Self-standing Electrode Research Articles

A π–d conjugated metal–organic framework decorated on a MXene-carbon nanofiber as a self-standing electrode for flexible supercapacitors

A c-MOF is grown on MX-CNF, which was prepared via electrospining method. Furthermore, it utilized for flexible supercapcitors with different flexibility angles.

One-step hydrothermal synthesis of a Ni3S2-FeMoO4 nanowire-nanosheet heterostructure array for synergistically boosted oxygen evolution reaction.

A key factor for boosting oxygen evolution reaction (OER) is the design of heterostructures with steerable defects and interfaces, which can optimize the surface electronic structures and achieve efficient water splitting to produce hydrogen fuel. Herein, we propose a novel one-step hydrothermal approach to fabricate hierarchical Ni3S2 nanowires with an S-doped FeMoO4 nanosheet heterostructure array in situ on Ni-Fe foam (NFF) as a self-standing electrode for synergistically boosted OER. The metalloid Ni3S2 nanowires with good conductivity support the FeMoO4 nanosheets and act as high-speed paths for the charge transfer. Numerous ultrathin S-doped FeMoO4 nanosheets are uniformly distributed on each Ni3S2 nanowire to form heterostructures with larger specific surface area and more revealable active sites, and a strong synergistic effect is created at the heterostructure interfaces to further promote the OER dynamics. Additionally, the NFF serves as the conductive support substrate and simultaneously provides the Ni and Fe sources for the self-growing Ni3S2-FeMoO4, leading to a structurally-integrated electrode with low contact resistance, fast mass transfer, and good stability. Therefore, the Ni3S2-FeMoO4/NFF electrode offers a low overpotential of 331 mV to achieve 500 mA cm-2 and long-term stability at 100 mA cm-2 level for more than 40 h. This work provides insight into the heterostructure of molybdate and sulfide, and a deep understanding of the significance of the synergism in OER operation.

All-Solid-State Li-Metal Cell Using Nanocomposite TiO2/Polymer Electrolyte and Self-Standing LiFePO4 Cathode

Li-ion batteries (LIBs) represent the most sophisticated electrochemical energy storage technology. Nevertheless, they still suffer from safety issues and practical drawbacks related to the use of toxic and flammable liquid electrolytes. Thus, polymer-based solid electrolytes may be a suitable option to fulfill the safety and energy density requirements, even though the lack of high ionic conductivity at 25 °C (10−8–10−7 S cm−1) hinders their performance. To overcome these drawbacks, herein, we present an all-solid-state Li-metal full cell based on a three-component solid poly(ethylene oxide)/lithium bis(trifluoromethanesulfonyl) imide/titanium dioxide composite electrolyte that outclasses the conventional poly(ethylene oxide)-based solid electrolytes. Moreover, the cell features are enhanced by the combination of the solid electrolyte with a self-standing LiFePO4 catholyte fabricated through an innovative, simple and easily scalable approach. The structural, morphological and compositional properties of this system are characterized, and the results show that the electrochemical performance of the solid composite electrolyte can be considerably improved by tuning the concentration and morphology of TiO2. Additionally, tests performed with the self-standing LiFePO4 catholyte underline a good cyclability of the system, thus confirming the beneficial effects provided by the novel manufacturing path used for the preparation of self-standing electrodes.

Elevating Energy Density in Li-Ion Batteries through Electrospun Nanotubular Titania-Polymer Interfaces

The introduction of new anode materials holds the potential to address critical safety concerns associated with current commercialized options in Li-ion batteries. Graphite, while widely used, poses challenges due to its low charging potential, which contributes to the growth of dendrites and safety risks. In contrast, titania-based materials present an appealing solution. Their higher operational potential not only curbs dendrite formation but also prevents the formation of a thick solid electrolyte interface (SEI). Furthermore, the limited volume expansion during lithiation significantly enhances their safety profile, differentiating them from graphite-based anodes such as those incorporating silicon.In this new study, titania-based nanotubular structures were created for high-energy Li-ion batteries using a novel electrospinning technique. Titania-based nanotubes were synthesized, modified for optimal charge transfer, and combined with a self-standing electrode through electrospinning with PVDF. The effects of various thermal treatment conditions on Li-ion diffusion were explored using electrochemical methods. The best charge transfer kinetics were observed in the sample treated for 10 hours. After optimizing the electrospinning process, a fully embedded nanotube fibrous structure was achieved, confirmed by electron microscopy. The use of a polymeric network removed the need for metallic current collectors, boosting energy density by 14%. These electrospun electrodes show great promise for high-energy applications.This work was supported by the M-era.Net 2019 call project “LiBASED Li-ion BAttery-SupErcapacitor Hybrid Device”. The research was co-funded by the Turkish Scientific and Technological Research Council (TUBITAK) with project number 119N758.

