Hydroxide Electrolyte Research Articles

Alkaline aqueous organic redox flow batteries of high energy and power densities using mixed naphthoquinone derivatives

Mixture of 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQ-S) and 2-hydroxy-1,4-naphthoquinone (Lawsone) is used as negative active species for aqueous organic redox flow battery (AORFB), while ferrocyanide (FeCN) is considered as positive active species in alkaline electrolyte. NQ-S is initially transformed to NQ-OH that has the same chemical structure with Lawsone by the nucleophilic attack under potassium hydroxide (KOH) electrolyte. The mixture of NQ-S and Lawsone (NQ-SO) has a higher solubility in KOH electrolyte (1.26 M in 1 M KOH) than the individual NQ-SO and NQ-S (0.42 and 0.83 M in 1 M KOH, respectively) because of the hydrophilic sulfite (–SO32−) groups eliminated from NQ-S over the transformation and the polar-polar interaction amid –SO32− group, organic species and KOH electrolyte. Lawsone to NQ-S ratio for optimal NQ-SO is 2:1, and this ratio is determined by the hygroscopic properties of –SO32− group. The cell voltage of AORFB using 0.6 M NQ-SO and 0.4 M FeCN is 1.01 V and its charge efficiency, discharge capacity, state of charge (SOC) and power density under 100 mA∙cm−2 are 99%, 23 Ah·L−1, 70% and 90 mW·cm−2. Furthermore, when the concentration of NQ-SO increases to 1.2 M (AORFB using 1.2 M NQ-SO and 0.4 M FeCN), its discharge capacity considerably increased to 40.3 Ah·L−1 with SOC of 83% and power density of 72 mW·cm−2.

Carbon electrodes derived from polyacrylonitrile-polyethylene glycol blend for high-performance supercapcitor

Continuous and evenly distributed porous carbon electrodes are prepared from electrospun nanofibers of Polyacrylonitrile (PAN) and Polyethylene glycol (PEG) blend with different weight ratio. Structure and surface morphology of carbon electrodes are characterized by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and Brunauer–Emmett–Teller method. The electrochemical performances of porous nanofiberous electrodes are studied by cyclic voltametry, galavanostatic charge-discharge and electrochemical impedance spectroscopy. The carbon electrodes derived from nanofibers of PAN/PEG blend with 15 wt% loadings of PEG shows excellent electrochemical properties with a high specific capacitance of 272.05 F g−1 at the current density of 0.5 A g−1 in 6 mol l−1 aqueous potassium hydroxide electrolyte. These electrodes show 92% capacity retention after 1000 charge/discharge cycles at the current density of 1 A g−1 .

Corrosion Inhibition of Magnesium by Anodizing In Safe and Unsafe Alkaline Electrolytes

Magnesium has high strength to weight ratio , good machinability , high creep stress and high impact resistance . Such properties make the magnesium an excellent choice in many applications . Disadvantages of magnesium represented in low corrosion resistance in most environments and ignites easily in air . Surface modification techniques which are used to improve surface properities of Magnesium are conversion surface treatments like chromating , phosphating , galvanizing electroplating such as Cu , Zn , Ni , Cr , electroless metal plating and cladding by Aluminum foil . Anodizing in an electrolyte (with pH>12) is considered a passivation process that produces chemical stable protective oxide film on magnesium surface . Usually unsafe electrolytes such as KOH are frequently used . Anodizing of commercial magnesium (ASTM 9980A) was carried out in 3M KOH(unsafe) , 1M Na2SiO3 and 0.6M K2SiO3(safe) electrolytes for time periods ranging from 10 to 50 minutes at constant voltage of 5V .The anode was magnesium specimen where the cathode was stainless steel type AISI 304 . Energy Dispersive X-Ray(EDX) and X Ray Diffraction (XRD) approved that magnesium Oxide (MgO) is the anodic film when using 3M potassium hydroxide electrolyte and a magnesium Silicate with a glassy morphology formed in the anodic film using safe electrolytes of 0.6M potassium silicate and 1M sodium silicate . Maximum film thickness reaches to 46 , 27,47 μm after anodizing at 30 min using 3M potassium hydroxide ,1M Sodium silicate , 0.6M Potassium Silicate respectively . It was found that the corrosion rate of commercially pure magnesium decreased from 37 to 7 , 2.2 , 1.3 mpy when using 3M potassium hydroxide , 1M sodium silicate , 0.6M potassium silicate respectively . At the same time the contact angle increases from 70 degrees to 114o, 105o , 113o degrees using the same electrolytes . An increase in microhardness of the anodic films was observed in 3M potassium hydroxide , 1M sodium silicate and 1M potassium silicate respectively . The adhesion of the anodic film measures according to ASTM D3359 method 13 for thickness <125 μm was classified in 3B which denote that the amount of the layer released by the adhesive tape lies from 5-15% of the formed layers using the three electrolytes.

