Transference Number Research Articles

Designing Multi-functional Separators With Regulated Ion Flux and Selectivity for Macrobian Zinc Ion Batteries.

The success of achieving scale-up deployment of zinc ion batteries is to selectively regulate the rapid and dendrite-free growth of zinc anodes. Herein, this is proposed that a creative design strategy of constructing multi-functional separators (MFS) to stabilize the zinc anodes. By in situ decorating metal-organic-framework coating on commercial glass fiber, the upgraded separator is of remarkable benefit for strong anion (SO4 2-) anchoring, uniform ion flux across the interface, and boosted Zn2+ desolvation. Such a feature selectively promotes the Zn2+ transportation efficiency, which enables a high Zn2+ transference number of 0.81, enhanced ionic conductivity, and a superb exchange current density of 12.80 mA cm-2. Consequently, the zinc anode can be operated stably with an ultra-long service lifetime of over 4800 h in symmetric cells and improved cycling endurance in full batteries. This work paves an attractive pathway to design multi-functional separators with regulated ion flux and selectivity toward high-energy metal batteries beyond zinc chemistry.

Abnormal Freezing Effect on Electron Conduction of Ball-milled Lanthanum Trihydride for Superionic Conductor.

A recent finding shows that lattice deformation could transform the mixed electronic/hydride (H-) conducting lanthanum trihydride (LaH3) to a superionic H- conductor. Such a feature would enable the development of a brand-new all-solid-state hydride ion battery. It is essential to elucidate the mechanism of such a phenomenon. Here, we disclose an abnormal freezing effect on the electronic conductivity (σe) of the ball-milled LaH3; that is, σe can be lowered by over 2 orders of magnitude upon a low-temperature treatment. Low-temperature Raman reveals that at low temperatures, lattice deformation has a noticeable influence on the interaction of hydrogen at octahedral (Ho) and tetrahedral (Ht) sites, which may play a crucial role in hindering electron conduction. This freezing effect can significantly improve the ionic transfer number of rare earth-based H- conductors and provide a new direction to the development of solid electrolytes for low-temperature all-solid-state batteries.

Major facilitator family transporters specifically enhance caffeyl alcohol uptake during C-lignin biosynthesis.

The mode of transport of lignin monomers to the sites of polymerization in the apoplast remains controversial. C-Lignin is a recently discovered form of lignin found in some seed coats that is composed exclusively of units derived from caffeyl alcohol. RNA-seq and proteome analyses identified a number of transporters co-expressed with C-lignin deposition in the seed coat of Cleome hassleriana. Cloning and influx/efflux analysis assays in yeast identified two low-affinity transporters, ChPLT3 and ChSUC1, that were active with caffeyl alcohol but not with the classical monolignols p-coumaryl, coniferyl, and sinapyl alcohols, consistent with molecular modeling and docking studies. Expression of ChPLT3 in Arabidopsis seedlings enhanced root growth in the presence of caffeyl alcohol, and expression of ChPLT3 and ChSUC1 correlated with lignin C-unit content in hairy roots of Medicago truncatula. We present a model, consistent with phylogenetic and evolutionary considerations, whereby passive caffeyl alcohol transport may be supplemented by hitchhiking on secondary active transporters to ensure the synthesis of C-lignin, and inhibition of synthesis of G-lignin, in the apoplast.

Host-Guest Interactions of Metal-Organic Framework Enable Highly Conductive Quasi-Solid-State Electrolytes for Li-CO2 Batteries.

