Redox flow batteries (RFBs) are promising for large-scale energy storage due to their modularity and long cycle life; however, their commercialization is limited by low power density and the high...

Herein, we have synthesized high-performance, low-cost ionomer biocomposites comprised of sulfonated poly(ether ether ketone) (SPEEK) and softwood Kraft lignin. Specifically, SPEEK ionomer composites containing renewably processed and fractionated low and...

Activated carbon (AC), generally synthesized from fossil fuels or biomass waste, is a crucial form of porous carbon used for the purification of gases and liquids. Its key performance metrics vary widely when produced from biomass because of the differing amounts of cellulose, hemicellulose, lignin, and mineral/ash content. In this study, we adapted the Aqueous Lignin Purification using Hot Agents (ALPHA) process, originally developed for purifying lignin-rich waste streams, to control the sugars (as cellulose/hemicellulose) and mineral/ash content of a given biomass. Biomass samples having a wide range of sugars (0.01-56 wt%) and mineral/ash compositions (0.01-7.1 wt%) were generated from a single, hybrid poplar cultivar and used to create AC using ZnCl2-impregnation and low-temperature carbonization. Strong correlations were developed between the biomass sugars and mineral/ash composition and the AC surface area, pore size, and pore distribution, with the maximum surface area of 2500 m2 g-1 being obtained from the precursor with the highest level (56 wt%) of sugars. These findings may provide a path to predicting the properties of AC from biomasses encompassing a wide range of compositions, and furthermore, select AC precursors for target applications.

Summary This study provides a detailed analysis of seismic interpretation techniques by moving from 2D to 3D Convolutional Neural Networks (CNNs). The study focuses on the effectiveness of these networks in interpreting salt bodies. The paper highlights the limitations of traditional 2D CNNs and showcases the improved spatial and contextual capabilities of 3D models enabled by the latest computing technologies. Our research compares model performances using a large dataset of 20 seismic surveys from the Gulf of Mexico and demonstrates significant improvements in accuracy and efficiency when using 3D CNNs.

Over the past decade, the production of biofuels from lignocellulosic biomass has steadily increased to offset the use of fuels from petroleum. To make biofuels cost-competitive, however, it is necessary to add value to the “ligno-” components (up to 30% by mass) of the biomass. The properties of lignin, in terms of molecular weight (MW), chemical functionality, and mineral impurities often vary from biomass source and biorefinery process, resulting in a challenging precursor for product development. Activated carbon (AC) is a feasible target for the lignin-rich byproduct streams because it can be made from nearly any biomass, and it has a market capacity large enough to use much of the lignin generated from the biorefineries. However, it is not known how the variability in the lignin affects the key properties of AC, because, until now, they could not be well controlled. In this work, various fractions of ultraclean (<0.6% ash) lignin are created with refined MW distributions using Aqueous Lignin Purification using Hot Agents (ALPHA) and used as precursors for AC. AC is synthesized via zinc chloride activation and characterized for pore structure and adsorption capacity. We show that AC surface area and the adsorption capacity increase when using lignin with increasing MW, and, furthermore, that reducing the mineral content of lignin can significantly enhance the AC properties. The surface area of the AC from the highest MW lignin can reach ~1830 m2/g (absorption capacity). Furthermore, single step activation carbonization using zinc chloride allows for minimal carbon burn off (<30%), capturing most of the lignin carbon compared to traditional burn off methods in biorefineries for heat generation.

Redox flow batteries (RFBs) are promising energy storage systems to support renewable energy sources and overcome the limitations imposed by their intermittent and unpredictable nature. As a developing technology, the cost of key components, namely the membrane, electrolyte, and electrodes, present a major hurdle to widespread integration. This work describes the performance of non-woven carbon fiber (NWCF) electrodes derived from low-cost petroleum pitch and produced using a scalable, inexpensive melt-blowing process. Compared to commercial polyacrylonitrile (PAN)-based carbon fiber felt, pitch-based carbon fibers have increased graphitic content, tensile strength, and electrical conductivity. Greenhouse gas emissions for pitch-based carbon fibers are estimated to be significantly lower than that of PAN-based carbon fibers. When RFBs with unoptimized NWCF electrodes are evaluated in zinc iodide electrolytes, the voltage and power density (83 mW cm-2) are slightly lower compared to RFBs with PAN-derived carbon felts (104 mW cm-2) @ 100 mA cm-2. RFBs fabricated with oxidized low-cost NWCF electrodes show nearly identical battery performance to those prepared with commercial PAN-derived carbon felts in vanadium electrolytes (peak power density of 137 mW cm-2vs. 139 mW cm-2, respectively). Because of their low-cost precursor and cheaper processing methods, NWCF electrodes offer a promising solution to reducing the cost of RFB electrode materials, and with further optimization, these electrodes will likely result in improved battery performance.

