Potassium-ion batteries: Outlook on present and future technologies

The limited resources and uneven distribution of lithium stimulate strong motivation to develop new rechargeable batteries that use alternative charge carriers. Potassium-ion batteries (PIBs) are at the top of the list of alternatives because of the abundant raw materials and relatively high energy density, fast ion transport kinetics in the electrolyte, and low cost. However, several challenges still hinder the development of PIBs, such as low reversible capacity, poor rate performance, and inferior cycling stability. Research on the cathode is currently focused on developing materials with high energy density and cycling stability, mainly including layered transition metal oxides, polyanion compounds, organic compounds, etc. Anodes based on intercalation reactions, conversion reactions, and alloying with potassium are currently under development, and promising results have been published. This review comprehensively summarizes the research effort to date on the electrode material optimization (e.g., crystals, morphology, reaction mechanisms, and interface control), the synthesis methods, and the full cell fabrication for PIBs to enhance the electrochemical potassium storage and provide a platform for further development in this battery system. This journal i

Fundamental Studies of the Structure-Property Correlations of Na-ion and K-ion Storage in Non-Graphitic Carbon

Grid-scale energy storage systems are urgently needed to increase the flexibility and rigidity of the grid for modern society and take full advantage of the renewable green energy resources such as solar energy and wind energy. Na-ion batteries (NIBs) and K-ion batteries (KIBs) have been emerged as one of the most promising solutions for grid-scale energy storage systems. Unfortunately, graphite, which is the commercialized anode in LIBs, does not show meaningful capacity in NIBs, and it shows poor cycling performance in KIBs. Non-graphitic carbon materials have been shown promising electrochemical performance in NIBs and KIBs. However, due to the structural complexity of non-graphitic carbon, the structure-property correlations of non-graphitic carbon anodes for Na-ion and K-ion storage are still not well established. Therefore, in this thesis, I focus on understanding the structure-property correlations of Na-ion and K-ion storage in non-graphitic carbon and improving the Na-ion and K-ion storage performance of non-graphitic carbon anodes. There had been reports regarding the structure-property correlations of hard carbon anodes in NIBs, where discrepancies still exist. In addition, the capacity of hard carbon anodes in NIBs rarely reaches values beyond 300 mAh/g. Herein, in this thesis, we first applied POx doping on hard carbon to tune its structure, which increases its reversible capacity from 283 to 359 mAh/g. We observe the interlayer d-spacing of the turbostratic nanodomains is expanded and the defect concentration of the doped hard carbon is increased. The structural changes of hard carbon lead to enhanced plateau and slope capacity. Our study demonstrates that Na-ion storage in hard carbon heavily depends on carbon local structures, where such structures, despite being disordered, can be tuned toward unusually high capacities. Even though our above-mentioned results agree well with our early proposed model, the structure-property correlations of Na-ion storage in hard carbon is still not solidified. Furthermore, how defects affect the slope capacity and what types of defects are beneficial for the slope capacity is still not clear. Therefore, in our following work, we synthesized a series of well-controlled heteroatom doped hard carbons, namely, P-, S- and B-doped hard carbon, and non-doped hard carbon where they show consistently low surface area. We then comprehensively characterized these hard carbons’ structural features and electrochemical performance which allows us to reveal the mechanism of Na-ion storage in hard carbon. Our combined experimental studies and first principles calculations reveal that it is the Na-ion-defect binding that corresponds to the slope capacity, while the Na intercalation between graphenic layers is responsible for the low-potential plateau capacity. In addition, our computational results also revealed that too strong binding between Na-ion and defects will lead to irreversibility. The new understanding provides a new set of design principles to optimize hard carbon anode for Na-ion storage. In a recent work, guided by our proposed design principles, we synthesized a highly defective hard carbon by microwave heating a low-temperature (650˚C) pre-annealed hard carbon. After a brief microwave treatment, i.e., for 6 seconds, the reversible capacity of the hard carbon was increased from 204 to 308 mAh/g. The microwaved carbon retains a high extent of structural defects after microwaving the low-temperature annealed hard carbon. Such a defective structure exhibits a much higher slope capacity than conventional hard carbon with less low-potential plateau capacity which can reduce the safety concerns. The microwave heating of carbon represents a new direction for tuning structures of hard carbon. The rate capability of hard carbon has long been underestimated in prior studies that used carbon/Na two-electrode half-cells. Through a three-electrode cell setup, we discover that it is the overpotential of the sodium counter electrode that drives the half-cells to the lower cutoff potential prematurely during hard carbon sodiation, particularly at high current rates, which prevents the hard carbon anode from being fully sodiated. Hard carbon demonstrates a much better rate-capability in this three-electrode setup. In the last part of this thesis, we studied soft carbon as anode for K-ion storage. In this work, we synthesized a series of soft carbons (SCs) by the pyrolysis of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) at different temperatures. By using polyacrylic acid as the binder, SC obtained at 700˚C (SC700) shows the highest capacity of 354 mAh/g which is the highest capacity of non-graphitic carbons reported so far by accounting the potential between 0-2 V. More importantly, SC700 shows a better cycling stability than SCs obtained at higher temperature, where it is still worse than the cycling performance of hard carbons. Via combined experimental and computational studies, we generate mechanistic insights about the structure-property correlations of K-ion storage in soft carbons

