Coulombic Efficiency Research Articles

The Reconstruction of Bi2Te4O11 Nanorods for Efficient and pH-universal Electrochemical CO2 Reduction.

The electrochemical CO2 reduction reaction (CO2RR) to generate chemical fuels such as formate presents a promising route to a carbon-neutral future. However, its practical application is hindered by the competing CO production and hydrogen evolution reaction (HER), as well as the lack of pH-universal catalysts. Here, Te-modified Bi nanorods (Te-Bi NRs) were synthesized through in situ reconstruction of Bi2Te4O11 NRs under the CO2RR condition. Our study illustrates that the complex reconstruction process of Bi2Te4O11 NRs during CO2RR could be decoupled into three distinct steps, i.e., the destruction of Bi2Te4O11, the formation of Te/Bi phases, and the dissolution of Te. The thus-obtained Te-Bi NRs exhibit remarkably high performance in CO2RR towards formate production, showing high activity, selectivity, and stability across all pH conditions (acidic, neutral, and alkaline). In a flow cell reactor under neutral, alkaline, or acidic conditions, the catalysts achieved HCOOH Faradaic efficiencies of up to 94.3 %, 96.4 %, and 91.0 %, respectively, at a high current density of 300 mA cm-2. Density functional theory calculations, along with operando spectral measurements, reveal that Te manipulates the Bi sites to an electron-deficient state, enhancing the adsorption strength of the *OCHO intermediate, and significantly suppressing the competing HER and CO production. This study highlights the substantial influence of catalyst reconstruction under operational conditions and offers insights into designing highly active and stable electrocatalysts towards CO2RR.

Self-Polycondensation Flux Synthesis of Ultrastable Olefin-Linked Covalent Organic Frameworks for Electrocatalysis.

Creating new functional materials that efficiently support noble metal catalysts is important and in high demand. Herein, we develop a self-polycondensation flux synthesis strategy that can produce olefin-linked covalent organic framework (COF) platforms with high crystallinity and porosity as the supports of Pd nanoparticles for electrocatalytic nitrogen reduction reaction (ENRR). A series of "two in one" monomers integrating aldehyde and methyl reactive groups are rationally designed to afford COFs with square-shaped pores and ultrahigh chemical stability (e.g., strong acid or alkali environments for >1 month). Functionalizing Fluorine significantly boosts the hydrophobicity of fluoro-functionalized COFs, which can inhibit the competing hydrogen evolution reaction (HER) and enhance ENRR performances. The COFs loading Pd nanoparticles show high NH3 production yields up to 90.0 ± 2.6 μg·h-1·mgcat.-1 and the faradaic efficiency of 44% at -0.2 V versus reversible hydrogen electrode, the best comprehensive performance among all reported COFs. Meanwhile, the catalysts are easy to recover and recycle, as demonstrated by their use for 15 cycles and 17 hours, with good performance retention. This work not only provides a new synthesis strategy for olefin-linked COFs, but also paves a new avenue for the design of highly efficient ENRR catalysts.

Conversion of Nitrate to Ammonia by Amidinothiourea-Coordinated Metal Molecular Electrocatalysts with d-π Conjugation.

The electrochemical reduction of nitrate to ammonia (NO3RR) provides a desired alternative of the traditional Haber-Bosch route for ammonia production, igniting a research boom in the development of electrocatalysts with high activity. Among them, molecular electrocatalysts hold considerable promise for the NO3RR, suppressing the competing hydrogen evolution reaction. However, the complicated synthesis procedure, usage of environmentally unfriendly organic solvents, and poor stability of Cu-based molecular electrocatalysts greatly limit their employment in NO3RR, and the development of desired Cu-based molecular catalysts remains challenging. Herein, a simple nonorganic solvent involving a one-step strategy was proposed to synthesize d-π-conjugated molecular electrocatalysts metal-amidinothiourea (M-ATU). Cu-ATU is composed of Cu coordinated with two S and two N atoms, whereas Ni-ATU is formed by Ni with four N atoms from two ATU ligands. Remarkably, Cu-ATU with a Cu-N2S2 coordination configuration exhibits superior NO3RR activity with a NH3 yield rate of 159.8 mg h-1 mgcat-1 (-1.54 V) and Faradaic efficiency of 91.7% (-1.34 V), outperforming previously reported molecular catalysts. Compared to Ni-ATU, Cu-ATU transfers more electrons to the *NO intermediate, effectively breaking the strong sp2 hybridization system and weakening the energy of N═O bonds. The increase in free energy of *NO reduced the energy barriers of the rate-determining step, facilitating the further hydrogenation process over Cu-ATU. Our work opened up a new horizon for exploring molecular electrocatalysts for nitrate activation and paved a way for the in-depth understanding of catalytic behaviors, aligning more closely with industrial demands.