The zinc iodine (ZI) redox flow battery (RFB) has emerged as a promising candidate for grid-scale electrical energy storage owing to its high energy density, low cost and environmental friendliness. In this work, ZI RFBs were made with electrodes comprising carbon nanotubes (CNT) with redox-active iron particles, yielding higher discharge voltages, power densities, and 90% lower charge transfer resistances compared to cells with inert carbon electrodes. Analysis of the polarization curves reveals that cells with iron-containing electrodes have lower mass transfer resistances and 100% increase in power density (44 mW cm(-2) to 90 mW cm(-2)) at 110 mA cm(-2) relative to cells with inert carbon electrodes.

Sulfonated poly (ether ether ketone) SPEEK membranes with a degree of sulfonation of approximately 73 % were synthesized and investigated as the cation exchange membrane (CEM) for the zinc iodine (ZI) redox flow battery (RFB). Specifically, SPEEK was used in ZI RFB with 1 mol L-1 electrolyte and its performance was compared to the current benchmark CEM, NafionTM. Notably, columbic and energy efficiencies of 92.9 % and 75.9 %, respectively, were measured for the ZI battery with SPEEK at 17 mA cm-2, which was a 370 % increase in energy density compared to those with Nafion 212 membranes. RFBs with SPEEK exbibit a peak power density of 122 mW cm-2 at a current density of 166 mA cm-2 (98 mW/cm2 at 133 mA/cm2 with Nafion 212) because of their lower overpotential and higher discharge voltage. These results demonstrate the high cation selectivity of the SPEEK membranes in neutral, salt-based electrolytes, and provide the groundwork to develop a suitable replacement to Nafion for low-cost RFBs.

The power density of redox flow batteries (RFBs) utilized on iron‐containing electrolytes is improved by incorporating iron particle redox mediators into the electrodes. Nonpurified carbon nanotube (CNT) electrodes containing iron nanoparticles, formed during the synthesis of CNTs using the ferrocene−xylene process, are activated to create “hotspots” for faradaic energy storage that reduces losses associated with kinetical, ohmic, and mass transfer resistances. CNT electrodes are activated through cyclic voltammetry to initiate charge transfer interactions between redox electrolytes and iron nanoparticles in the electrode. RFBs with modified electrodes experience a 140% increase in power density and a 57% increase in energy density in coin‐cell configurations. Economic value and ready availability of iron paired with enhanced performance make iron RFBs a viable option for future RFB research. Herein, the highest peak power density yet reported for an iron‐based RFB at 180 mW cm −2 with iron‐modified electrodes under no electrolyte flow is demonstrated.

Rapid resource consumption and shifting public perspective on traditional electricity sources has forced the development of renewable energy sources, such as wind and solar energy. Redox flow batteries have become an important research area due to their independent power density and energy density, which is unique for electrochemical energy conversion and storage devices. These batteries are designed for grid-scale energy storage to be paired with wind and solar energy to create power grids that are not dependent on fossil fuels. The DOE has issued a 2023 target of 150 $/KWh and current all-vanadium chemistries approach these levels solely in vanadium costs. Therefore, other chemistries need to be developed that have long term stability, affordability, high performance, and utilize the high conductivity of water. Electrode doping facilitates charge transfer reactions at the electrode/electrolyte interface by improving the wettability and activity of the electrode to permit higher power and energy systems. These developments and inventive chemistries provide opportunities to employ cheaper chemistries to help meet the future demand for renewable energy. The recent developments in aqueous redox flow batteries utilizing chemistries other than vanadium are discussed in this review.

Thermal runaway is a major issue facing widespread adaptation of lithium-ion batteries. To achieve safe, thermally stable energy storage, various approaches have been proposed to regulate exothermic electrochemical reactions at high temperature, yet these have could only be either applied in aqueous systems or impractical in large-format cells. In this communication, we demonstrate that a copolymer, poly(2-chloroethyl vinyl ether-alt-maleic anhydride), or poly(CVE-MA), which exhibits a temperature-activated phase transition in organic solvents at high temperature, can be utilized as a thin film to inhibit lithium-ion migration/intercalation chemistries at the electrode/electrolyte interface. A large voltage drop and capacity decrease were observed at 80 °C due to interfacial hindrances imposed by the phase transition and resultant precipitation of poly(CVE-MA). This development of responsive polymers in organic solvents holds great potential for the future thermal safety of lithium-ion batteries.

