2D Tungsten Borides Induced Interfacial Modulation Engineering Toward High-Rate Performance Zinc-Iodine Battery.

Aqueous zinc-iodine batteries are promising candidates for large-scale energy storage due to their high energy density and low cost. However, their development is hindered by several drawbacks, including zinc dendrites, anode corrosion, and the shuttle of polyiodides. Here, the design of 2D-shaped tungsten boride nanosheets with abundant borophene subunits-based active sites is reported to guide the (002) plane-dominated deposition of zinc while suppressing side reactions, which facilitates interfacial nucleation and uniform growth of zinc. Meanwhile, the interfacial d-band orbits of tungsten sites can further enhance the anchoring of polyiodides on the surface, to promote the electrocatalytic redox conversion of iodine. The resulting tungsten boride-based I2 cathodes in zinc-iodine cells exhibit impressive cyclic stability after 5000 cycles at 50 C, which accelerates the practical applications of zinc-iodine batteries.

Cascade Synthesis of Fe-N2-Fe Dual-Atom Catalysts for Superior Oxygen Catalysis.

Dual-atom catalysts (DACs) have been proposed to break the limitation of single-atom catalysts (SACs) in the synergistic activation of multiple molecules and intermediates, offering an additional degree of freedom for catalytic regulation. However, it remains a challenge to synthesize DACs with high uniformity, atomic accuracy, and satisfactory loadings. Herein, we report a facile cascade synthetic strategy for DAC via precise electrostatic interaction control and neighboring vacancy construction. We synthesized well-defined, uniformly dispersed dual Fe sites which were connected by two nitrogen bonds (denoted as Fe-N2-Fe). The as-synthesized DAC exhibited superior catalytic performances towards oxygen reduction reaction, including good half-wave potential (0.91 V), high kinetic current density (21.66 mA cm-2), and perfect durability. Theoretical calculation revealed that the DAC structure effectively tunes the oxygen adsorption configuration and decreases the cleavage barrier, thereby improving the catalytic kinetics. The DAC-based zinc-air batteries exhibited impressive power densities of 169.8 and 52.18 mW cm-2 at 25 oC and -40 oC, which is 1.7 and 2.0 times higher than those based on Pt/C+Ir/C, respectively. We also demonstrated the universality of our strategy in synthesizing other M-N2-M DACs (M= Co, Cu, Ru, Pd, Pt, and Au), facilitating the construction of a DAC library for different catalytic applications.

Insights into Electrode Architectures and Lithium-Ion Transport in Polycrystalline V2 O5 Cathodes of Solid-State Batteries.

Polymer-based solid-state batteries (SSBs) have received increasing attentions due to the absence of interfacial problems in sulfide/oxide-type SSBs, but the lower oxidation potential of polymer-based electrolytes greatly limits the application of conventional high-voltage cathode such as LiNix Coy Mnz O2 (NCM) and lithium-rich NCM. Herein, this study reports on a lithium-free V2 O5 cathode that enables the applications of polymer-based solid-state electrolyte (SSE) with high energy density due to the microstructured transport channels and suitable operational voltage. Using a synergistic combination of structural inspection and non-destructive X-ray computed tomography (X-CT), it interprets the chemo-mechanical behavior that determines the electrochemical performance of the V2 O5 cathode. Through detailed kinetic analyses such as differential capacity and galvanostatic intermittent titration technique (GITT), it is elucidated that the hierarchical V2 O5 constructed through microstructural engineering exhibits smaller electrochemical polarization and faster Li-ion diffusion rates in polymer-based SSBs than those in the liquid lithium batteries (LLBs). By the hierarchical ion transport channels created by the nanoparticles against each other, superior cycling stability (≈91.7% capacity retention after 100 cycles at 1 C) is achieved at 60 °C in polyoxyethylene (PEO)-based SSBs. The results highlight the crucial role of microstructure engineering in designing Li-free cathodes for polymer-based SSBs.

Zinc-Doping Strategy on P2-Type Mn-Based Layered Oxide Cathode for High-Performance Potassium-ion Batteries.