Step Potential Electrochemical Spectroscopy (SPECS) Technique to Investigate the Ageing of Carbon Electrodes in Organic-Based Electrochemical Capacitors

Current research on electrode degradation in electrochemical capacitors (ECs) mainly focuses on the application of new materials and the establishment of their stability on the basis of various standards and qualitative tests. However, there exists limited research that focuses on the elucidation and determination of the degradation mechanisms and pathways of carbon electrodes. The proposed study uses an innovative approach with the use of the Step Potential Electrochemical Spectroscopy (SPECS) technique, which allows one to quantify the contribution of different charge-storing mechanisms, and successfully track any changes that take place after accelerated ageing, including structural changes of the electrode in the organic medium. Additionally, the role of oxygen content on the degradation of ECs was explored.In this report carbon material, namely binder-free Activated Carbon Cloth (ACC) Kynol® 507-20 was prepared in a furnace under a nitrogen atmosphere at different temperatures, namely 120, 500, and 1000ᵒC. This is so that the effect of the presence of different oxygen functional groups on the surface of carbon could be investigated. The material was selected as a self-standing electrode to eliminate any influence the binder would have on the electrode porosity. Subsequently, these materials were prepared as electrode materials and assembled in a symmetric two-electrode setup with 1M TEABF4/AN (tetraethylammonium tetrafluoroborate in Acetonitrile solvent). In each cell, the potential range of both electrodes was first determined in a 2-electrode Swagelok® cell with RE using galvanostatic charge/discharge (1 A g-1). The further procedure involved 3 CV cycles (1 mV s-1) at a predetermined potential for each electrode in a 3-electrode set-up, followed by SPECS measurement where 5-minute potentiostatic hold with 10 mV potential steps was applied. The obtained current vs. time plots were used to calculate the corresponding capacitance, diffusion and residual parameters. Floating tests at 2.7 V were then carried out for each system. According to the international standard (IEC 62391-1), system failure is reported when the initial capacitance drops below 80% of its initial value; thus floating experiments were halted after that value was reached for each system or when the resistance of the cell doubled in value. The electrochemical investigation of the individual aged electrodes was then repeated in the same manner.Our study allowed for a thorough examination of individual electrodes prior to and after floating experiments, which helped to elucidate the degradation causes and pathways in organic medium.

Unveiling the morphological influence of nitrogen-doped carbonized wood anchored 3D transition metal oxide microarchitectures on catalytic activity: A trifunctional electrocatalyst for sensing and energy conversion

The rational construction and advancement of binder-free, self-standing, and cost-effective electrodes endowed with highly active trifunctional electrocatalysts represent a pivotal nexus between the research domains of energy and healthcare applications. However, the lack of proficient non-precious-metal trifunctional electrocatalysts bridging the aforementioned research domains remains a pinnacle barrier. Herein, we proposed distinct fabrication protocols to construct morphologically diverse three-dimensional (3D) CuO microarchitectures directly docked over the naturally inherited carbon channels of nitrogen-doped carbonized wood (NCW) (CuO@NCW) obtained by the carbonization of waste wood monoliths and explored the efficacy of different catalytic designs towards the trifunctional performances on non-enzymatic glucose sensing and glucose oxidation-assisted water splitting. Among the diverse binder-free engineered electrodes, CuO@NCW obtained via the facile electrodeposition (E) route (dubbed as CuO-E@NCW) demonstrated proficient electrocatalytic trifunctionality benefitting from the allied merits of the robustly anchored 3D porous dendritic architectures equipped with ample porosity and momentous interconnectivity. The as-fabricated CuO-E@NCW electrode as a glucose sensor displays two broad linear ranges between 0.01 and 0.5 mM and 0.5–4.0 mM with corresponding elevated sensitivities of 24.6 and 7.2 mA mM−1 cm−2, with a lower limit of detection of 0.0013 mM (S/N = 3). Besides, this best-performing electrode delivers a high current density of 50 mA cm−2 with a low cell voltage of 1.39 V in the glucose electrolysis system, which is 170 mV lower compared with stereotypical alkaline water splitting.