Hydrophobic assembly of molecular catalysts at the gas-liquid-solid interface drives highly selective CO2 electromethanation.

Molecular catalysts offer tunable active and peripheral sites, rendering them ideal model systems to explore fundamental concepts in catalysis. However, hydrophobic designs are often regarded as detrimental for dissolution in aqueous electrolytes. Here we show that established cobalt terpyridine catalysts modified with hydrophobic perfluorinated alkyl side chains can assemble at the gas-liquid-solid interfaces on a gas diffusion electrode. We find that the self-assembly of these perfluorinated units on the electrode surface results in a catalytic system selective for electrochemical CO2 reduction to CH4, whereas every other cobalt terpyridine catalyst reported previously was only selective for CO or formate. Mechanistic investigations suggest that the pyridine units function as proton shuttles that deliver protons to the dynamic hydrophobic pocket in which CO2 reduction takes place. Finally, integration with fluorinated carbon nanotubes as a hydrophobic conductive scaffold leads to a Faradaic efficiency for CH4 production above 80% at rates above 10 mA cm-2-impressive activities for a molecular electrocatalytic system.

Hierarchical Assembly of High-Nuclearity Copper(I) Alkynide Nanoclusters: Highly Effective CO2 Electroreduction Catalyst toward Hydrocarbons.

The pursuit of precision in the engineering of metal nanoparticle assemblies has long fascinated scientists, but achieving atomic-level accuracy continues to pose a significant challenge. This research sheds light on the hierarchical assembly processes of two high-nuclearity Cu(I) nanoclusters (NCs). By employing a multiligand cooperative stabilization strategy, we have isolated a series of thiacalix[4]arene (TC4A)/alkynyl coprotected Cu(I) NCs (Cux, where x = 9, 13, 17, 22). These NCs are intricately coassembled from the fundamental building units of {Cu4(TC4A)} and alkynyl-stabilized Cu5L6 in various ratios. By capturing active anion templates such as O2-, Cl-, or C22- that are generated in situ, we have further explored the secondary structural self-assembly of these clusters. Cu13 serves as a secondary assembly module for constructing Cu38 and Cu43, which exhibit the highest nuclearity reported to date among Cu(I) NCs encased in macrocyclic ligands. Notably, Cu38 demonstrates an impressive Faradaic efficiency of 62.01% for hydrocarbons at -1.57 V vs RHE during CO2 electroreduction, with 34.03% for C2H4 and 27.98% for CH4. This performance establishes it as an exceptionally rare, large, atomically precise metal NC (nuclearity >30) capable of catalyzing the formation of highly electro-reduced hydrocarbon products. Our research has introduced a new approach for constructing high-nuclearity Cu(I) NCs through a hierarchical assembly method and investigating their potential in the electrocatalytic transformation of CO2 into hydrocarbons.

Toward the Rechargeable Aqueous Zinc Ion Batteries with Improved Overall Performance: Electrolyte with Surface Adsorptive Additive.

Aqueous zinc-ion batteries (AZIBs) with slightly acidic electrolytes process advantages such as high safety, competitive cost, and satisfactory electrochemical performance. However, the failure behaviors of both electrodes, regarding zinc dendrite growth, interfacial parasitic reactions, and the collapse of cathode materials hinder the practical application of ZIBs. To alleviate the issues of both anode and cathode at the same time, D-xylose (DX) is introduced to the electrolyte as a multifunctional additive. As a result, the side reaction of the anode is suppressed and the metallic deposition behavior is regulated due to the hydrogen bonding network reconstruction and preferential surface adsorption of DX; for the MnO2 cathode, the DX adsorption can help the interfacial charge transfer and increase the reactive sites. Benefiting from these merits, DX-optimized Zn//Zn battery displays reveal a prolonged lifespan of 6912h and an ultra-high cumulative capacity of 17.28Ahcm-2 at 5mAcm-2. With the function of water reactivity suppression, the Coulombic efficiency reaches 99.91% at 2mAcm-2; the Zn||MnO2 full batteries exhibit excellent cyclability over 2000 cycles at 5C with an increased capacity of 118.9mAhg-1, indicating the dual functions to both of the electrodes for AZIBs.