Comparative study of anion exchange membranes for low-cost water electrolysis

Various anion-exchange membranes (AEMs) were studied in the electrolysis cell using the non-precious metal-based catalysts showing the good potential of selected AEMs in low-cost water electrolysis application. The 0.1–1 M potassium hydroxide electrolyte is applied for high performance electrolysis process, whereas the usage of pure water leads to the significant AEM resistance increase. The post mortem MEA analysis, using SEM is performed to study the structure and morphology of catalyst layers transferred from the electrodes prepared by catalyst coated substrate approach. The importance of the catalyst layer–membrane interface and the binder used to bond the catalyst layer is discussed. AEM electrolysis safety aspect in terms of the hydrogen crossover through the 28 μm thin A-201 membrane is studied. The linear dependency of the permeated hydrogen flux on current density is shown. Hydrogen content in the anode outlet gas is less enough to ensure high safety of the AEM electrolysis technology in the operating currents range.

Highly selective and efficient ammonia synthesis from N2 and H2O via an iron-based electrolytic-chemical cycle

Ammonia production via electroreduction of N2 and water under mild conditions is emerging as a promising alternative to the fossil fuels-reliance and CO2 emitting Haber-Bosch process. However, the achievement of high Faradaic efficiency and high ammonia formation rate is still challenging. Here, we demonstrate how ammonia can be selectively produced from N2 and H2O via a two-step iron-based cyclic process using a molten hydroxide electrolyte. The first step is the production of Fe by electrochemical reduction of Fe2O3. The second step is the steam-hydrolysis of Fe with bubbling N2 to produce NH3 and reform Fe2O3. Both reaction steps proceed isothermally at 250 °C in a molten salt electrolytic cell without switching of temperature and needing separation of the mediator, resulting in more easily putting into industrial practice. The cycle achieves an ultrahigh Faradaic efficiency of 79.8% at 1.15 V and a high ammonia formation rate of 1.34 × 10−8 mol s−1 cm−2 at 1.75 V. This is a critical advance in breaking the domination of hydrogen evolution reaction (HER) competition to achieve highly selective and efficient NH3 synthesis from N2 and H2O beyond reliance of fossil fuels.

Production of a NiO/Al primary battery employing powder-based electrodes.

This paper describes the use of aluminum and zinc as anodic materials for a battery employing nickel (II) oxide (NiO) as cathode. Comparison of both materials resulted in the development of a compact, cost effective, and easy to use primary NiO/Al battery employing an alkaline electrolyte. The system features electrodes composed of powder forms of the active materials on modified paper substrates that are contained in a simple multilayer design utilizing thin laminated plastic materials to provide structure and flexibility to the battery as well as a paper separator. Various concentrations of potassium hydroxide (KOH) electrolyte were examined and maximum performance was observed at 6M KOH. A maximum current density and power density of 1.94mA/cm2 and 1mW/cm2 , respectively was achieved. This user-friendly device was able to produce a maximum capacity of 2.33mAh/g when 2mA/g was applied. This work demonstrates the viability of a paper-based battery featuring powder electrodes as a possible power source for microelectronic devices.