Self-Standing Porous Aromatic Framework Electrodes for Efficient Electrochemical Uranium Extraction.

Electrochemical uranium extraction from seawater provides a new opportunity for a sustainable supply of nuclear fuel. However, there is still room for studying flexible electrode materials in this field. Herein, we construct amidoxime group modified porous aromatic frameworks (PAF-144-AO) on flexible carbon cloths in situ using an easy to scale-up electropolymerization method followed by postdecoration to fabricate the self-standing, binder-free, metal-free electrodes (PAF-E). Based on the architectural design, adsorption sites (amidoxime groups) and catalytic sites (carbazole groups) are integrated into PAF-144-AO. Under the action of an alternating electric field, uranyl ions are selectively captured by PAN-E and subsequently transformed into Na2O(UO3·H2O)x precipitates in the presence of Na+ via reversible electron transfer, with an extraction capacity of 12.6 mg g-1 over 24 days from natural seawater. This adsorption-electrocatalysis mechanism is also demonstrated at the molecular level by ex situ spectroscopy. Our work offers an effective approach to designing flexible porous organic polymer electrodes, which hold great potential in the field of electrochemical uranium extraction from seawater.

Self-standing high-performance Si nanoparticle anchored porous carbon fiber composites for Li-ion batteries

Silicon (Si) is a highly promising anode candidate for lithium-ion batteries. However, the huge volume change of Si during the lithiation/delithiation process might cause serious structural damage, thereby restricting its potential application. Herein, a novel self-standing electrode consisting of porous carbon coated Si (Si@p-C) nanoparticles and carbon fibers (Si@p-C/p-CF) is prepared by a facile electrospinning technique. The three-dimensional carbon fiber framework derived from polyacrylonitrile serves as the support for self-standing electrode, which exhibits superior flexibility and satisfactory electrolyte penetration ability. The porous carbon matrix on the surface of Si nanoparticles can effectively buffer the volume expansion of Si during cycling and prevent direct contact between Si and the electrolyte. Attributed to these merits, the obtained (Si@p-C)0.5/p-CF electrode exhibits outstanding cycling stability with a specific capacity of 940 mAh g−1 at 0.2 A g−1 after 400 cycles, delivering great application potential.

Laser Synthesis of PtMo Single-Atom Alloy Electrode for Ultralow Voltage Hydrogen Generation.

Maximizing atom-utilization efficiency and high current stability are crucial for the platinum (Pt)-based electrocatalysts for hydrogen evolution reaction (HER). Herein, the Pt single-atom anchored molybdenum (Mo) foil (Pt-SA/Mo-L) as a single-atom alloy electrode is synthesized by the laser ablation strategy. The local thermal effect with fast rising-cooling rate of laser can achieve the single-atom distribution of the precious metals (e.g., Pt, Rh, Ir, and Ru) onto the Mo foil. The synthesized self-standing Pt-SA/Mo-L electrode exhibits splendid catalytic activity (31mV at 10mA cm-2 ) and high-current-density stability (≈850mA cm-2 for 50 h) for HER in acidic media. The strong coordination of Pt-Mo bonding in Pt-SA/Mo-L is critical for the efficient and stable HER. In addition, the ultralow electrolytic voltage of 0.598V to afford the current density of 50mA cm-2 is realized by utilization of the anodic molybdenum oxidation instead of the oxygen evolution reaction (OER). Here a universal synthetic strategy of single-atom alloys (PtMo, RhMo, IrMo, and RuMo) as self-standing electrodes is provided for ultralow voltage and membrane-free hydrogen production.

High-Yield Synthesis of Colloidal Carbon Rings and Their Applications in Self-Standing Electrodes of Li-O2 Batteries.