Synthesis and Fabrication of Metal Cation Intercalation in Multilayered Ti3C2Tx Composite CNF Electrode for Asymmetric Coin Cell Supercapacitors.

Ti3C2Tx has attracted considerable attention from researchers in energy storage due to its unique structure and beneficial surface functional group characteristics. Recent studies have focused extensively on developing Ti3C2Tx composites to create potential electrode materials for energy storage applications. Carbon nanofiber is often combined with Ti3C2Tx to produce high-performance functional nanocomposites, effectively harnessing the unique properties of Ti3C2Tx nanosheets while ensuring exceptional electrochemical behavior. This work employs an ultrasonication method to prepare a Na-Ti3C2Tx/CNF electrode. Establishing a stable interlayer structure between Ti3C2Tx nanosheets and cationic metal intercalation materials is crucial for expanding the interlayer spacing of Ti3C2Tx and creating multidirectional stable ion transport channels. Consequently, this process exposes more active sites that are accessible to ions. At a current density of 1 A g-1, the resulting Na-Ti3C2Tx/CNF demonstrates an impressive specific capacitance of 680.2 F g-1. Notably, the asymmetric supercapacitor assembled with Na-Ti3C2Tx/CNF as the positive electrode and activated carbon as the negative electrode exhibits remarkable cyclic retention of 83.1% and the Coulombic efficiency of 90.5% after 10,000 cycles at 10 A g-1, a wide voltage window of 1.5 V, a high energy density of 102.5 W h kg-1, and a power density of 2963.7 W kg-1. The fabricated coin cell ASC devices, which include glowing red light-emitting diodes, were demonstrated in practical applications. The optimization strategy for developing Na-Ti3C2Tx/CNF provides essential technical support for integrating Na-Ti3C2Tx/CNF into the next generation of portable and adaptable wearable electrochemical energy storage devices.

Copper–nickel–MOF/nickel foam catalysts grown in situ for efficient electrochemical nitrate reduction to ammonia

Reducing nitrate (NO3−) in an aqueous solution to ammonia under ambient conditions can provide a green and sustainable NH3‐synthesis technology and mitigate global energy and pollution issues. In this work, a CuNi0.75–1,3,5‐benzenetricarboxylic acid/nickel foam (CuNi0.75–MOF/NF) catalyst grown in situ was prepared via a one‐pot method as an efficient cathode material for electrocatalytic nitrate reduction reaction (NO3RR). The CuNi0.75–MOF/NF catalyst exhibited excellent electrocatalytic NO3RR performance at −1.0 V versus a reversible hydrogen electrode, achieving an outstanding faradaic efficiency of 95.88 % and an NH3 yield of 51.78 mg h−1 cm−2. The 15N isotope labeling experiments confirmed that the sole source of N in the electrocatalytic NO3RR was the NO3− in the electrolyte. The reaction pathway for the electrocatalytic NO3RR was derived by in situ Fourier transform infrared spectroscopy and in situ differential electrochemical mass spectrometry. Density functional theory calculations revealed that the Ni element in the CuNi0.75–MOF/NF catalyst had excellent O–H activation ability and strong *H adsorption capacity. These *H species were transferred from the Ni sites to the *NO adsorption intermediates located on the Cu sites, providing a continuous supply of *H to Cu, thereby promoting the formation of *NOH intermediates and enhancing the hydrogenation process of the electrocatalytic NO3RR.

Voltage-Driven Molecular Photoelectrocatalysis of Water Oxidation.