High-energy lithium (Li)-based batteries, especially rechargeable Li-CO2 batteries with CO2 fixation capability and high energy density, are desirable for electrified transportation and other applications. However, the challenges of poor stability, low energy efficiency, and leakage of liquid electrolytes hinder the development of Li-CO2 batteries. Herein, a highly conductive and stable metal-organic framework-encapsulated ionic liquid (IL@MOF) electrolyte system is developed for quasi-solid-state Li-CO2 batteries. Benefiting from the host-guest interaction of MOFs with open micromesopores and internal IL, the optimized IL@MOF electrolytes exhibit a high ionic conductivity of 1.03 mS cm-1 and a high transference number of 0.80 at room temperature. The IL@MOF electrolytes also feature a wide electrochemical stability window (4.71 V versus Li+/Li) and a wide working temperature (-60 °C ∼ 150 °C). The IL@MOF electrolytes also enable Li+ and electrons transport in the carbon nanotubes-IL@MOF (CNT-IL@MOF) solid cathodes in quasi-solid-state Li-CO2 batteries, delivering a high specific capacity of 13,978 mAh g-1 (50 mA g-1), a long cycle life of 441 cycles (500 mA g-1 and 1000 mAh g-1), and a wide operation temperature of -60 to 150 °C. The proposed MOF-encapsulated IL electrolyte system presents a powerful strategy for developing high-energy and highly safe quasi-solid-state batteries.

Long-Range Surface Forces in Salt-in-Ionic Liquids.

Ionic liquids (ILs) are a promising class of electrolytes with a unique combination of properties, such as extremely low vapor pressures and nonflammability. Doping ILs with alkali metal salts creates an electrolyte that is of interest for battery technology. These salt-in-ionic liquids (SiILs) are a class of superconcentrated, strongly correlated, and asymmetric electrolytes. Notably, the transference numbers of the alkali metal cations have been found to be negative. Here, we investigate Na-based SiILs with a surface force apparatus, X-ray scattering, and atomic force microscopy. We find evidence of confinement-induced structural changes, giving rise to long-range interactions. Force curves also reveal an electrolyte structure consistent with our predictions from theory and simulations. The long-range steric interactions in SiILs reflect the high aspect ratio of compressible aggregates at the interfaces rather than the purely electrostatic origin predicted by the classical electrolyte theory. This conclusion is supported by the reported anomalous negative transference numbers, which can be explained within the same aggregation framework. The interfacial nanostructure should impact the formation of the solid electrolyte interphase in SiILs.

Cellulose Derivative and Polyionic Liquid Crosslinked Network Gel Electrolytes for Sodium Metal Quasi‐Solid‐State Batteries

AbstractSodium metal batteries have gained attention as a potential solution to the low energy densities presented by current sodium‐ion batteries. However, the commonly available electrolyte systems usually fall short in safety performance. Gel polymer electrolytes, closely resembling liquid electrolytes, offer a promising balance of performance and developmental potential. A proposed polymer plastic‐crystal ionic gel composite electrolyte, featuring a polycation auxiliary chain, innovatively copolymerizes ionic liquid cations with electrolyte additives. These auxiliary chains crosslink with the main chain, attracting anions from the ionic liquid and sodium salts. Both experimental evidence and theoretical calculations affirm that this electrolyte exhibits high cation transference numbers and significant mean square displacement radii. By facilitating uniform sodium ion migration, the electrolyte has powered sodium symmetrical cells for over 550 h and has supported stable cycling of Na3V2(PO4)3 (NVP)‐sodium metal batteries at a 1 C rate for more than 800 cycles. These achievements underscore its potential in advancing the development of condensed‐state sodium metal batteries.

Polymerizable Ionic Liquid-Based Gel Polymer Electrolytes Enabled by High-Energy Electron Beam for High-Performance Lithium-Ion Batteries.

Polymerizable ionic liquid-based gel polymer electrolytes (PIL-GPEs) were developed for the first time using high-energy electron beam irradiation for high-performance lithium-ion batteries (LIBs). By incorporating an imidazolium-based ionic liquid (PIL) into the polymer network, PIL-GPEs achieved high ionic conductivity (1.90 mS cm-1 at 25 °C), a lithium transference number of 0.62, and an electrochemical stability exceeding 5 V. E-beam irradiation enabled rapid polymer network formation within a metal-cased battery structure, eliminating the need for initiators and improving the process efficiency. In the NCM811/PIL-GPE/Li cells, PIL-GPE (8:2) delivered an initial discharge capacity of 198.8 mAh g-1 with 82% retention at 100 cycles, demonstrating enhanced thermal stability and cycling performance compared to traditional GPEs. The demonstrated PIL-GPEs demonstrate strong potential for high-stability, high-performance LIB applications.