Mn-based layered oxide is extensively investigated as a promising cathode material for potassium-ion batteries due to its high theoretical capacity and natural abundance of manganese. However, the Jahn-Teller distortion caused by high-spin Mn3+ (t2g 3 eg 1 ) destabilizes the host structure and reduces the cycling stability. Here, K0.02 Na0.55 Mn0.70 Ni0.25 Zn0.05 O2 (denoted as KNMNO-Z) is reported to inhibit the Jahn-Teller effect and reduce the irreversible phase transition. Through the implementation of a Zn-doping strategy, higher Mn valence is achieved in the KNMNO-Z electrode, resulting in a reduction of Mn3+ amount and subsequently leading to an improvement in cyclic stability. Specifically, after 1000 cycles, a high retention rate of 97% is observed. Density functional theory calculations reveals that low-valence Zn2+ ions substituting the transition metal position of Mn regulated the electronic structure around the MnO bonding, thereby alleviating the anisotropic coupling between oxidized O2- and Mn4+ and improving the structural stability. K0.02 Na0.55 Mn0.70 Ni0.25 Zn0.05 O2 provided an initial discharge capacity of 57 mAh g-1 at 100 mA g-1 and a decay rate of only 0.003% per cycle, indicating that the Zn-doped strategy is effective for developing high-performance Mn-based layered oxide cathode materials in PIBs.

Phosphorus Regulated Cobalt Oxide@Nitrogen-Doped Carbon Nanowires for Flexible Quasi-Solid-State Supercapacitors.

Battery-type materials are promising candidates for achieving high specific capacity for supercapacitors. However, their slow reaction kinetics hinders the improvement in electrochemical performance. Herein, a hybrid structure of P-doped Co3 O4 (P-Co3 O4 ) ultrafine nanoparticles in situ encapsulated into P, N co-doped carbon (P, N-C) nanowires by a pyrolysis-oxidation-phosphorization of 1D metal-organic frameworks derived from Co-layered double hydroxide as self-template and reactant is reported. This hybrid structure prevents active material agglomeration and maintains a 1D oriented arrangement, which exhibits a large accessible surface area and hierarchically porous feature, enabling sufficient permeation and transfer of electrolyte ions. Theoretical calculations demonstrate that the P dopants in P-Co3 O4 @P, N-C could reduce the adsorption energy of OH- and regulate the electrical properties. Accordingly, the P-Co3 O4 @P, N-C delivers a high specific capacity of 669 mC cm-2 at 1 mA cm-2 and an ultralong cycle life with only 4.8% loss over 5000 cycles at 30 mA cm-2 . During the fabrication of P-Co3 O4 @P, N-C, Co@P, N-C is simultaneously developed, which can be integrated with P-Co3 O4 @P, N-C for the assembly of asymmetric supercapacitors. These devices achieve a high energy density of 47.6 W h kg-1 at 750 W kg-1 and impressive flexibility, exhibiting a great potential in practical applications.

Phosphorus-Mediated MoS2 Nanowires as a High-Performance Electrode Material for Quasi-Solid-State Sodium-Ion Intercalation Supercapacitors.

Molybdenum disulfide (MoS2 ) is a promising electrode material for electrochemical energy storage owing to its high theoretical specific capacity and fascinating 2D layered structure. However, its sluggish kinetics for ionic diffusion and charge transfer limits its practical applications. Here, a promising strategy is reported for enhancing the Na+ -ion charge storage kinetics of MoS2 for supercapacitors. In this strategy, electrical conductivity is enhanced and the diffusion barrier of Na+ ion is lowered by a facile phosphorus-doping treatment. Density functional theory results reveal that the lowest energy barrier of dilute Na-vacancy diffusion on P-doped MoS2 (0.11 eV) is considerably lower than that on pure MoS2 (0.19 eV), thereby signifying a prominent rate performance at high Na intercalation stages upon P-doping. Moreover, the Na-vacancy diffusion coefficient of the P-doped MoS2 at room temperatures can be enhanced substantially by approximately two orders of magnitude (10-6 -10-4 cm2 s-1 ) compared with pure MoS2 . Finally, the quasi-solid-state asymmetrical supercapacitor assembled with P-doped MoS2 and MnO2 , as the positive and negative electrode materials, respectively, exhibits an ultrahigh energy density of 67.4 W h kg-1 at 850 W kg-1 and excellent cycling stability with 93.4% capacitance retention after 5000 cycles at 8 A g-1 .