Recent advances in cobalt based heterogeneous catalysts for oxygen evolution reaction

The future of the world energy lies in clean and renewable energy sources. Many technologies, such as solar cells, wind turbines, etc., have been developed to harness renewable energies in different forms of fuel. Amongst them, electrolysis of water to produce oxygen and hydrogen is one of the paramount developments towards achieving clean energy, which has attained significant attention due to its green and simple method for the production of fuels. In electrolysis of water, the half-reaction containing the oxygen evolution reaction (OER) is a reaction that is kinetically sluggish, which requires higher overpotential to produce O2, when compared to the other half-reaction, i.e. hydrogen evolution reaction (HER). Many electrocatalysts are studied extensively to be used in the OER process to get an economical yield out of it. Noble metal-based catalysts are the state-of-the-art catalyst used for OER currently. But due to their high cost and scarcity, they cannot be applied in a large-scale manner to be used in the future. The non-noble metals (transition metals and perovskites) are gaining interest by exhibiting on par or better OER performance compared to the noble metal used. Due to their low cost, ample resources, and several metals available, they have opened up a variety of areas with a different combination of metals to be used as a catalyst for OER. Amongst these metals, cobalt has received massive appreciation for performing as an excellent OER catalyst. Multi metals, multimetal mixed oxides, multimetal phosphides, perovskites, and carbon-supported catalysts containing cobalt have shown low overpotential with high long-term stability. Therefore, in this review, we go through different cobalt-based electrocatalysts for OER, the general mechanism governing the OER process, the challenges that we are facing today to enhance the catalytic performance, and future aspects to overcome such challenges.This study was supported by the NPRP grant ( NPRP8-145-2-066 ) from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. The author(s) would also like to acknowledge the support from Qatar University 's internal grant QUCG-CENG-19/20-7 .Scopu

Beyond Lithium-Ion Technology: Lithium-Sulfur and Potassium-Ion for Better and Cheaper Batteries