Cover Feature: Undesired Bulk Oxidation of LiMn2O4 Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes (ChemPhysChem 22/2019)

Cover Feature: Undesired Bulk Oxidation of LiMn₂O₄ Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes (ChemPhysChem 22/2019)

Recent Advances in Solar Thermal Electrochemical Process (STEP) for Carbon Neutral Products and High Value Nanocarbons.

Climate change represents one of the most important environmental issues of our time. Due to high levels of anthropogenic CO2 emissions, atmospheric CO2 has for the first time ever exceeded 415 ppm and has increased from 315 ppm in 1950. An annual increase in atmospheric CO2 of ∼2 ppm is equal to a net increase of ∼15.6 billion tons of CO2. The combustion of fossil fuels for electricity and transportation is still the main reason accounting for the CO2 accumulation. On the top of that, fossil fuels are widely used in our modern industry for the productions of indispensable social staples. For instance, the millennia old thermal reduction of iron ore by charcoal or baked coal (3C + 2Fe2O3 → 4Fe + 3CO2) continues as the main method for the production of iron. The artificial fertilizer ammonia boosts the global population and is mainly produced from the Haber-Bosch process, in which hydrogen is generated via steam reforming of methane (CH4 + 2H2O → 4H2 + CO2). Sequestration and diminution of CO2 require the development of a portfolio of technologies on (1) efficient and long-term harvesting of renewable energy, that is, solar, not only for electricity but also directly as the energy force in vital chemical processes, wherever possible, (2) carbon-neutral processes to replace current industrial processes that emit vast amounts of CO2, such as iron and ammonia production, and (3) new, low-cost technologies for CO2 capture and conversion with particular interests in the exploration of CO2 as the feedstock for fuels or other valuable chemicals and materials. To this end, we conducted some studies on the sustainable synthesis of ammonia and iron with net-zero CO2 emissions and large-scale CO2 capture and conversion into fuels and high value nanocarbon products via electrolysis in molten salt(s) with the introduction of the Solar Thermal Electrochemical Process (STEP). In STEP, solar UV-visible energy is focused on a photovoltaic device that generates the electricity to drive the electrolysis, while concurrently the solar thermal energy is focused on a second system to generate heat for the electrolysis cell. The utilization of the full spectrum of sunlight in STEP results in a higher solar energy efficiency than other solar conversion processes. STEP has been applied to conduct (1) CO2-free ammonia synthesis from nitrogen and water with the aid of nano-Fe2O3 in a molten hydroxide electrolyte, (2) CO2-free production of iron via electrochemical reduction of iron ore in molten carbonate, (3) CO2 capture and conversion into nanostructured carbon products as well as fuels in molten or mixed molten electrolytes, and (4) organic electrosynthesis of benzoic acid from benzene without overoxidizing into CO2. In this Account, we highlight some recent achievements in these topics and propose that using STEP is a highly efficient strategy for saving energy and, consequently, the environment. STEP is an ideal tool that can theoretically be applied to all endothermic reactions.

Structural composite supercapacitor using carbon nanotube mat electrodes with interspersed metallic iron nanoparticles

A carbon nanotube (CNT) mat interspersed with metallic iron nanoparticles is investigated as a structural supercapacitor electrode material that could be incorporated into fiber-reinforced composites. Both ionic liquid and aqueous potassium hydroxide electrolytes are trialed to examine pseudocapacitive mechanisms and the long-term electrochemical stability of the CNT mat in symmetrical supercapacitors. High-resolution transmission electron microscopy showed the high level of interconnection of the CNTs and evenly distributed metallic iron nanoparticles, which enhances the structural and electrical performance of the electrode. Raman and X-ray photoelectron spectroscopies combined with thermogravimetric and surface area analyses are used to characterize the physico-chemical properties of the CNT mat and identify the different electrochemical mechanisms contributing to the supercapacitive behavior. Three electrode experiments demonstrated the relative contributions of the cathode and anode processes to the total capacitance. Symmetrical supercapacitor coin-cell trials used a structural glass-fiber separator and showed the ionic liquid electrolyte facilitated stable pseudocapacitance with the available iron nanoparticles, leading to specific energy and power as high as 18.3 Wh.kg−1 at 0.15 kW kg−1 and 5.6 Wh.kg−1 at 2.4 kW kg−1 after 5000 cycles. It is envisioned these materials can readily be incorporated into composite materials for structural energy storage technology.