Efficient and stable semitransparent perovskite photovoltaics via a Lewis base incorporation.

Semitransparent perovskite solar cells (ST-PSCs) have great potential in building integrated photovoltaics. However, semitransparent devices suffer from a low electron mobility and an imbalanced charge-carrier transport, leading to an unsatisfactory power conversion efficiency (PCE) and limited stability. Herein, we report a high-performance ST-PSC via the incorporation of a special Lewis base. A better perovskite with an improved crystallinity and less defects was achieved, and a matched energy level alignment between the perovskite and [6,6]-phenyl-C61-butyric acid methyl ester was also induced, thereby leading to a high electron mobility and an exceptional balance of hole and electron mobility approaching 1 : 1. The prepared ST-PSC exhibited a PCE of 20.22% at average visible transmittance (AVT) of 4.93%, 18.32% at AVT of 14.38%, and 15.00% at AVT of 25.65%. These PCEs are the highest values among those ST-PSCs based on top metallic electrodes at a close AVT. The ST-PSCs maintained 92% of the initial PCE in storage for 1000 h, and they held 84% of the initial PCE under the continuous maximum power point tracking measurement for 530 hours. The work paves the way to realize ST-PSCs with a high PCE, high light utilization efficiency and substantially enhanced stability.

Fundamentally Manipulating the Electronic Structure of Polar Bifunctional Catalysts for Lithium-Sulfur Batteries: Heterojunction Design versus Doping Engineering.

Heterogeneous structures and doping strategies have been intensively used to manipulate the catalytic conversion of polysulfides to enhance reaction kinetics and suppress the shuttle effect in lithium-sulfur (Li-S) batteries. However, understanding how to select suitable strategies for engineering the electronic structure of polar catalysts is lacking. Here, a comparative investigation between heterogeneous structures and doping strategies is conducted to assess their impact on the modulation of the electronic structures and their effectiveness in catalyzing the conversion of polysulfides. These findings reveal that Co0.125Zn0.875Se, with metal-cation dopants, exhibits superior performance compared to CoSe2/ZnSe heterogeneous structures. The incorporation of low Co2+ dopants induces the subtle lattice strain in Co0.125Zn0.875Se, resulting in the increased exposure of active sites. As a result, Co0.125Zn0.875Se demonstrates enhanced electron accumulation on surface Se sites, improved charge carrier mobility, and optimized both p-band and d-band centers. The Li-S cells employing Co0.125Zn0.875Se catalyst demonstrate significantly improved capacity (1261.3 mAh g-1 at 0.5 C) and cycle stability (0.048% capacity delay rate within 1000 cycles at 2 C). This study provides valuable guidance for the modulation of the electronic structure of typical polar catalysts, serving as a design directive to tailor the catalytic activity of advanced Li-S catalysts.

Interfacial "Double-Terminal Binding Sites" Catalysts Synergistically Boosting the Electrocatalytic Li2S Redox for Durable Lithium-Sulfur Batteries.