Molecular photocatalysis and photoelectrocatalysis have been widely used to conduct oxidation-reduction processes ranging from fuel generation to electroorganic synthesis. We recently showed that an electrostatic potential drop across the double layer contributes to the driving force for electron transfer (ET) between a dissolved reactant and a molecular catalyst immobilized directly on the electrode surface. In this article, we report voltage-driven molecular photoelectrocatalysis with a prevalent homogeneous water oxidation catalyst, (bpy)Cu (II), which was covalently attached to the carbon surface and exhibited photocatalytic activity. The strong potential dependence of the photooxidation current suggests that the electrostatic potential drop across the double layer contributes to the driving force for ET between a water molecule and the excited state of surface-bound (bpy)Cu (II). Scanning electrochemical microscopy (SECM) was used to analyze the products and determine the faradaic efficiencies for the generation of oxygen and hydrogen peroxide. Unlike electrocatalytic water oxidation by (bpy)Cu (II) in the dark, which produces only O2, the voltage-driven photooxidation includes an additional 2e- pathway generating H2O2. DFT calculations show that the applied voltage and the presence of light can alter the activation energy for the rate-determining water nucleophilic attack steps, thereby increasing the reaction rate of photo-oxidation of water and opening the 2e- pathway. These results suggest a new route for designing next-generation hybrid molecular photo(electro)catalysts for water oxidation and other processes.

Air-Stable Membrane-Free Magnesium Redox Flow Batteries.

Membrane-free biphasic self-stratified batteries (MBSBs) utilizing aqueous/nonaqueous electrolyte systems have garnered significant attention owing to their flexible manufacturing and cost-effectiveness. In this study, we present an ultrastable high-voltage Mg MBSB based on an aqueous/nonaqueous electrolyte system. The engineered aqueous electrolyte had a wide electrochemical stability window of 3.24 V. The Mg metal anode features a Mg2+-conductive protective coating. Two metal-free redox compounds, 2,2,6,6-tetramethylpiperdinyl oxy (TEMPO) and N-propyl phenothiazine (C3-PTZ), were used as catholytes. The Mg||TEMPO and Mg||C3-PTZ MBSBs exhibited high cell voltages of 2.07 and 2.12 V, respectively, and were studied under static, stirred, and flow conditions. The Mg MBSBs were initially evaluated at different catholyte concentrations (0.1, 0.3, and 0.5 M) under static conditions. Notably, the Mg||TEMPO (0.5 M) and Mg||C3-PTZ (0.5 M) static batteries maintained exceptional performances over 500 cycles at 8 mA/cm2, with capacity retention rates of 97.84% and 98.87%, Coulombic efficiencies of 99.17% and 99.12%, and capacity utilization of 70.2% and 71.3%, respectively. Under stirred and flow conditions, the Mg||TEMPO (0.5 M) and Mg||C3-PTZ (0.5 M) batteries cycled 500 times at 12 mA/cm2 demonstrated capacity retention rates of 99.82% and 99.88% (stirred), 93.58% and 92.16% (flow), respectively. Under flow conditions, the Mg||TEMPO (0.5 M) and Mg||C3-PTZ (0.5 M) batteries demonstrated power densities of 195 and 191 mW/cm2, respectively, surpassing those of 139 and 144 mW/cm2 under static conditions. These cost-effective Mg MBSBs exhibit remarkable performance and advance the application of Mg chemistry in organic flow batteries.

Li-Fe-Cl Families as Novel Solid Electrolytes for All-Solid-State Batteries.

The halides have attracted much attention as novel solid electrolytes because of their easy synthesis, high electrochemical stability, and high ionic conductivities. However, the reported halides for solid electrolytes are still understudied compared with the oxides and sulfides. Here, we studied the Li-Fe-Cl phases that include Li2FeCl4 and Li6FeCl8. Using the self-doping approach, a maximum ionic conductivity of 2.0 × 10-4 S cm-1 at 50 °C was achieved for Li1.8Fe1.1Cl4. It was improved by 3 orders of magnitude compared with that of Li2FeCl4 (8.27 × 10-7 S cm-1 at 50 °C). For the Li|Li1.8Fe1.1Cl4|Li half-cell, it cycled for 2000 h at 50 °C under a current density of 0.01 mA cm-2, indicating an acceptable compatibility between Li2FeCl4 and Li. Finally, an all-solid-state battery was successfully assembled with Li1.8Fe1.1Cl4@LFP as the cathode, Li1.8Fe1.1Cl4 as the electrolyte, and a Li sheet as the anode. The initial specific charge capacity of the battery was 76.36 mAh g-1 at 0.1C and 50 °C. The initial Coulombic efficiency was 73.06%. This study suggests Li2FeCl4 as a new solid electrolyte, and the introduction of Li vacancies into the Li site is an efficient way to improve the electrochemical properties of halides.