Facile synthesis of a novel Fe3O4-rGO-MoO3 ternary nano-composite for high-performance hybrid energy storage applications

Supercapacitors (SCs) have been considered as inspiring energy storage devices due to the long cycle lifetime and high power densities. However, their energy density is limited due to the low capacitance of cathode materials and inferior cycling stability at practically useable potential windows >1.2 V. In this paper, we demonstrate the synthesis of a novel ternary Fe3O4-rGO-MoO3 nano-composite (FGM) with nanoparticles-like morphology (NPs) by utilizing the fast and facile microwave hydrothermal process. The optimized composition of FGM nanocomposite is characterized by the XPS, EDS, Raman, SEM, TEM and HRTEM techniques. The FGM-NPs supported on the carbon cloth (FGM@CC) electrode is used to investigate the electrochemical charge storage properties in basic potassium hydroxide (KOH) electrolyte. The charge-storage properties of the FGM@CC electrode were studied by the CV, GCD and EIS techniques. The obtained results of FGM@CC electrode in aqueous electrolyte showed excellent electrochemical performance as compared with single metal oxides: maximum specific capacitance of 1666.50 F g−1 (FGM@CC), 1075.26 F g−1 (Fe3O4 NPs) and 952.38 F g−1 (MoO3 NPs) at a current density of 2.5 A g−1. The capacitance retention was 95.01% (FGM@CC), 94.1% (Fe3O4 NPs) and 92.5% (MoO3 NPs) after 5000 cycles. Further, the charge storage mechanism is analyzed in the light of power's law and systematical investigated the capacitive and diffusion controlled based stored charge in FGM@CC electrode. Thus FGM nano-composite showed best performance as the cathode material for the next generation flexible supercapacitors.

Electrochemical investigation of novel reference electrode Ni/Ni(OH)₂ in comparison with silver and platinum inert quasi-reference electrodes for electrolysis in eutectic molten hydroxide

An efficient and green energy carrier hydrogen (H2) generation via water splitting reaction has become a major area of focus to meet the demand of clean and sustainable energy sources. In this research, the splitting steam via eutectic molten hydroxide (NaOH–KOH; 49–51 mol%) electrolysis for hydrogen gas production has been electrochemically investigated at 250–300 °C. Three types of reference electrodes such as a high-temperature mullite membrane Ni/Ni(OH)2, quasi-silver and quasi-platinum types were used. The primary purpose of this electrode investigation was to find a suitable, stable, reproducible and reusable reference electrode in a molten hydroxide electrolyte. Cyclic voltammetry was performed to examine the effect on reaction kinetics and stability to control the working electrode at different scan rate and molten salt temperature. The effect of introducing water to the eutectic molten hydroxide via the Ar gas stream was also investigated. When the potential scan rate was changed from 50 to 150 mV s−1, the reduction current for the platinum wire working electrode was not changed with newly prepared nickel reference electrode that designates its stability and reproducibility. Furthermore, increasing the operating temperature of molten hydroxides from 250 to 300 °C the reduction potential of the prepared nickel reference electrode is slightly positive shifted about 0.02 V. This suggests that it has good stability with temperature variations. The prepared nickel and Pt reference electrode exhibited stable and reliable cyclic voltammetry results with and without the presence of steam in the eutectic molten hydroxide while Ag reference electrode exposed positive shifts of up to 0.1 V in the reduction potential. The designed reference electrode had a more stable and effective performance towards controlling the platinum working electrode as compared to the other quasi-reference electrodes. Consequently, splitting steam via molten hydroxides for hydrogen has shown a promising alternative to current technology for hydrogen production that can be used for thermal and electricity generation.