Catalytic conversion of polysulfides emerges as a promising approach to improve the kinetics and mitigate polysulfide shuttling in lithium-sulfur (Li-S) batteries, especially under conditions of high sulfur loading and lean electrolyte. Herein, we present a separator architecture that incorporates double-terminal binding (DTB) sites within a nitrogen-doped carbon framework, consisting of polar Co0.85Se and Co clusters (Co/Co0.85Se@NC), to enhance the durability of Li-S batteries. The uniformly dispersed clusters of polar Co0.85Se and Co offer abundant active sites for lithium polysulfides (LiPSs), enabling efficient LiPS conversion while also serving as anchors through a combination of chemical interactions. Density functional theory calculations, along with in situ Raman and X-ray diffraction characterizations, reveal that the DTB effect strengthens the binding energy to polysulfides and lowers the energy barriers of polysulfide redox reactions. Li-S batteries utilizing the Co/Co0.85Se@NC-modified separator demonstrate exceptional cycling stability (0.042% per cycle over 1000 cycles at 2 C) and rate capability (849 mAh g-1 at 3 C), as well as deliver an impressive areal capacity of 10.0 mAh cm-2 even in challenging conditions with a high sulfur loading (10.7 mg cm-2) and lean electrolyte environments (5.8 µL mg-1). The DTB site strategy offers valuable insights into the development of high-performance Li-S batteries.

Conductive N, S doped Copolymers as Stable Metal-Free Electrocatalysts for Water Splitting.

Noble metals (Pt) and metal oxides (IrC and RuO2) are heavily utilized as benchmark electrocatalysts for alkaline water splitting; however, these materials possess several drawbacks including high cost, poor selectivity and stability, and high environmental impact. To address these issues, we synthesized a novel metal-free conducting polypyrrole-polythiophene (Ppy-Ptp) copolymer and a separate Ppy electrode material for water-splitting applications. The Ppy-Ptp and Ppy electrocatalysts exhibited remarkable activity in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. The optimal Ppy-Ptp (1:3) formulation, when deposited on a conductive nickel foam (NF) substrate, exhibited an exceptional OER performance with a low overpotential of approximately 250 mV at 20 mAcm-2, thereby outperforming the benchmark IrC/NF electrocatalyst (290 mV, 20 mAcm-2). Additionally, a similarly prepared Ppy/NF electrocatalyst exhibited an extraordinary HER performance with an overpotential of approximately 72 mV at 10 mA cm-2. Furthermore, an alkaline anion-exchange membrane (AEM) electrolyzer incorporating Ppy-Ptp (1:3) and Ppy as the anode and cathode materials, respectively, displayed operating potentials of 1.55, 1.70, and 1.78 V at 10, 50, and 100 mA cm-2, which are lower than those observed in previously reported electrolyzers. This electrolyzer also exhibited considerable operational endurance over 50 h at 50 mA cm-2, over which a negligible decay of 0.02 V was observed. The novel polymer-based metal-free catalysts presented herein therefore exhibit considerable potential as alternative electrocatalytic materials for sustainable industrial-scale H2 synthesis.

Novel method to evaluate moisture permeation of the metal barrier coating on polymer substrate.

Water is detrimental to the performance of organic light-emitting devices and organic solar cells. A novel weight gain test (WGT) was introduced and demonstrated to measure the low permeation of water vapor through a metallic barrier coating on a polymer substrate. By using the WGT, the values of solubility, diffusivity and permeability for a sample are obtained with a simple experimental setup and diffusion equation. The WGT method has potential for the measurement of water-vapor permeation properties for samples with good barrier properties and irregular shape.

Cross-Linked γ-Polyglutamic Acid as an Aqueous SiOx Anode Binder for Long-Term Lithium-Ion Batteries.

Silicon oxide (SiOx) has outstanding capacity and stable lithium-ion uptake/removal electrochemistry as a lithium-ion anode material; however, its practical massive commercialization is encumbered by unavoidable challenges, such as dynamic volume changes during cycling and inherently inferior ionic conductivities. Recent literature has offered a consensus that binders play a critical role in affecting the electrochemical performance of Si-based electrodes. Herein, we report an aqueous binder, γ-polyglutamic acid cross-linked by epichlorohydrin (PGA-ECH), that guarantees enhanced properties for SiOx anodes to implement long-term cycling stability. The abundant amide, carboxyl, and hydroxyl groups in the binder structure form strong interactions with the SiOx surface, which contribute strong interfacial adhesion. The robust covalent interactions and strong supramolecular interactions in the binder ensure mechanical strength and elasticity. Additionally, the interactions between lithium ions and oxygen (nitrogen) atoms of carboxylate (peptide) bonds, which serve as a Lewis base, facilitate the diffusion of lithium ions. A SiOx anode using this PGA-ECH binder exhibits an impressive initial discharge capacity of 1962 mA h g-1 and maintains a high capacity of 900 mA h g-1 after 500 cycles at 500 mA g-1. Meanwhile, the assembled SiOx||LiNi0.6Co0.2MnO0.2 full cell shows a reversible capacity of 155 mA g-1 and displays 73% capacity retention after 100 cycles.