The use of carbon materials in porous electrodes has impressive advantages. However, precisely tailoring the multilevel pore structure of carbon electrodes remains an unsolved challenge. Here, we report a highly efficient site-selective growth strategy to synthesize colloidal carbon rings by templating patchy droplets. Carbon rings are used for the direct fabrication of self-standing porous electrodes with hierarchical pores for lithium-oxygen batteries (LOBs). In situ atomic force microscopy reveals that during discharge the discharge products densely nucleate and grow on carbon rings, demonstrating that such rings are a very potential electrode material in LOBs. The hollow carbon ring electrode (HCRE) possesses micrometer-scale channels formed by random packing of rings and nanochannels consisting of ring-shaped hollow cavities connected by nanosized pores in the wall. Both channels contribute to ion transportation and gas diffusion, but the storage of the discharge products mainly lies in micrometer-scale channels, leading to a high discharge capacity of LOBs (20 658 mAh/g). Our work paves a new way to construct hierarchically porous electrodes for application in electrocatalysis and electrochemical energy storage.

Defects-rich TiO2(B) in-situ grown on carbon fiber cloth as self-standing electrode for high-loading lithium–sulfur batteries

Poor conductivity, severe shuttling of soluble lithium polysulfides (LiPSs), and sluggish sulfur redox kinetics are inherent issues existing in lithium-sulfur batteries (LSBs). Herein, a self-standing electrode was designed and constructed via the in-situ growth of defects-rich TiO2(B) on a carbon cloth (CC) (denoted as TiO2-x(B)@CC). The strong polarity and high electrochemical activity of TiO2-x(B) enables strong chemical adsorption for LiPSs and catalyzes sulfur conversion reactions. CC as growth substrate inhibits the agglomeration of TiO2-x(B) nanosheets and improves electrical conductivity, as well as holds high sulfur loadings. Benefiting from these synergistic effects, TiO2-x(B)@CC-based cathode with a sulfur loading of ∼ 2.5 mgS cm−2 maintained a high specific capacity of 500 mAh/g over 200cycles at 2.0C. Even under high sulfur loading of ∼ 8.1 mgS cm−2 and a low electrolyte/sulfur (E/S) ratio of ∼ 6.5 μL mgS-1, it still achieved good rate capacities.

Unraveling the Cooperative Activity of Hydrophilicity, Conductivity, and Interfacial Active Sites in Alginate‐CNT‐Cuo Self‐Standing Electrodes with Benchmark‐Close Activity for Alkaline Water Splitting

AbstractDesigning electrocatalysts that excel in hydrogen and oxygen electrochemistry is crucial for sustainable hydrogen generation through electrochemical water splitting. This study presents a novel tricomponent catalyst composed of an alginate hydrogel (AL) infused with single‐walled carbon nanotubes (CNTs) and copper oxide (CuO) nanoparticles. The catalyst exhibits benchmark‐close bifunctional activity toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions. The aerophobic nature of the AL‐gel facilitates superior bubble release from the electrode, while the inclusion of CNTs mitigates charge transfer resistance. Moreover, heterojunctions of CuO and CNTs create unique interfacial active sites, culminating in high electrocatalytic water‐splitting activity. The structural rigidity of the composite permits its use as self‐standing electrodes (SSE) without using substrates or binders, enabling a direct evaluation of its activity. The composite electrode demonstrates exceptional electrocatalytic HER activity in an alkaline solution, with onset potentials of 93 mV and moderate OER activity with an onset of 155 mV. Moreover, a water electrolysis cell featuring the bifunctional SSE exhibits an open circuit voltage of 1.85 V at 100 mA.cm−2, and only 8% efficiency loss after 100 h marking this a significant stride in developing self‐standing nonprecious electrocatalysts with impressive catalytic performance.

In-situ engineering of 3D porous Co nanoparticles incorporated in B/N Co-doped carbon nanotube/nanofiber networks as integrated cathode materials for Zn-air batteries

Rational design and construction of low-cost and highly efficient bifunctional catalysts toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the commercialization of the rechargeable Zn-air batteries (ZABs). Herein, a 3D self-standing bifunctional catalytic electrode has been successfully achieved by in-situ confinement of Co nanoparticles into B/N co-doped carbon nanotube/nanofiber well-integrated networks (Co-B/N-CNTs@CFs). The purpose of designing such a 3D network structure is to optimize the electronic structure of the active sites for high electrocatalytic activity, ensure continuous and fast electron and charge transfer for high utilization of active sites, and avoid the abscission and aggregation of nanocatalysts for high electrocatalytic stability, which is confirmed by a series of experimental, characterization, and theoretical studies. As a result, the Co-B/N-CNTs@CFs as integrated cathode materials deliver efficient and stable OER/ORR performance with a ΔE of 0.59 V, largely outperforming the benchmark Pt/C-RuO2 electrode (0.71 V), and hence leading to appealing applications in both the assembled aqueous and flexible solid-state ZABs. This study forges a new path for the production of integrated cathode while enhancing their superiority, allowing for the construction of energy storage devices.