Incorporating redox additives in sodium hydroxide electrolyte for energy storage device with the nickel cobalt molybdenum oxide active material

Abstract To enhance the redox reactions and improve the energy storage ability, redox additives have been widely incorporated in the electrolyte to assemble the battery supercapacitor hybrid (BSH). However, due to the possible generation of numerous redox reactions for the metal oxide with abundant redox states, it is limited to apply the redox additives in the multiple metal oxide system for producing more redox reactions and promoting the energy storage. In this study, two redox additives of p-phenylenediamine (PPD) and K3[Fe(CN)6] are incorporated in KOH electrolyte for fabricating BSH with the nickel cobalt molybdenum oxide active material. The addition of PPD in the electrolyte causes the reduction of the specific capacitance (CF) for the BSH, while the greatly enhanced CF value is obtained for the BSH applying K3[Fe(CN)6] as the redox additive in the electrolyte. With the optimized K3[Fe(CN)6] concentration in the electrolyte, the BSH shows the CF value of 3.13 F/cm2 at 10 mV/s along with the maximum energy density of 48.0 Wh/kg at 756.0 W/kg. The Coulombic efficiency higher than 95% and capacitance retention of 75% are obtained for the optimized BSH. This work firstly achieves the opposite results for the BSH with different sorts of redox additives in electrolyte. It is suggested that the ion size and the compatibility between the ions in the electrolyte and the pores in the active material are important to decide the capability for energy storage.

Fabrication of manganese oxide@nitrogen doped graphene oxide/polypyrrole (MnO2@NGO/PPy) hybrid composite electrodes for energy storage devices

The highly efficient hydrothermal chemical reaction was used to synthesis the manganese oxide@nitrogen doped graphene oxide/polypyrrole (MnO2@NGO/PPy) composites as a high capacitance electrode material for supercapacitors. The prepared composites structural and surface properties were confirmed by spectral and electron microscopic studies, respectively. The electrochemical cyclic voltammetric analysis carried out for MnO2@NGO and MnO2@NGO/PPy electrodes using potassium hydroxide electrolyte. The improved capacitance of 480 F.g−1 exhibited for MnO2@NGO/PPy hybrid electrode compared with 360 F.g-1 for MnO2@NGO electrode at 0.5 A. g−1 current density. The better cycling and rate retention properties exposed for MnO2@NGO/PPy hybrid electrode. Hence, the observed results suggested that MnO2@NGO/PPy electrodes offer promising uses for the high-performance supercapacitor.

Undesired Bulk Oxidation of LiMn2 O4 Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes.

Chemical and structural changes preceding electrocatalysis obfuscate the nature of the active state of electrocatalysts for the oxygen evolution reaction (OER), which calls for model systems to gain systematic insight. We investigated the effect of bulk oxidation on the overpotential of ink‐casted LiMn2O4 electrodes by a rotating ring‐disk electrode (RRDE) setup and X‐ray absorption spectroscopy (XAS) at the K shell core level of manganese ions (Mn−K edge). The cyclic voltammogram of the RRDE disk shows pronounced redox peaks in lithium hydroxide electrolytes with pH between 12 and 13.5, which we assign to bulk manganese redox based on XAS. The onset of the OER is pH‐dependent on the scale of the reversible hydrogen electrode (RHE) with a Nernst slope of −40(4) mV/pH at −5 μA monitored at the RRDE ring. To connect this trend to catalyst changes, we develop a simple model for delithiation of LiMn2O4 in LiOH electrolytes, which gives the same Nernst slope of delithiation as our experimental data, i. e., 116(25) mV/pH. From this data, we construct an ERHE‐pH diagram that illustrates robustness of LiMn2O4 against oxidation above pH 13.5 as also verified by XAS. We conclude that manganese oxidation is the origin of the increase of the OER overpotential at pH lower than 14 and also of the pH dependence on the RHE scale. Our work highlights that vulnerability to transition metal redox may lead to increased overpotentials, which is important for the design of stable electrocatalysts.