High-Performance Photoelectrochemical Desalination Based on the Dye-Sensitized Bi2O3 Anode.

In this work, a solar-driven redox flow desalination system is reported, which combines a solar cell based on a Bi2O3 photoanode and a redox flow desalination cell through an integrated electrode. The Bi2O3 film was prepared through a simple one-step water bath deposition method and served as a photoanode after the coating of the N719 dye. The activated carbon (AC)-coated graphite paper served as both the integrated electrode and counter electrode. The I3-/I- redox electrolyte circulates in the solar cell channel between the photoanode and intergrated electrode, while the [Fe(CN)6]4-/[Fe(CN)6]3- electrolyte circulates in the redox flow desalination part between the integrated electrode and counter electrode. This dye-sensitized solar-driven desalination cell is capable of achieving a maximum salt removal rate of 62.89 µg/(cm2·min) without consuming any electrical power. The combination of the solar cell and redox flow desalination is highly efficient with double functions of desalination and energy release using light as a driving force. This current research work is significant for the development of efficient and stable photoanode materials in photoelectrochemical desalination.

Recent progress in metal-organic framework/graphene-derived materials for energy storage and conversion: design, preparation, and application.

Graphene or chemically modified graphene, because of its high specific surface area and abundant functional groups, provides an ideal template for the controllable growth of metal-organic framework (MOF) particles. The nanocomposite assembled from graphene and MOFs can effectively overcome the limitations of low stability and poor conductivity of MOFs, greatly widening their application in the field of electrochemistry. Furthermore, it can also be utilized as a versatile precursor due to the tunable structure and composition for various derivatives with sophisticated structures, showing their unique advantages and great potential in many applications, especially energy storage and conversion. Therefore, the related studies have been becoming a hot research topic and have achieved great progress. This review summarizes comprehensively the latest methods of synthesizing MOFs/graphene and their derivatives, and their application in energy storage and conversion with a detailed analysis of the structure-property relationship. Additionally, the current challenges and opportunities in this field will be discussed with an outlook also provided.

Aqueous Supramolecular Binder for a Lithium-Sulfur Battery with Flame-Retardant Property.

A lithium-sulfur (Li-S) battery based on multielectron chemical reactions is considered as a next-generation energy-storage device because of its ultrahigh energy density. However, practical application of a Li-S battery is limited by the large volume changes, insufficient ion conductivity, and undesired shuttle effect of its sulfur cathode. To address these issues, an aqueous supramolecular binder with multifunctions is developed by cross-linking sericin protein (SP) and phytic acid (PA). The combination of SP and PA allows one to control the volume change of the sulfur cathode, benefit soluble polysulfides absorbing, and facilitate transportation of Li+. Attributed to the above merits, a Li-S battery with the SP-PA binder exhibits a remarkable cycle performance improvement of 200% and 120% after 100 cycles at 0.2 C compared with Li-S batteries with PVDF and SP binders. In particular, the SP-PA binder in the electrode displays admirable flame-retardant performance due to formation of an isolating layer and the release of radicals.

Sub-Nanometer Pt Clusters on Defective NiFe LDH Nanosheets as Trifunctional Electrocatalysts for Water Splitting and Rechargeable Hybrid Sodium-Air Batteries.