Hierarchically Ordered Pore Engineering of Carbon Supports with High-Density Edge-Type Single-Atom Sites to Boost Electrochemical CO2 Reduction.

Metal sites at the edge of the carbon matrix possess unique geometric and electronic structures, exhibiting higher intrinsic activity than in-plane sites. However, creating single-atom catalysts with high-density edge sites remains challenging. Herein, the hierarchically ordered pore engineering of metal-organic framework-based materials to construct high-density edge-type single-atomic Ni sites for electrochemical CO2 reduction reaction (CO2RR) is reported. The created ordered macroporous structure can expose enriched edges, further increased by hollowing the pore walls, which overcomes the low edge percentage in the traditional microporous substrates. The prepared single-atomic Ni sites on the ordered macroporous carbon with ultra-thin hollow walls (Ni/H-OMC) exhibit Faraday efficiencies of CO above 90% in an ultra-wide potential window of 600mV and a turnover frequency of 3.4×104h-1, much superior than that of the microporous material with dominant plane-type sites. Theory calculations reveal that NiN4 sites at the edges have a significantly disrupted charge distribution, forming electron-rich Ni centers with enhanced adsorption ability with *COOH, thereby boosting CO2RR efficiency. Furthermore, a Zn-CO2 battery using the Ni/H-OMC cathode shows an unprecedentedly high power density of 15.9mW cm-2 and maintains an exceptionally stable charge-discharge performance over 100h.

Investigation of polypyrrole based composite material for lithium sulfur batteries

With the rising demand for electricity storage devices, the performance requirements for such equipment have become increasingly stringent. Lithium-sulfur (Li-S) batteries are poised to be among the next generation of energy storage systems. However, before they can be commercially viable, several challenges must be addressed, including low sulfur conductivity and the shuttle effect. Herein, polypyrrole based sulfur composite was prepared by simple method in hydrothermal teflon lined autoclave for Li-S battery. The S/SP/ppy/PVDF electrode exhibited the initial discharge capacity of 662 mAh g− 1 at 0.5 C and 637 mAh g− 1 after 100 cycles. The Coulombic efficiency was 96% all along charge/discharge cycling. Moreover, Li-S coin cells were assembled and tested to demonstrate the potential application and scale-up of the polypyrrole-sulfur composite.

Chiral Nanostructured Ag Films for Multicarbon Products from CO2 Electroreduction.

The formation of multicarbon products from CO2 electroreduction is challenging on materials other than Cu-based catalysts. Ag has been known to be a typical metal catalyst, producing CO in CO2 electroreduction. The formation of C2+ products by Ag has never been reported because the carbon-carbon (C-C) coupling is an unfavorable process due to the high reaction barrier energy of *OCCO. Here, we propose that the chirality-induced spin polarization of chiral nanostructured Ag films (CNAFs) can promote the formation of triplet OCCO by regulating its parallel electron spin alignment, and the helical lattice distortion of nanostructures can decrease the reaction energy of *OCCO, which triggers C-C coupling and promotes subsequent *OCCO hydrogenation to facilitate the generation of C2+ products. The CNAFs with helically lattice-distorted nanoflakes were fabricated via electrodeposition using phenylalanine as the symmetry-breaking agent. C2+ products (C2H4, C2H6, C3H8, C2H5OH, and CH3COOH) with a Faradaic efficiency of ∼4.7% and a current density of ∼22 mA/cm2 were generated in KHCO3 electrolytes under 12.5 atm of CO2 (g). Our findings propose that the chiral nanostructured materials can regulate the multifunctionality of catalytic performance in the catalytic reactions with triplet intermediates and products.

Wet Chemical Method ZnF2 Interlayer for High Critical Current Density Lithium Metal Batteries Utilizing Ba and Ta–Doped Li7La3Zr2O12 Garnet Solid Electrolyte