Large-scale energy storage is one of the key components to power a sustainable future. While lithium-ion batteries (LIBs) have revolutionised our modern lifestyles, the cost of lithium resources and limited energy density that can be safely accessed have limited their potential as large-scale energy storage systems. Lithium-sulfur batteries (LSBs) and potassium-ion batteries (KIBs) are studied as the alternatives due to the high energy density sulfur and cheaper potassium. In the first part of this PhD project, metal oxides are in situ integrated with conductive and flexible carbon framework as the LSBs interlayer, for the first time, to mitigate active material loss. The composite prepared has a large TiO2 content that can chemically trap polysulfides and a high porosity CNF scaffold for physically hosting the polysulfides. The combined results in the interlayer increase initial discharge capacity and prolong the cycle life as compared to the cell without this interlayer. In the next part of this PhD project, a new ion storing mechanism is designed to compete for the diffusion limitation and the structural deterioration of KIB electrodes. Unlike a rigid oxide electrode, the oxygen deficient loose-layered potassium titanates (LL-KTO) anode delaminates and restacks reversibly upon charging and discharging, to name it, stacked ↔ sliced structural transformation. This mechanism allows for large storage of K+ ions in the electrode with net-zero structural deterioration during cycling. Subsequently, layered sodium titanates (L-NTO) are prepared to examine whether stacked ↔ sliced structural transformation mechanism can be engineered in sodium-ion storage. Nevertheless, as evidenced by the electrochemical performances, L-NTO stored sodium with intercalation. The work conducted in this PhD project provided essential knowledge on methods for mitigating active material loss in a sulfur based battery and mechanism on how to efficiently store potassium.Studying Abroad Scholarship, Ministry of Education, Taiwa

Screen-Printed Stretchable Supercapacitors Based on Tin Sulfide-Decorated Face-Mask-Derived Activated Carbon Electrodes with High Areal Energy Density

\ua9 2024 The Authors. Published by American Chemical Society.In this work, tin sulfide nanosheets decorated on face-mask-derived activated carbon have been explored as electrode material for electrochemical supercapacitors. A hydrothermal route was employed to grow tin sulfide on the surface and inside of high-surface-area face-mask-derived activated carbon, activated at 850 \ub0C, to produce a hierarchical interconnected porous composite (ACFM-850/TS) structure. The presence of tin sulfide in the porous carbon framework exposed the surface active sites for rapid adsorption/desorption of electrolyte ions and ensured high utilization of the porous carbon surface. Furthermore, the porous ACFM-850 framework prevented the stacking/agglomeration of tin sulfide sheets, thereby enhancing the charge-transport kinetics in the composite electrodes. Benefiting from the synergistic effect of tin sulfide and ACFM-850, the resulting ACFM-850/TS composite exhibited an attractive specific capacitance of 423 F g-1 at a 0.5 A g-1 current density and superior rate capability (71.3% at a 30 A g-1 current density) in a 1.0 M Na2SO4 electrolyte. In addition, we fabricated a planar symmetric interdigitated supercapacitor on a stretchable Spandex fabric using an ACFM-850/TS composite electrode and carboxymethyl cellulose/NaClO4 as a solid-state gel electrolyte employing a scalable screen-printing process. The as-prepared stretchable supercapacitors displayed an ultrahigh energy density of 9.2 μWh cm-2 at a power density of 0.13 mW cm-2. In addition, they exhibited an excellent cyclic stability of 64% even after 10,000 charge-discharge cycles and 42% after 1000 continuous stretch (at 25% stretching)/release cycles. Such screen-printed interdigitated planar supercapacitors with activated carbon composite electrodes and a solid-state gel electrolyte act as promising low-cost energy-storage devices for wearable and flexible integrated electronic devices

Screen-printed stretchable supercapacitors based on tin sulfide-decorated face-mask-derived activated carbon electrodes with high areal energy density