Dynamically Adaptive Bubbling for Upgrading Oxygen Evolution Reaction Using Lamellar Fern-Like Alloy Aerogel Self-Standing Electrodes.

Adopting renewable electricity to produce "green" hydrogen has been a critical challenge because at a high current density the mass transfer capability of most catalytic electrodes deteriorates significantly. Herein, a unique lamellar fern-like alloy aerogel (LFA) electrode, showing a unique dynamically adaptive bubbling capability and can effectively avoid stress concentration caused by bubble aggregation is reported. The LFA electrode is intrinsically highly catalytic-active and shows a highly porous, resilient, hierarchically ordered, and well-percolated conductive network. It not only shows superior gas evacuation capability but also exhibits significantly improved stability at high current densities, showing the record lowest oxygen evolution reaction (OER) overpotential of 244mV at 1000mA cm-2 and stably over 6000 h. With the merits of mechanical robustness, excellent electron transport, and efficient bubble evacuation, LFA can be self-standing catalytic electrode andgas diffusion layers in anion-exchange-membrane water electrolysis (AEMWE), which can achieve 3000 mA cm-2 at a low voltage of 1.88V and can sustain stable electrolysis at 2000 mA cm-2 for over 1300 h. This strategy can be extended to various gas evolution reactions as a general design rule for multiphase catalysis applications.

1D/2D heterostructure induced built-in electric field accelerate the reaction kinetics of MnO2/MXene paper-like film for advanced flexible zinc-ion batteries

Paper-like flexible electrode plays a critical importance role in booming the development of flexible energy storage devices. One-dimensional manganese dioxide (1D MnO2) shows immense advantage in flexible zinc-ion batteries (FZIBs) on account of renowned tunnel crystal structure and high operating voltage. However, inherent inferior electrical conductivity and sluggish reaction kinetics seriously hinder the practical application of FZIBs, resulting in unsatisfactory rate capability and cycle performance. Herein, 1D/2D MnO2/MXene-5 heterostructure materials were constructed by electrostatic self-assembly, which were then prepared into paper-like membrane with high energy storage active substance ratio (95.2 %) towards high capacity and ultrastable FZIBs. The built-in electric field induced by the heterostructure accelerates the electron transfer, reduces the charge transfer resistance and promotes ion diffusion, enabling the 1D/2D phase collaboration to improve the zinc ion storage of the paper-like electrode. The design achieves a high total specific capacity (based on the total cathode mass) of 314.7 mAh g−1 at 0.1 A g−1 and ultrastable of 8000 cycles at 5 A g−1 with a retention of 81.1 %. Remarkably, quasi-solid-state FZIBs with MnO2/MXene-5 membrane can deliver an outstanding reversible capacity of 273.5 mAh g−1 at 0.1 A g−1 and maintain 500 cycles at 1 A g−1 across various bending angles without decay, demonstrating excellent stability. This work provides a novel approach for the targeted design of self-standing flexible electrodes.

Self-Standing Porous Carbon Electrodes with Lean Electrolyte and High Areal Capacity Conditions for Rechargeable Lithium–Oxygen Batteries