AbstractLi metal batteries with garnet‐type solid electrolytes have the potential to increase specific energy and power densities of current Li‐ion batteries. Li metal batteries have been hampered by the poor wettability of solid electrolyte with elemental lithium. Here, to resolve the solid garnet electrolyte/Li interface issue, a scalable, cost‐effective, and efficient surfactant‐assisted wet‐chemical strategy is developed. A ZnF2 interlayer coating is applied on Ba and Ta ‐co‐doped Li7La2.75Ba0.25Zr1.75Ta0.25O12 that formed LiF and Li‐Zn alloy upon contact with molten Li. Conformal contact applying a homogenous surfactant‐assisted ZnF2 coating reduced the interfacial resistance from 87 to 15.5 Ω cm2 which enhanced critical current density to a record high value of 5 mA cm−2 at room temperature. Dense and Li2CO3 free garnet solid electrolyte assisted in achieving long‐term stability for 1000 cycles at 1 mA cm−2. Interface stabilized Li/ZnF2‐ solid electrolyte/liquid electrolyte/LiFePO4 cell displayed a 90% capacity retention over 800 cycles at 0.2 C, with Coulombic efficiency of 99% as well as excellent cycle stability at 1 C, with ≈91% of capacity retention for 500 cycles. Using a new design principle for Li anode interfaces, next‐generation power‐intensive and stable solid‐state Li metal batteries can be developed.

Unveiling the Microscopic Origin of Ultrahigh Initial Coulombic Efficiency of High-Entropy Metal-Organic Frameworks for Sodium Storage.

The initial irreversible capacity loss during the first charging process largely reduces the affordable energy and power density of sodium storage devices, and developing advanced materials is the efficient way to solve this problem, which is fraught with challenges. Herein, inspired by theoretical calculations and the high-entropy concept, a series of fewer layers of high-entropy metal-organic frameworks (FLHE-MOFs) are successfully fabricated, delivering an ultrahigh initial Coulombic efficiency (ICE) of 86.1% and excellent cycling performance, which is far more than that of the other electrode materials (generally <70%). Greatly, the storage behavior of high-, medium-, and low-entropy MOFs is clarified by theoretical calculations and in-/ex-situ characterization, revealing that Co and Fe species can provide substantial sodium storage sites and largely enhance the charge transfer rate, whereas high-entropy effect can enable structural reversibility. Sodium ion capacitors constructed with FLHE-MOFs as the anode can provide an ultrahigh energy density of 121.8 W h kg-1 (200 W kg-1) and an extremely long-term cycle lifespan. This work not only breaks the limitation of MOF materials with poor performance for sodium storage but also provides an effective strategy for the fabrication and application of high-performance MOF-based anode materials with high ICE, in which this idea may also be applied in other fields.

In-series all-solid-state anode-less cells

Sustainable all-solid-state anode-less batteries may become critical for eliminating the challenges in traditional batteries. However, conditioning these batteries is a herculean challenge. In this study, anode-less cells were fabricated with single architectures, Cu/ZnO/Li2.99Ba0.005ClO/LiFePO4 or Cu/Li2O/Li2.99Ba0.005ClO/LiFePO4, and batteries of their off with two and three cells in series. Single- and multiple-cell batteries can undergo electrochemical cycles without requiring applied pressure while operating safely and inexpensively with viable materials at room temperature. All the batteries in this study did not require an inert atmosphere to be fabricated since no lithium metal was used a priori, which is a significant step toward sustainability, cost reduction, and scalability. The single cells featured a Li-anode nucleation layer of ZnO or Li2O doctor bladed on the negative current collector's surface. The maximum voltage accomplished in single cells was 3.2 V (with Li2O). Based on the most favorable capacity performance determined through electrochemical analysis, batteries incorporating two and three cells were assembled and connected in series, each integrating a ZnO layer, which enables the cell to achieve higher energy density. The two-cell battery achieves a maximum capacity of 6 mAh.g−1cathode, corresponding to a lithium discharged thickness of 0.369 μm, a maximum Coulombic efficiency CE of 34 %, almost half the CE of the single cell (76 %). Still, it is able to cycle for 18 cycles which is nearly the same number as a single cell. It is noteworthy that the internal resistance increases Ri,total = Ri,1 + Ri,2, while the capacitance decreases Ceq = C1C2/(C1 + C2), in two, or more, cells in series, in detriment to the capacity of the cell. The batteries, composed of three cells, cycled for 16 cycles to successfully power LEDs of different colors, finally showing a terminal potential of 5.3 V (1.8 V per cell). The groundbreaking finding in this study stems from assembling performing anode-less cells in series, representing a significant step forward in validating the viability of these cells for industrial applications. However, at the present power and energy densities, a long path is left to overcome until these cells are ready to serve in everyday use.