Coordination‐Driven Crosslinking Electrolytes for Fast Lithium‐Ion Conduction and Solid‐State Battery Applications

AbstractRechargeable batteries paired with lithium (Li) metal anodes are considered to be promising high‐energy storage systems. However, the use of highly reactive Li metal and the formation of Li dendrites during battery operation would cause safety concerns, especially with the employment of highly flammable liquid electrolytes. Herein, a general strategy by engineering coordination‐driven crosslinking networks is proposed to achieve high‐performance solid polymer electrolytes. Through the coordination of metal‐organic polyhedra (MOPs) with cellulose‐based copolymers, the Li+‐conducted hypercrosslinked MOP (CHMOP‐Li) polymer network is capable of enabling the rapid transport of Li+. In addition to the high Li+ conductivity (1.02×10−3 S cm−1 at 25 °C), CHMOP‐Li electrolyte also exhibits a high Li+ transference number (0.75) and a wide electrochemical stability window. Benefiting from the thermally stable and mechanically strong CHMOP‐Li electrolyte film, the short‐circuiting of the symmetric batteries is prevented even after 3200 h of cycling and a high specific energy of 300 Wh kg−1 is achieved for the Li‐metal battery. The solid‐state Li−O2 batteries fabricated with CHMOP‐Li electrolyte also show good cycling performance (500 cycles) and high discharge capacity (15740 mAh g−1). The proposed coordination‐driven crosslinking strategies offer an alternative route to design high‐performance next‐generation sustainable battery chemistries.

Coordination-Driven Crosslinking Electrolytes for Fast Lithium-Ion Conduction and Solid-State Battery Applications.

Rechargeable batteries paired with lithium (Li) metal anodes are considered to be promising high-energy storage systems. However, the use of highly reactive Li metal and the formation of Li dendrites during battery operation would cause safety concerns, especially with the employment of highly flammable liquid electrolytes. Herein, a general strategy by engineering coordination-driven crosslinking networks is proposed to achieve high-performance solid polymer electrolytes. Through the coordination of metal-organic polyhedra (MOPs) with cellulose-based copolymers, the Li+-conducted hypercrosslinked MOP (CHMOP-Li) polymer network is capable of enabling the rapid transport of Li+. In addition to the high Li+ conductivity (1.02×10-3 S cm-1 at 25 °C), CHMOP-Li electrolyte also exhibits a high Li+ transference number (0.75) and a wide electrochemical stability window. Benefiting from the thermally stable and mechanically strong CHMOP-Li electrolyte film, the short-circuiting of the symmetric batteries is prevented even after 3200 h of cycling and a high specific energy of 300 Wh kg-1 is achieved for the Li-metal battery. The solid-state Li-O2 batteries fabricated with CHMOP-Li electrolyte also show good cycling performance (500 cycles) and high discharge capacity (15740 mAh g-1). The proposed coordination-driven crosslinking strategies offer an alternative route to design high-performance next-generation sustainable battery chemistries.

Realization of Hydrogel Electrolytes with High Thermoelectric Properties: Utilization of the Hofmeister Effect.

Ionic thermoelectric materials, renowned for their high Seebeck coefficients, are gaining prominence for their potential in harvesting low-grade waste heat. However, the theoretical underpinnings for enhancing the performance of these materials remain underexplored. In this study, the Hoffmeister effect was leveraged to augment the thermoelectric properties of hydrogel-based ionic thermoelectric materials. A series of PAAm-x Zn(CF3SO3)2, PAAm-x ZnSO4, and PAAm-x Zn(ClO4)2 hydrogels were synthesized, using polyacrylamide (PAAm) as the matrix and three distinct zinc salts with varying anion volumes to impart the Hoffmeister effect. Exceptionally, the most cost-effective ZnSO4 yielded the highest ionic Seebeck coefficient among the hydrogels, with PAAm-1 ZnSO4 achieving a remarkable value of -3.72 mV K-1. To elucidate the underlying mechanism, we conducted an innovative analysis correlating the Seebeck coefficient with the zinc ion transfer number. Additionally, the hydrogel materials demonstrated outstanding mechanical properties, including high elongation at break (>1400% at its peak), exceptional resilience (virtually no hysteresis loops), and robust fatigue resistance (overlapping cyclic tensile curves). This work not only advances the understanding of ionic thermoelectric materials but also showcases the potential of hydrogels for practical waste heat recovery applications.