Thermal runaway is posing big threat towards common electrochemical devices, such as lithium ion batteries and supercapacitors. It is caused by heat accumulated within electrochemical device and can cause devices to lose functionality, shorten service-life, or even cause hazardous fires and explosions. One effective approach to tackle thermal runaway is to break the electrochemical reaction Arrhenius thermal loop by introducing reaction inhibiting components into the system. Herein, through facile wet casting method, a temperature responsive polymer, poly( N -isopropylacrylamide) (PNIPAM) was cast into thin film and sandwiched in between polypropylene (PP) to make into a temperature responsive separator. It was found that once the temperature rose to 70 °C, instead of increasing in capacitance like in the control, PNIPAM-included batches decreased in capacitance. This capacitance reduction was mainly contributed by increased charge transfer resistance, which was caused by the sol–gel transition and precipitating PNIPAM chains residing upon PP membrane. A similar capacitance reduction was also observed for the ferricyanide redox system. Further investigation also revealed thicker PNIPAM films exhibited enhanced capacitance reduction and scan rate dependency. Temperature responsive polymer separators may prove to be an effective method to suppress high temperature electrochemical reactions and thus offer promise to reversible, thermally stabilized electrochemical devices. Graphical Abstract

Thermally stable electrochemical devices are ideal due to their stabilized performance and longer service life at extreme temperatures. However, ageing in supercapacitors, which is caused by generation of heat induced by high voltage, current, temperature, and aided by temperature induced self-accelerating reactions, plague the performance and lead to shortened service life. Poly(N-isopropylacrylamide) (PNIPAM) has been one of the most studied temperature responsive polymers (TRPs) in the past decades; it has a lower critical solution temperature (LCST) around 32 °C. By integrating PNIPAM into aqueous electrolyte, it was found that once LCST is reached, the specific capacitance of supercapacitors is reduced, which is accredited to drag of ion migration and precipitated polymer chains reside upon electrode surface. The capacitance reduction is even more obvious when the electrolyte solute changed into large size solute potassium ferricyanide. In terms of specific capacitance, comparing to an increase of the control, the PNIPAM integrated systems experienced a decrease under 70 °C. The integration of TRPs into electrochemical systems offers alternative approach to suppress high temperature capacitive reactions and ageing, thus could guarantee longer service life, performance stabilized supercapacitors.

Electrochemical performance of iron redox flow batteries (RFBs) was improved through incorporating iron redox mediators into the electrodes. Unpurified carbon nanotubes electrodes containing ferrocene catalysts, from the carbon nanotubes synthesis, are activated to create “hotspots” for Faradaic charge transfer that reduces losses associated with activation, Ohmic, and mass transfer resistances. This permits higher discharge voltages at elevated discharge currents, which from Ohm’s Law (P = iE) establishes augmented power densities. Carbon nanotube electrodes are activated utilizing cyclic voltammetry, in an acidic environment, to initiate charge transfer interactions between redox electrolytes and iron nanoparticles in the electrode. Modified electrodes exhibited 141% gain in power density and a 56.5% improvement in energy density in coin cell devices. Economic value and ready availability of iron paired with enhanced performance makes iron RFBs a viable option for future RFB research. The highest peak power density reported for all-iron RFBs to the author’s awareness was accomplished at 176 mW cm-2 with iron-modified electrodes under no electrolyte flow.

The advancement of novel materials to ameliorate interfacial charge transfer properties will drastically improve energy storage, heterogeneous catalysis, and various other electrochemical applications. Here we discuss a facile method that can utilize the Faradaic capabilities of residual iron nanoparticle catalysts that are captured within Multi-walled Carbon Nanotubes (MWNT) post-synthesis, thereby correcting the difficulties associated with creating hybrid nanocomposite electrodes. Non-purified MWNTs, experience a chemical oxidation procedure in an acidic environment with KMnO4 to partly “unzip” the MWNTs and reveal the redox-active iron nanoparticles to the electrolyte. A consistent redox peak affiliated with the Fe2+/3+ transition is achieved during the MWNT oxidation procedure yielding a ~350% improvement in capacitance (>300 F g-1) when compared to purified MWNT electrodes (70 F g-1). While these materials solely may be applicable as energy storage electrodes, the integration of redox species within an inert carbon electrode will also provide new opportunities to accelerate heterogeneous charge transfer reactions.