Rechargeable lithium–oxygen batteries (LOBs) have the highest theoretical energy densities of all the lithium-based batteries; however, the key challenges facing them are excessing electrolyte amounts and operating at low areal capacity conditions. Thus far, few studies have investigated the performance of the LOBs under practical conditions using appropriate technological parameters. In this study, we prepared a series of carbon-black based self-standing membranes with different pore structures. The self-standing carbon membranes, which were prepared by applying a non-solvent-induced phase separation (NIPS) technique have investigated the relationship between the physicochemical properties and battery performance at low electrolyte/areal capacity ratio (E/C < 10 g/Ah) condition. As a result, the discharge capacity exhibits a clear correlation with the physicochemical property. On the other hand, the cycle number of the LOBs did not simply correlate with the total discharge capacity of the self-standing carbon electrodes. Interestingly, it is observed that the self-standing electrode mainly composed of a unique mesoporous structure exhibits superior cycle performance under small E/C conditions (E/C < 5 g/Ah). Therefore, a turbostratic morphology with a three-dimensional hexagonal array of the unique mesoporous structure is beneficial for exhibiting superior LOB performance under lean electrolyte condition (Figure 1). We believe that the results obtained in the present study give an insight into the development of a new direction for the material design of porous carbon electrodes for achieving a high LOB performance and long cycle life of practical significance. Figure 1

Electrochemical Performances of Powder-Impregnated Carbon Fiber-Based Positive Structural Electrodes

Carbon fibers have been in focus within the last decades in designing and constructing lightweight structures. They can be used in a large range of applications such as clothing, transportation gadget, sports materials, as well as in more unusual applications such as batteries. Their mechanical functionality in addition to good electrochemical and electrical features suggest that they can replace battery components such as the graphite anode and the current collector foils. A battery fully based on carbon fibers, often referred to as the structural battery introduced in 2004 by Wetzel et.al. [1], is a multifunctional battery that can carry the load and store the energy simultaneously. An advantage of this battery design is the less overall weight of the device due to eliminating dead mass by removing current collectors and additives from the total structure. Instead, introducing carbon fibers into lithium-ion batteries decreases the non-active mass as well as provides mechanical stability to the system. Carbon fibers show similar electrochemical behavior to graphite, and can therefore be used as negative active material thanks to their capability of reversible lithium intake capacity up to 350 mAh g-1. Furthermore, the fibers have an electrical conductivity of about 1000 S cm-1 and are therefore very suitableas current collectors [2]. Ultimately in structural batteries, also called laminated composite batteries, the carbon fiber-containing electrodes are separated by a structural battery electrolyte (SBE) consisting of a bulk phase (polymer/matrix) that encases the reinforcing between the laminas. The polymer matrix holds the carbon fibers together and transfers the loads to fibers, while carbon fibers carry the load. Figure 1a shows a cross-sectional schematic illustration of a structural battery. The lower lamina corresponds to the negative electrode where the SBE is reinforced with carbon fibers. In the upper lamina, SBE is reinforced with carbon fibers that are coated with a positive electrode material (e.g. LiFePO4 /LFP). A structural battery electrolyte (SBE) has been developed at KTH as a load-carrying polymer matrix that simultaneously conducts ions [3] and that can be combined with the carbon fiber negative electrode material. However, manufacturing the positive structural electrodes is a challenge, as the continuous carbon fibers need to be in close proximity with active materials that should also adhere well to the carbon fibers. In this context, achieving an even distribution of the positive electrode particles is expected to affect many of the structural battery performance metrics, and in particular the electrical, electrochemical and mechanical functionality [2].In this work, we produced positive structural electrodes based on PAN-based carbon fibers with powder impregnation technique in a water-based slurry composition. This technique is not only environmentally friendly but also allows good control of impregnation uniformity and active material/fiber ratio. By this method, continuous carbon fibers were impregnated (i.e., tightly mixed) with active material (LiFePO4) along with electrode components to obtain self-standing positive electrodes. The as-prepared samples show a good and uniform mixing with the active material through interlayers of carbon fibers in tow, leading to a lower internal resistance (SEM images in Figure1c.). The carbon fiber-based positive electrodes have been tested with different electrochemical methods to obtain their performances in half-cells (Figure1b.). The results show promising capacity retention and rate capability.