Solvate Complex LiAlCl4·SO2: Synthesis and Physical-Chemical Properties.

This work describes the synthesis of the LiAlCl4·SO2 solvate complex and its properties. Its composition was determined using thermogravimetric analysis, Raman spectroscopy, and UV-vis spectroscopy. The specific ionic conductivity of LiAlCl4·SO2 is 4.7 × 10-2 S·cm-1. The dynamic viscosity is 19 cP at 25 °C, and the lithium transference number is 0.78. The melting point (+2.5 °C) and decomposition temperature (+60 °C) of LiAlCl4·SO2 were determined by simultaneous thermogravimetric analysis and differential scanning calorimetry. The structure of the solvate complex LiAlCl4·SO2 has been studied using a molecular dynamics method. A lithium cation is coordinated by one atom of Cl of the anion AlCl4- and one oxygen atom of SO2. The coordination number of lithium ions of LiAlCl4·SO2 is 4. The lithium cation is coordinated by three anions of AlCl4- and one molecule of SO2. Anion AlCl4- acts as a bridging ligand and binds different lithium cations.

Self‐Assembled Monolayer in Hybrid Quasi‐Solid Electrolyte Enables Boosted Interface Stability and Ion Conduction

AbstractComplex interactions between the inorganic solid electrolyte (ISE) and the liquid electrolyte (LE) give rise to challenges of achieving durable interface stability in hybrid quasi‐solid electrolytes (HQSE), and the influence on the involved ISE surface ionic conductivity also needs to be investigated. Here, 4‐chlorobenzenesulfonic acid (CBSA) is utilized to establish a self‐assembled monolayer (SAM) on the surface of Li6.4La3Zr1.4Ta0.6O12 (LLZTO), which is then incorporated into PEGDA‐based in situ polymerized HQSE. The results show that the introduction of CBSA significantly improves the LLZTO/LE interface stability with the optimized solvation structure, resulting in a favorable ionic conductivity (1.19 mS⋅cm−1) and an increasing Li+ transference number (0.647). Mechanisms for the promotion of ionic conduction and interfacial stability of SAM‐HQSE are unveiled through the density functional theory (DFT) combined with Raman spectra and 7Li solid‐state nuclear‐magnetic‐resonance. There are no short‐circuits in the Li|SAM‐HQSE|Li cells after 1000 h. The LFP|SAM‐HQSE|Li cells or LFP|SAM‐HQSE|Graphite pouch cells respectively achieve the capacity retention of 91.2 % and 87.0 % with the 0.5.C‐rate for 500 and 300 cycles. This facile and effective strategy proposed in this work make it accessible for constructing the stable surface micro‐environments of LLZTO where boost and homogenize the Li+ conduction in a hybrid quasi‐solid electrolyte system.

Self-Assembled Monolayer in Hybrid Quasi-Solid Electrolyte Enables Boosted Interface Stability and Ion Conduction.