In this work, tin sulfide nanosheets decorated on face-mask-derived activated carbon have been explored as electrode material for electrochemical supercapacitors. A hydrothermal route was employed to grow tin sulfide on the surface and inside of high-surface-area face-mask-derived activated carbon, activated at 850 °C, to produce a hierarchical interconnected porous composite (ACFM-850/TS) structure. The presence of tin sulfide in the porous carbon framework exposed the surface active sites for rapid adsorption/desorption of electrolyte ions and ensured high utilization of the porous carbon surface. Furthermore, the porous ACFM-850 framework prevented the stacking/agglomeration of tin sulfide sheets, thereby enhancing the charge-transport kinetics in the composite electrodes. Benefiting from the synergistic effect of tin sulfide and ACFM-850, the resulting ACFM-850/TS composite exhibited an attractive specific capacitance of 423 F g–1 at a 0.5 A g–1 current density and superior rate capability (71.3% at a 30 A g–1 current density) in a 1.0 M Na2SO4 electrolyte. In addition, we fabricated a planar symmetric interdigitated supercapacitor on a stretchable Spandex fabric using an ACFM-850/TS composite electrode and carboxymethyl cellulose/NaClO4 as a solid-state gel electrolyte employing a scalable screen-printing process. The as-prepared stretchable supercapacitors displayed an ultrahigh energy density of 9.2 μWh cm–2 at a power density of 0.13 mW cm–2. In addition, they exhibited an excellent cyclic stability of 64% even after 10,000 charge–discharge cycles and 42% after 1000 continuous stretch (at 25% stretching)/release cycles. Such screen-printed interdigitated planar supercapacitors with activated carbon composite electrodes and a solid-state gel electrolyte act as promising low-cost energy-storage devices for wearable and flexible integrated electronic devices

Exploring heterometallic beta-diketonates for the low temperature synthesis of energy-related oxide and fluoride materials

In order to circumvent the issues associated with traditional ceramic methods such a

Resource Recovery from Industrial Wastewater through Microbial Electrochemical Technologies

There is currently a critical gap in knowledge regarding the application of microbial electrochemical technologies (METs) in industrial wastewater treatment and resource recovery. Resource Recovery from Industrial Wastewater through Microbial Electrochemical Technologies fills this gap by offering a comprehensive guide for researchers, students, and industry professionals interested in the field of microbial electrochemistry and industrial waste management. The book covers recent advancements in METs, focusing on their application in various industries to treat wastewater while recovering valuable resources, thus promoting sustainability. It provides an in-depth exploration of different industrial processes that generate wastewater, detailing the characteristics and quantities of effluents produced. The specifics of METs are also covered, including various configurations, electrode and membrane materials, microbial cultures, and catalysts used in these technologies. Additionally, the valuable resources that can be recovered through METs, such as biofuels, bioelectricity, and other commodity chemicals, are examined. This book serves as a practical guide for implementing METs in industrial settings, offering strategies to enhance the yield of recovered resources. It also offers insights into how these technologies can be integrated into existing industrial processes to achieve both economic and environmental benefits. Resource Recovery from Industrial Wastewater through Microbial Electrochemical Technologies is essential reading for research scholars, postgraduate students, and scientists working in the fields of microbial electrochemistry and industrial waste management. Industry professionals involved in research and development will benefit from the foundational knowledge and practical guidelines needed to implement METs in their industries. By bridging the existing knowledge gap, this book aims to advance the field of industrial wastewater treatment and contribute to more sustainable industrial practices

Amplified, Synergistic (Photo) Catalytic Water-Splitting by Thin- Film Conducting Polymer Composites

There is currently great interest in harnessing sunlight to generate hydrogen from water. Hydrogen may serve as a future energy carrier that could one day supplant fossil fuels like gasoline or diesel. One of the major challenges with implementing this concept is that, present-day photoelectrochemical (PEC) water splitting systems are either inefficient in their capacity to catalytically split water and/or subject to photocorrosion. The problem typically lies at the interface at which the water-splitting catalytic reaction occurs. One potential solution is to develop a thin-film, catalytic, interfacial layer that may lie between the photo-activated species (e.g. the semiconductor) and the aqueous, liquid phase. Such an interfacial layer could be designed to catalyse water-splitting at a more accelerated rate than is possible in its absence, whilst simultaneously suppressing photocorrosion. Ideally, such a thin-film interface would provide the greatest possible catalytic effect, preferably by synergistic amplification of the catalysis beyond what may be achieved by the catalyst species themselves. This work aimed to study and develop thin-film composites, based on well-known conducting polymer supports, that may serve as such an interfacial layer and that display synergistically amplified water-splitting catalysis. Despite their potential for facilitating high activity, thin-film conducting polymer supports have, historically, expedited only relatively weak performances in, for example, catalytic water oxidation (with current densities in the μA/cm2 range)