrode mode regarding increases in hydrogen production. The results showed that a multielectrode group instantly increased gas production. In addition, introducing an external upward magnetic field into an electrolytic cell increased gas production at various concentrations during electrolysis. A downward magnetic field increased gas production in a 10- wt.% KOH electrolyte; this phenomenon does not occur in single-electrode electrolysis. According to IV curves, the decomposition voltage of the electrodes was between 1.87 and 1.93 V. A high-speed camera was used to photograph the magnetic flow field, gas-bubble-layer thickness, and the rising speed of the gas bubbles with and without a Lorentz force. An upward Lorentz force (FL(up)) improved all electrolysis effects, increased the gas bubble layer thickness, and increased the rising speed of the gas bubbles. The current difference increased to a maximum of approximately 370 mA/cm^2 when an electrode spacing of 5 mm and a 10-wt.% KOH electrolyte were used. Applying an FL(up), a KOH electrolyte concentration of 20 wt.%, and an electrode spacing of 3 mm increased the hydrogen gas yield by between 2.4% and 4%, according to the amount of accumulated gas measured using gas mass flow.

Al/Air 연료전지의 출력특성에 미치는 KOH 전해질과 H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; 감극제의 영향

The effects of additive such as H₂O₂ in KOH electrolyte solution for the Aluminum/Air fuel cell were investigated with regard to electric power characteristics. The power generated by a Al/Air fuel cell was controlled by the KOH electrolyte solution and H₂O₂ depolarizer. Higher cell power was achieved when higher KOH electrolyte concentration and higher H₂O₂ depolarizer amount. The maximum power was increased by the increase amount H₂O₂ depolarizer, it was found that H₂O₂depolarizer inhibits the generation of hydrogen and the polarization effect was reduced as a result. Internal resistance analysis was employed to elucidate the maximum power variation. Higher internal resistance created internal potential differences that drive current dissipating energy. In order to improve the output characteristics of the Al/Air fuel cell, it is thought to be desirable to increase the KOH electrolyte concentration and increase the H₂O₂ addition amounts.

The Investigation of Porous Al&lt;sub&gt;X&lt;/sub&gt;Ga&lt;sub&gt;1-X&lt;/sub&gt;N Layers on Si (111) Substrate with GaN/AlN as Buffer Layer

High quality undoped AlxGa1-xN with high Ga composition was grown on Si (111) substrate, using GaN/AlN as the buffer layer, by plasma-assisted molecular beam epitaxy (PAMBE). The present work reports on the photoluminescence (PL) studies of porous AlxGa1-xN prepared by ultraviolet (UV) assisted electrochemical etching in a solution of 2 % concentration of KOH electrolyte under illumination of an UV lamp with 500 W power for 30 min. The optical properties of porous AlxGa1-xN sample was compared to the corresponding as-grown GaN. PL studies suggested that the porosity was capable of improving the lattice mismatch induced strain. Porosity induced PL intensity enhancement was found in nanoporous sample. The resulting nanoporous AlxGa1-xN display red-shifted PL spectra compared to the as-grown AlxGa1-xN. Appearance of the red-shifted emission is correlated with the development of highly anisotropic structures in the morphology.

Solvothermal Synthesis of Nanostructured Flakes α-Ni(OH)&lt;sub&gt;2&lt;/sub&gt; Microspheres for Electrochemical Capacitors

Nanostructured flakes α-Ni(OH)2 microspheres were successfully synthesized by a facile solvothermal method using sodium dodecyl sulfate as a soft template and urea as a hydrolysis-controlling agent. The obtained products were characterized by Thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Electrochemical properties studies were carried out using cyclic voltammetry, galvanostaitc charge/discharge method, respectively. The results exhibited that the α-Ni(OH)2 single electrode had high specific capacitance in KOH electrolyte. A maximum specific capacitance of the α-Ni(OH)2 single electrode was up to 2398F/g in 6M KOH electrolyte concentration with 0 to 0.4V potential at 4mA/cm2 current density. Furthermore, the effects of the heat treatment temperatures on the electrochemical capacitance of the α-Ni(OH)2 electrodes were investigated.