Complex interactions between the inorganic solid electrolyte (ISE) and the liquid electrolyte (LE) give rise to challenges of achieving durable interface stability in hybrid quasi-solid electrolytes (HQSE), and the influence on the involved ISE surface ionic conductivity also needs to be investigated. Here, 4-chlorobenzenesulfonic acid (CBSA) is utilized to establish a self-assembled monolayer (SAM) on the surface of Li6.4La3Zr1.4Ta0.6O12 (LLZTO), which is then incorporated into PEGDA-based in situ polymerized HQSE. The results show that the introduction of CBSA significantly improves the LLZTO/LE interface stability with the optimized solvation structure, resulting in a favorable ionic conductivity (1.19 mS⋅cm-1) and an increasing Li+ transference number (0.647). Mechanisms for the promotion of ionic conduction and interfacial stability of SAM-HQSE are unveiled through the density functional theory (DFT) combined with Raman spectra and 7Li solid-state nuclear-magnetic-resonance. There are no short-circuits in the Li|SAM-HQSE|Li cells after 1000 h. The LFP|SAM-HQSE|Li cells or LFP|SAM-HQSE|Graphite pouch cells respectively achieve the capacity retention of 91.2 % and 87.0 % with the 0.5.C-rate for 500 and 300 cycles. This facile and effective strategy proposed in this work make it accessible for constructing the stable surface micro-environments of LLZTO where boost and homogenize the Li+ conduction in a hybrid quasi-solid electrolyte system.

Metal-Organic Coordination Enhanced Metallopolymer Electrolytes for Wide-Temperature Solid-State Lithium Metal Batteries.

The practical application of polymer electrolytes is seriously hindered by the inferior Li+ ionic conductivity, low Li+ transference number (tLi+), and poor interfacial stability. Herein, a structurally novel metallopolymer is designed and synthesized by exploiting a molybdenum (Mo) paddle-wheel complex as a tetratopic linker to bridge organic and inorganic moieties at molecular level. The prepared metallopolymer possesses combined merits of outstanding mechanical and thermal stability, as well as a low glass transition temperature (Tg <-50 °C). Based on this metallopolymer, an advanced metal-organic coordination enhanced metallopolymer electrolyte (MPE) is developed for constructing high-performance solid-state lithium metal batteries (LMBs). Due to the unsaturated coordination of Mo atoms, the uniformly distributed Mo-polyoxometalates (Mo-POMs) in metallopolymer skeleton can effectively immobilize anions (bis(fluorosulfonyl)imide anions, FSI-) and promote the dissociation of Li salts. Moreover, dynamic metal-organic coordination bonds endow the MPE with re-processability and self-healing, enabling it to accommodate electrode volume changes and maintain good interfacial contact. Consequently, the MPE achieves a competitive ionic conductivity of 0.712 mS cm-1 (25 °C), a high tLi+ (0.625), and a wide electrochemical stability window (>5.0 V). This study presents a unique MPE design based on metal-organic coordination enhanced strategy, providing a promising solution for developing wide-temperature solid-state LMBs.

Flexible and Compact PVDF/PMMA-Based Gel Polymer Electrolytes for High-Performance Sodium Metal Batteries.

Sodium is gaining recognition as a promising alternative to lithium for battery applications, particularly in sodium metal batteries (SMBs), where the performance is critically influenced by the choice of electrolyte. Although conventional organic liquid electrolytes are widely used, they pose significant issues. Gel membrane (GM)-based electrolytes have demonstrated enhanced reliability and stability. Nevertheless, there remains a pressing need to improve their electrochemical and mechanical properties to fulfill the demands of next-generation batteries, which require extended lifespan, rapid charging capabilities, and excellent flexibility. To address these challenges, a compact and flexible GM is developed by gelating a cast Polyvinylidene fluoride (PVDF)/Polymethyl methacrylate (PMMA) blend film. The resulting GM possesses a suitable sodium ionic conductivity of 0.507 mS cm-1 and an impressive ion transference number of 0.47, enabling dendrite-free reversible sodium plating and stripping for up to 300 h at a current density of 0.8 mA cm-2. Furthermore, the effectiveness of sodium dendrite suppression is demonstrated in Na/GM/Na3V2(PO4)3 cells, which exhibit a high discharge capacity and excellent cycling stability. The flexible SMB retains stable voltage output and continues to function even when bent or twisted. This study introduces a novel strategy for creating gel electrolytes for high-performance flexible SMBs.