Degradation effect on oxidation of 5-hydroxymethyl-2-furaldehyde over cobalt-iron electrocatalysts in alkaline condition

Nowadays, the excessive utilization of fossil-based chemicals has caused serious environmental problems, especially due to the negative carbon footprints. Addressing this issue by substituting fossil resources with environmentally friendly biomass is imperative. This study focuses on the electrooxidation of 5-hydroxymethyl-2-furaldehyde (HMF), a biomass-derived chemical, into 2,5-furandicarboxylic acid (FDCA) in alkaline solutions, a crucial feedstock, for the chemical industry. Given the acknowledged instability of HMF in an alkaline environment, this research investigated the kinetic approximation of HMF degradation under varying concentrations of KOH solutions (0.1M and 1M KOH) over 12hours. Then, the electrooxidation of HMF to FDCA over cobalt-iron-based catalysts was investigated. As a result, the FDCA was successfully produced in 0.1M KOH solution with a remarkable yield of up to 94%, while a higher concentration (1M KOH solution) accelerated the electrooxidation process. However, the yield and Faradaic efficiency could be greatly dropped after 12hours of storing time due to the effects of HMF degradation reactions (Cannizaro and polymerization reactions). Therefore, this degradation phenomenon should be considered on an industrial scale, particularly when HMF may be stored for an extended period before utilization.

Porous activated carbon integrated carbon nitride nanosheets as functionalized separators for the efficient polysulfide entrapment in Li[sbnd]S batteries

Electrification of vehicles, hybrid aircraft and the advancement of portable electronics are exacting the deployment of high energy-dense batteries. The high theoretical capacity of sulfur (1675 mAh g−1), cost-effectiveness and environmental benignity of the lithium‑sulfur batteries (LSBs) are propitious for electrochemical energy storage beyond Li-ion battery technology. In this work, we described a simple, scalable preparation and electrochemical performance of porous activated carbon (PC)-infused graphitic carbon nitride (GCN) nanosheets with various ratios (PC@GCN 11, PC@GCN 12 and PC@GCN 21) as a polysulfide anchoring functionalized separator for LSBs. The high specific area (822 m2/g), hetero porosity, conductive carbon framework, surface functionalities and enriched N-doping of the PC@GCN synergistically induce mitigation of polysulfides via chemical and physical adsorption pathways in LSBs. The PC@GCN 21 modified separator demonstrates a high initial discharge capacity of 1389 mAh g−1 at a 0.1C rate and exhibits better capacity retention over 500 cycles at a 1C rate (655 mAh g−1) with sulfur loading of 3.8 mg/cm2 accompanied by high coulombic efficiency (94 %). The assembled cell with high S-loading (5.12 mg/cm2) shows a high initial discharge capacity of 712 mAh g−1 at 0.1C rate conditions. High Li-ion transference number (0.714), stable shuttle current, minimal coulombic efficiency loss (0.84 %), low shuttle factor and negligible self-discharge behaviour support the superior performance of the PC@GCN 21 coated cells. This report demonstrates that combining the high surface area, non-polar porous carbon with polar graphitic carbon nitride is a practical approach for designing metal-free functionalized separators for energy-dense LSBs.

Selenate-based heterojunction with cobalt-nickel paired site for electrocatalytic oxidation of 5-hydroxymethylfurfural coupling water splitting to produce hydrogen

It is very appealing that 5-hydroxymethylfurfural (HMF) is electrocatalytical oxidized as 2,5-furandicarboxylic acid (FDCA) linking to non-classical cathodic hydrogen (H2) production. However, the electrocatalysts for electrocatalytic HMF oxidative reaction (e-HMFOR) have been facing low Faradaic efficiency (FE) and high water splitting voltage. Herein, we propose a strategy of the NiSeO3@(CoSeO3)4 heterojunction by constructing a Co-Ni paired site, where the Co site is in charge of adsorbing for HMF while the electrons are transferred to the Ni site, thus giving the NiSeO3@(CoSeO3)4 heterojunction superior electrocatalytic performances for e-HMFOR and water splitting. By optimizing conditions, the NiSeO3@(CoSeO3)4 heterojunction has high conversion of 99.7%, high selectivity of 99.9%, and high FE of 98.4% at 1.3 V, as well as low cell voltage of 1.31 V at 10 mA cm−2 in 1 M KOH + 0.1 M HMF. This study offers a potential insight for e-HMFOR to high value-added FDCA coupling water splitting to produce H2 in an economical manner.