Redox Flow Batteries (RFBs) are an emerging electrochemical energy storage technology well-suited for intermittent energy sources, such as wind and solar. Integrated RFBs into grid-level energy systems would provide the storage necessary for alternative energy with only slight infrastructure changes. Currently, RFBs are limited by high material costs – from the use of precious metals – and/or low electrochemical activity. This work aims at improving power and energy of low-cost RFB electrolyte systems by doping carbon electrodes to facilitate Faradaic charge transfer at the interface, thereby decreasing costs and increasing accessibility of RFB systems. Carbon electrodes are modified with redox mediators to decrease the voltage drop and to increase charge transfer. Simulated half-cell experiments are conducted using carbon modified electrodes soaked with redox electrolytes s that are separated from pure base electrolytes by alkaline modified Nafion. Full cell testing is performed with modified Nafion separating the catholyte (0.7M Fe(CN)6 •3H2O and 1M NaOH) and the anolyte (0.35M Fe2SO4, 0.4M NaCl, Triethanolamine, and 3M NaOH). These electrolytes provide a test bed for evaluating all Iron RFBs as a cheaper alternative to Vanadium, therefore decreasing raw material cost and environmental impact. Incorporating redox mediators into carbon electrodes improves kinetics elevating voltage efficiency and allowing higher current densities without ebbing discharge voltage. Power is modeled with current and voltage by Ohm’s Law (P=IE). Electrolytes with low inherit voltage efficiency display increased energy density due to fully capturing the redox behavior at raised current densities. Our alkaline discharge voltage difference has a maximum of 1.5 V with our modified electrodes. These electrodes showed a ~10x increase in power with catholyte half-cell testing (305 to 32W/Kg) and a ~4x increase in power with the anolyte (990 to 227Wh/Kg). Energy density improvements were observed for the catholyte (232%) and the anolyte (41%), lowering the volume of electrolyte needed. Long term stability experimentation revealed consistent, coulombic and voltage efficiencies for 1400 cycles (~4 years of daily use). These adaptations to RFB electrodes could also be applied to current RFBs to increase their performance, thereby decreasing material costs and improving cheaper alternatives. Figure 1

Enzymatic cell disruption is a promising, highly energy-efficient technology for recovery of cellular compounds from microalgal cells, but it has not been applied at large scale because of its low cost-efficiency. In this work, we present a novel and highly efficient approach to enhance enzymatic disruption of Chlorella protothecoides cell walls to recover the lipid contents and cell wall compositional sugars. When thermoresponsive polymers, such as poly-(N-isopropylacrylimide-co-allylamine), were mixed with microalgal cell suspensions, cell disruption was increased from 22 to 68%, with equivalent increases in lipid recovery. The use of thermoresponsive polymers allows for simple and efficient separation of polymers after product recovery for reuse in subsequent batches. The highest cell disruption and associated lipid yield reached about 68% and 59%, respectively, which was achieved using 10mol-% amine copolymers with a loading of 0.05g/g algal biomass dry weight (BDW). During this process, about 50% of dry algal cell wall was converted to reducing sugars. Furthermore, we found that copolymers were able to disrupt algal cells in the absence of enzyme. Polymer loadings of 0.1g/gBDW led to the highest cell disruption and lipid recovery for 6h contact time reaching 32% and 30%, respectively. A quantitative and morphological analysis on polymer-enhanced microalgal cell disruption is presented, indicating that the polymer may function by stressing and breaking the cell wall and/or protecting enzyme from denaturation.

Nanoporous carbon materials are widely utilized in high-power supercapacitors due to their structural properties, chemical stability and conductivity, despite their limited energy density and charge storage capacity. Conducting polymers, on the other hand, possess high charge capacities; however, their application in commercial devices is hindered by degradation arising from their poor chemical and physical stability. Composites of carbon nanomaterials and conducting polymers have synergistic properties beneficial to supercapacitors, such as high capacitance and stability, but the limitations in scalable synthesis and polymer aggregation prevent widespread utilization. In this work, robust freestanding carbon nanotube (CNT)/electrically conducting polymer (ECP) electrodes are prepared using a simple dispersion filtration method, which can easily be scaled up. This process eliminates the use of binder, substrate or additional inactive weight. Composite CNT/ECP electrodes showed enhanced capacitance and charge capacity, achieving values up to 448 F/g and 84 mAh/g compared to 27 F/g and 10 mAh/g for pure CNT electrodes in aqueous electrolyte. Resulting symmetric cells exhibited energy and power densities of similar to 5 Wh/kg and similar to 283 W/kg, respectively, in aqueous electrolytes; and 12 Wh/kg and 744 W/kg, respectively, in organic electrolytes when using PEDOT/CNT electrodes. Given the process simplicity, relatively low cost and high throughput, the present composites have great potential for large-scale manufacturing of CP/CNTs supercapacitor electrodes. (C) 2016 Elsevier B.V. All rights reserved.