From trips to stages: a methodology for Generating Stage Information in trip-level Household travel surveys

AbstractTrip-level household travel surveys (HTS) are an efficient and widely used instrument in transport planning and research and are expected to remain in this role for at least the near future. Mode information is typically assigned to trips in these surveys based on a hierarchy of transport modes that hides important information on the individual stages which is particularly relevant for walking. This study develops a methodology for estimating detailed stage-level information for trip-level HTS that contain some information on stages, this is the sequence of used transport modes and the number of transfers in Public Transport (PT) trips. The methodology is developed based on detailed stage-level data from a sub-sample in the German National HTS MiD 2017 and directly applied to the German city-based HTS SrV 2018 which is a trip-level survey but contains stage-level information on modes and PT transfers. Linear Regression Models for estimating walking stage duration in PT and car trips are combined with simple heuristic estimations for the less frequent types of intermodal trips. Trip purpose, accompaniment and total trip duration are important predictors for walking stage duration. Trip-level and stage-level modal-split figures for the number, duration, and distance of trips and stages in SrV 2018 are computed with the developed methodology. About half of all stages and 30% of trips are done by walking. Walking stage duration is with around 38% considerable, this share drops to around 12% for walking stage distance.

Pressure-directed enhanced ionic conductivity in MgMoO4 mixed-phases

The mixed conductors have attracted much attention for potential applications in fuel cells, sensors, supercapacitors. Here, the electrical transport behavior of MgMoO4 were systematically investigated at pressures up to 30.0 GPa using impedance spectroscopy measurements and theoretical calculations. The discontinuous changes in electrical parameters reflect the pressure-induced phase transition from β-MgMoO4 to γ-MgMoO4. The transport mechanism was determined to be mixed ionic-electronic conduction, and the contributions of carriers were distinguished. In the pressure range where the low- and high- pressure phase coexist, ionic transport plays a dominant role. The optimal solution for ionic conductivity of MgMoO4 occurs in the mixed phases, and the ionic conductivity has been increased by two orders of magnitude in comparison to that observed at ambient conditions. The resistances were analyzed with band gap, transference number and the relative ionic diffusion coefficient. The pressure constrains the atomic amplitude and limits ion-phonon scattering, resulting in a significant enhancement of the ionic diffusion coefficient and facilitates the ionic conduction of γ-MgMoO4. Meanwhile, it is found that the grain boundary response was weakened under compression, and the static dielectric constant was improved by pressure. These results offer valuable insights for optimizing and applying ABO4-based mixed conductors.

Single ion conducting gel polymer electrolytes containing polybenzimidazole-based ionomers with abundant Li+ transport channels for dendrite-free lithium metal batteries

Single ion conducting polymer electrolytes (SIPEs) have attracted much attention due to their ability to effectively inhibit the growth of lithium dendrites, but still confront the problems of low ionic conductivity and poor mechanical properties. In this study, a new polybenzimidazole-based ionomer (M-OPBI) is synthesized by chemically modifying aromatic poly(2,2′-(p-oxydiphenylene)-5,5′-bibenzimidazole) (OPBI), and two series of novel SIPEs (i.e. M-OPBI/PEO and M-OPBI/PVDF) are achieved after blending with different polymer matrices (i.e. poly(ethylene oxide) (PEO) and poly(vinylidene fluoride) (PVDF)). Afterwards, some single ion conducting gel polymer electrolytes (SIGPEs) with abundant Li+ transport channels are fabricated by absorbing appropriate amount of plasticizers. The imidazole anions and sulfonylimide anions in the ionomer present low binding energies with Li+, which is beneficial for the dissociation and transport of Li+. Moreover, in view of the presence of rigid aromatic structure in the main chain of the ionomer and the interactions between the polymers, polybenzimidazole-based SIPEs all exhibit excellent thermal and mechanical properties. Most importantly, in comparison with PVDF matrix, PEO is approved to be more compatible with the ionomer and provide additional Li+ conduction sites, and this will enhance the interfacial compatibility and facilitate the construction of abundant Li+ transport channels in M-OPBI/PEO membranes. As a result, M-OPBI/PEO-0.4 membrane shows the lowest activation energy of 0.098 eV, the highest room-temperature ionic conductivity of 9.9 × 10-5 S cM-1, and a satisfactory lithium ion transference number of 0.88. Thanks to these merits, the symmetric Li||Li cell assembled with M-OPBI/PEO-0.4 membrane exhibits an excellent reversible lithium plating/stripping performance without short circuit over 2160 h. This study provides a new design strategy for the development of SIGPEs for application in dendrite-free lithium metal batteries.