It is challenging to develop highly efficient and stable multifunctional electrocatalysts for improving the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR) for sustainable energy conversion and storage systems such as water-alkali electrolyzers (WAEs) and hybrid sodium-air batteries (HSABs). In this work, sub-nm Pt nanoclusters (NCs) on defective NiFe layered double hydroxide nanosheets (NixFe LDHs) are synthesized by a facile electrodeposition method. Due to the synergistic effect between Pt NCs and abundant atomic M(II) defects, along with hierarchical porous nanostructures, the Pt/NixFe LDHs catalysts exhibit superior trifunctional electrocatalytic activity and durability toward the HER/OER/ORR. A WAE fabricated with Pt/NixFe LDHs electrodes needs 1.47 V to reach a current density of 10 mA cm-2, much lower than that of the mixed 20% Pt/C and 20% Ir/C catalysts. An HSAB assembled by Pt/NixFe LDHs as a binder-free air cathode displays a high open-circuit voltage, a narrow overpotential gap, and remarkable rechargeability. This work provides a feasible strategy for constructing freestanding efficient trifunctional electrocatalysts for sustainable energy conversion and storage systems.

Electrocatalytic desalination with CO2 reduction and O2 evolution.

Multifunctional electrocatalytic desalination is a promising method to increase the production of additional valuable chemicals during the desalination process. In this work, a multifunctional desalination device was demonstrated to effectively desalinate brackish water (15 000 ppm) to 9 ppm while generating formate from captured CO2 at the Bi nanoparticle cathode and releasing oxygen at the Ir/C anode. The salt feed channel is sandwiched between two electrode chambers and separated by ion-exchange membranes. The electrocatalytic process accelerates the transportation of sodium ions and chloride ions in the brine to the cathode and anode chamber, respectively. The fastest salt removal rate to date was obtained, reaching up to 228.41 µg cm-2 min-1 with a removal efficiency of 99.94%. The influences of applied potential and the concentrations of salt feed and electrolyte were investigated in detail. The current research provides a new route towards an electrochemical desalination system.

High-Efficiency Flexible Organic Photovoltaics and Thermoelectricities Based on Thionyl Chloride Treated PEDOT:PSS Electrodes.

Conducting polymers have received tremendous attentions owing to their great potentials to harvest both luminous and thermal energies. Here, we reported a flexible transparent electrode of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with highly electrical conductivity and raised Seebeck coefficient via thionyl chloride treatments. The comprehensive studies of optical, electrical, morphological, structural, and thermoelectrical properties, work function, and stability of the PEDOT:PSS transparent electrodes were systematically evaluated and described. On the basis of the PEDOT:PSS transparent electrodes, the resultant flexible organic solar cells yielded a high power conversion efficiency of 15.12%; meanwhile, the flexible thermoelectricities exhibited the raised power factor of 115.9 µW m-1 K-2, which outperformed the four kinds of rigid thermoelectricities with conventional acid and base treatments.

Stable and recyclable Fe3C@CN catalyst supported on carbon felt for efficient activation of peroxymonosulfate.

Stable and recyclable catalysts are crucial to the peroxymonosulfate (PMS) based advanced oxidation process (AOPs) for wastewater treatment. Herein, nitrogen-rich carbon wrapped Fe3C (Fe3C@CN) on carbon felt (CF) substrate was synthesized by using Prussian blue (PB) loaded CF as the precursors. The obtained Fe3C@CN/CF catalyst was applied for degradation of bisphenol A (BPA) via the heterogeneous catalytic activation of PMS. Results showed that ~91.7%, 95.2%, 98.1% and 99.1% of BPA (20 mg/L) were eliminated in the Fe3C@CN/CF + PMS system within 4, 10, 20 and 30 min, respectively. The fast degradation kinetics is attributed to the production of abundant reactive species (OH, SO4- and 1O2) in the Fe3C@CN/CF + PMS system, as demonstrated by the electron paramagnetic resonance spectroscopy and quench experiments. The Fe3C@CN/CF catalyst was stable and can be easily recycled by using an external magnet. The results indicated that the nanoconfined Fe3C endowed Fe3C@CN/CF with high stability and magnetic property and enabled the efficient electron transfer for PMS activation. This study provides a cost-effective approach for the fabrication of stable and recyclable Fe3C@CN/CF catalyst, and shed a new light on the rational design of multifunctional catalyst for advanced water remediation.