Efficient Electrocatalytic Synthesis of Ammonia from Water and Air in a Membrane‐Free Cell: Confining the Iron Oxide Catalyst to the Cathode

Ammonia is critical for food and chemical production; however, NH3 synthesis is one of the largest industrial greenhouse gas producers. We report a path to an exceptionally high rate (2.3 × 10–9 mol of NH3 s–1 cm–2), CO2 free NH3 electrosynthesis from H2O and air under ambient electrolysis conditions (60 °C, 1 atm). Iron oxide (dispersed in hydroxide electrolyte) catalyzed NH3 synthesis is probed at intermediate temperature (20–200 °C) and pressure (1–10 atm) with Monel mesh electrodes. Iron calcination preparation of the iron oxide catalyst is optimized by size, and then physically constrained to the reactive domain of the electrolysis cell cathode through use of mesh electrodes at even lower temperatures, allowing for an ambient, preferred electrosynthesis. These novel constraints enhance NH3 catalyst utilization at low temperature and open future pathways to the addition of ion‐specific membranes to the high rate NH3 synthesis cell.

Effect of Zn Addition on Electrochemical Performance of Al–Air Battery

We investigate the effect of Zn addition on an Al–air battery at the anode. The tested Al–air battery consists of a 6 mol% potassium hydroxide (KOH) electrolyte, a fiberglass separator, and a Pt/C + IrO2 cathode. The Zn-added Al(Al60Zn40)–air battery shows a higher power density of 48 mW/cm2, while a pure Al–air battery exhibits a power density of 38 mW/cm2. Approximately, 30 charge/discharge cycles of the Al–air battery were performed, while ~ 71 cycles of the Al60Zn40–air battery were performed. Adding Zn to the Al–air battery improves its electrochemical performance and the number of charge/discharge cycles can be significantly increased.

Hierarchical macro-/meso-/microporous oxygen-doped carbon derived from sodium alginate: A cost-effective biomass material for binder-free supercapacitors

Three-dimensional porous scaffolds doped with the heteroatoms show excellent performances in energy conversion and storage. Herein, we report a green synthesis approach to construct the oxygen-doped porous carbon electrodes by carbonizing the oxygen-rich biomass material, sodium alginate. By precisely controlling the carbonization temperature and increasing the mole ratio of α-L-guluronic acid units/β-D-mannuronic acid units in sodium alginate, the morphology, oxygen content and electrical conductivity of the as-obtained carbonaceous electrode are well balanced. This electrode material delivers capacitance of up to 424.6 F g−1 in 6 M potassium hydroxide (KOH) electrolyte at 1 A g−1, and good cyclic stability with the capacitance retention of >90% after 20,000 charge-discharge cycles. Such excellent electrochemical performance can be attributed to both the unique hierarchical macro-/meso-/microporous structure and the presence of abundant oxygen-containing functional groups in the as-prepared carbonized sodium alginate aerogels. The capacitance of our oxygen-doped porous carbon electrodes is at least twice greater than those of other carbonaceous electrodes produced from biomass precursors reported in literatures. This work provides a facile, effective and environmental-friendly approach for the fabrication of high-performance heteroatom-doped carbon-based electrodes for supercapacitor applications.

Machining of micro-holes on borosilicate glass using micro-electro chemical discharge machining (µ-ECDM) and parametric optimisation