Enhanced H2O2 Production by Two-Electron Oxygen Reduction on Co3O4/MXene Catalyst

The two-electron oxygen reduction reaction (ORR) using an electrochemical method is considered a viable green technology for generating H2O2. Platinum group metals demonstrate excellent H2O2 generation performance due to their superior ORR activity and stability. However, the high cost of these electrocatalysts is a significant barrier to the widespread adoption of this technology, prompting research into non-precious metal catalysts as alternatives. In this work, Co3O4 nanoparticles with sized from 5 to 10 nm were synthesized on MXene sheets. Compared with Co3O4/C and MXene, the results indicated that Co3O4/MXene exhibited the best electrochemical performances, with an electron transfer number of ∼3.1 during oxygen reduction and an H2O2 selectivity of ∼47%. Co3O4/MXene also demonstrated great stability. After 5000 cycles, the H2O2 selectivity and electron transfer number remained at 50% and 3.0, respectively. After 12 h of continuous testing, Co3O4/MXene exhibited a high Faraday efficiency of 50% and H2O2 yield of 0.14 mol h−1 g−1, with H2O2 selectivity increasing to 68.7% and an electron transfer number of 2.6. The excellent electrochemistry is attributed to the synergistic effect between MXene and Co3O4. This study provides valuable insights into non-precious metal electrocatalysts for H2O2 generation.

Three-dimensional nanocomposites derived from combined metal organic frameworks doped with Ce, La, and Cu as a bifunctional electrocatalyst for supercapacitors and oxygen reduction reaction

Fabrication of a nanocomposite with a low-cost and efficient synthesis method instead of using electrocatalysts based on platinum metal has become one of the main challenges in energy storage devices and fuel cells. In this regard, a bifunctional electrocatalyst for supercapacitors and oxygen reduction reaction is fabricated and tested. The novelty of this study is the synthesis method and enhancement of the electrochemical characteristics of synthesized electrocatalysts. The core-shell method is used for the electrocatalyst's synthesis which uses Zeolitic Imidazolate Framework (ZIF)-8, ZIF-67, and Material Institute Lavoisiers (MIL)-101 for the fabrication of three types of electrocatalysts. In the following, to increase the characteristics such as conductivity and stability, doping of Copper (Cu), Cerium (Ce), and Lanthanum (La) are added to the nanocomposites. The Co@NC, CoZn@NC, and CoZn@FeNC prepared electrocatalysts are obtained from the pyrolyze process of La/ZIF-67, CeCu/ZIF-8@ La/ZIF-67, MIL-101@CeCu/ZIF-8/La/ZIF-67. The results indicated that the CoZn@NC electrocatalyst has the best performance in the oxygen reduction reaction (ORR) with an onset potential of 0.062 (V vs Ag/AgCl) and current density of −12.97 (mA/cm2) at a constant voltage of −1 V. Furthermore, the electron transfer number of CoZn@NC electrocatalyst for ORR was 3.64. The conducted Galvanostatic Charge-Discharge (GCD) tests demonstrated that the CoZn@NC electrode has the highest capacitance of 271.14 F/g. The outcomes showed that by the core-shell method, various properties of nanocomposites can be utilized to solve the weaknesses of catalysts by using proper metals. Moreover, the presence of Cu2+,Ce3+,La3+ improve the structural defects in the carbon matrix, the stability based on the chronoamperometry results, and the mass transfer. The study provides a perspective for future researches to fill the research gaps to obtain the new supercapacitors utilize on a large scale in the electronics industry.