Pristine SWCNT Based Cathode Materials for Solid-State Li-Sulfur Batteries

Lithium-Sulfur is a long-studied, but yet to be practically implemented battery chemistry which carries a promise of creating high energy density batteries. It uses cheap and abundant materials, but faces major technological challenges. One of the key challenges is that sulfur as the cathode material has negligible electronic conductivity (5x10-28 S/m), preventing electron exchange in the cathode during battery charge/discharge cycling. The other challenge is the significant (up to 80%) volume changes of sulfur during battery cycling that leads to cracking, delamination, voids formation and loss of electrical contacts, therefore limiting battery durability. To overcome these problems, we have developed a solution-free technology of manufacturing composite self-standing electrodes by in-situ mixing of the aerosolized phases and co-deposition [1]. The electrodes consist of sulfur and catholyte particles imbedded in a 3D network of as grown, pristine single-walled carbon nanotubes. The electrodes are flexible and do not include current collector metal foils or binders. They can be produced up to 1 mm thick, up to 200 mgsulfur/cm2 loading, or 330 mAh/cm2 capacity without the loss of the SWCNT network 3D structure. The macroscopic electrical conductivity of the material increases 30 orders of magnitude compared to that of sulfur, and reaches 102-104 S/m, depending on the SWCNT concentration. The presence of SWCNT network not only solves the electrical conductivity challenge but also durability issue, since flexible/stretchable SWCNT network accommodates the volume change of the sulfur active particles without disruption of the cathode integrity. The electrodes fabricated by this method are being studied as perspective cathodes for solid-state LiS batteries. A. Kuznetsov, S. Mohanty, E. Pigos, G. Chen, W. Cai, A.R. Harutyunyan, High energy density flexible and ecofriendly lithium-ion smart battery. Energy Storage Materials, 2023 (54) 266-275, ISSN 2405-8297, doi.org/10.1016/j.ensm.2022.10.023

Amorphous high-entropy phosphoxides for efficient overall alkaline water/seawater splitting

Designing and synthesizing cost-effective bifunctional catalysts for overall alkaline water/seawater splitting is still a huge challenge for hydrogen production. Herein, Co/Ni/Fe/Mn based-amorphous high-entropy phosphoxide self-standing electrode (CNFMPO) is synthesized by the facile and fast electrodeposition method. CNFMPO exhibits excellent bifunctional electrocatalytic performances on alkaline water/seawater electrolysis. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of CNFMPO in alkaline water/seawater are as low as 43/73 and 252/282 mV to reach a current density of 10 mA cm−2, respectively. Additionally, two-electrode electrolyzers with CNFMPO||CNFMPO successfully achieve the current density of 10 mA cm−2 at low voltages of 1.54 and 1.56 V for overall alkaline water/seawater splitting, respectively. CNFMPO exhibits satisfactory long-term stability on overall alkaline water/seawater splitting for the surface reconstruction into active metal hydroxide/(oxy)hydroxide, phosphite, and phosphate. Moreover, no hypochlorite is detected during seawater electrolysis for the beneficial chlorite oxidation inhibition of the reconstructed phosphite and phosphate. The excellent catalytic performances of CNFMPO are due to the unique amorphous structure, multi-component synergistic effect, beneficial electronic structure modulation, and surface reconstruction during the catalytic reaction process. Therefore, CNFMPO has shown potential promotion to the development of the water/seawater splitting industry as a promising substituent for noble-metal electrocatalysts. This work provides new insights into the design of efficient bifunctional catalysts for overall water/seawater splitting.

Organic-inorganic hybrid crystal-assisted etching of nickel foam for the collectively exhaustive electrochemical performance of oxygen evolution reaction.

An organic-inorganic hybrid crystal, violet-crystal (VC), was used to etch the nickel foam (NF) to fabricate a self-standing electrode for the water oxidation reaction. The efficacy of VC-assisted etching manifests the promising electrochemical performance towards the oxygen evolution reaction (OER), requiring only ~356 and ~376 mV overpotentials to reach 50 and 100 mA cm-2, respectively. The OER activity improvement is attributed to the collectively exhaustive effects arising from the incorporation of various elements in the NF, and the enhancement of active site density. Furthermore, the self-standing electrode is robust, exhibiting a stable OER activity after 4,000 cyclic voltammetry cycles, and ~ 50 h. The anodic transfer coefficients (aa) show that the first electron transfer step is the rate-determining step on the surface of NF-VCs-1.0 (NF etched by 1 g of VCs) electrode, while the chemical step involving dissociation following the first electron transfer step is identified as the rate-limiting step in other electrodes. The lowest Tafel slope value observed in the NF-VCs-1.0 electrode indicates the high surface coverage of oxygen intermediates and more favorable OER reaction kinetics, as confirmed by high interfacial chemical capacitance and low charge transport/interfacial resistance.