ABSTRACTIn the present paper, an attempt has been made to machine micro holes on 500 µm thick borosilicate glass with 370 µm diameter Stainless Steel (SS) tool using Micro-Electro Chemical Discharge Machining (µ-ECDM). The machining parameters considered for the analysis are Voltage (V); Duty Factor (% DF) and Sodium Hydroxide (NaOH) Electrolyte Concentration (wt% C).The output responses are Material Removal Rate (MRR), Tool Wear Rate (TWR) and Radial Over Cut (ROC). Experiments have been conducted using Taguchi L16 Orthogonal Array (OA). Signal to Noise (S/N) ratio technique has been used to optimise the machining parameters for individual output responses. The optimised parameters for maximum MRR are 65 V, 35 wt% C, 65% DF resulted in 890 µg/min of MRR, for minimum TWR and minimum ROC, the optimised machining parameters are 50 V, 20 wt% C, 50% DF resulted in 25 µg/m of TWR and 50 V, 20 wt% C, 50% DF resulted in 10.16 µm of ROC. Further, the Grey Relational Analysis (GRA) technique has been used to optimise parameters and the obtained parameters are 50 V, 20 wt% C and 60% DF which resulted in 365 µg/m of MRR, 25 µg/m of TWR and 33.8 µm of ROC.Abbreviations:ANOVA, ANalysis Of VAariance; DF, Duty Factor; ECM, Electro Chemical Machining; EDM, Electro Discharge Machining; GRA, Grey Relational Analysis; GRC, Grey Relational Coefficient; GRG, Grey Relational Grade; MEMS, Micro-electromechanical system; MRR, Material Removal Rate; OA, Orthogonal Array; ROC, Radial Over Cut; SS, Stainless Steel; S/N, Signal to Noise; TA, Taper Angle; TWR, Tool Wear Rate; µ-ECDM, Micro-electro chemical discharge machining

Plasma-Treated, Nitrogen-Doped Nanoporous Carbon Cloth for High-Performance Supercapacitors Applications

Commonly used energy storage devices are majorly based on the commercial carbon cloth (CC) as a current collector due to its special features including ultra-low weights, three-dimensional (3D) structures, higher electrical conductivity with excellent porosities for the ion diffusion process. However, the poor compatibility and hydrophobic nature of the CC with the precursor solution and electrolyte is limiting the resultant electrochemical performance of the energy storage devices. To overcome this issue, in present work, we have developed the single step, facial nitrogen plasma method to induce nanostructuring over the CC, thereby significantly increasing the wettability and surface area of the CC, which both favourable for the facial electrochemical reactions. Morever, the plasma treatment induces the nitrogen doping on the surface of the CC allowed more electroactive species for electrochemical reactions. As a result, the nitrogen plasma treated CC (NCC) electrode shows excellent electrochemical feature for the supercapacitor application in the conventional potassium hydroxide (KOH) electrolyte. The NCC shows the highest specific capacitance of the 741 mF/cm2 at a current density of 0.5 mA/cm2, which is much higher than that of the untreated carbon cloth. In addition to this, the NCC shows the excellent cycling stability for 5000 charge-discharge cycles without any loss which represent the best capabilities of the nitrogen-plasma process for CC functionalization. The presented innovative approach of plasma process for the functionalization of carbon cloth may offer the new way to design and develop highly efficient carbon-based electrodes for supercapacitor applications.

Single-operation, multi-phase additive manufacture of electro-chemical double layer capacitor devices

Additive manufacturing (AM) may offer a flexible, cost-effective approach to address conventional manufacturing limitations, such as time-consuming, high work-in-progress, multi-step assembly. In principle AM can also allow more novel geometric or even bespoke designs of structural and functional products. However, in terms of energy storage devices such as batteries and supercapacitors, the benefits of AM have not yet been explored to any significant extent. In this paper, a hybrid-AM system, combining low-cost fused filament fabrication (FFF) and direct ink writing (DIW) techniques, has been designed to fabricate supercapacitors (electro-chemical double layer capacitors, EDLCs) in a single, automated operation. The inherent flexibility of the AM process provided an opportunity to address restrictions in geometric form factor associated with conventional planar supercapacitor manufacturing approaches. Functioning, ring-shaped EDLC devices were manufactured in a single, multi-material operation comprising symmetric activated carbon electrodes in a 1Μ potassium hydroxide (KOH) electrolyte hydrogel. Gravimetric and areal electrode capacitances were 116.4 ± 0.6 F g−1 and 599.2 ± 3.0 mF cm−2 at 10 mV s−1, with a columbic efficiency of 99.6 ± 0.4% in the as-printed condition. The work aims to accelerate progress towards monolithic integration of energy storage devices in product manufacture, offering an alternative fabrication process for applications with irregular volume/shape and mass-customization requirements.