Alkali Metal Ions Research Articles

Enhanced Alkali-Ion Adsorption in Strongly Bonded Two-Dimensional TiS2/MoS2 van der Waals Heterostructures

Despite their remarkable properties, many two-dimensional (2D) materials do not possess the desired characteristics to enhance the energy density, rate performance, and cycle life of batteries when used as standalone materials for battery electrodes. However, engineering 2D van der Waals (vdW) heterostructures by stacking different 2D materials offers new opportunities for battery electrodes, combining desirable features and overcoming the limitations of the constituent 2D layers. In this work, using first-principles calculations, we investigated the electronic structure, thermal stability, stress–strain response, alkali (Li/Na/K)-ion adsorption, and diffusion characteristics of 2D heterostructures of titanium disulfide (TiS2) and molybdenum disulfide (MoS2) monolayers with attractive applications in alkali-metal ion batteries (AMIBs). This work revealed relatively strong interlayer interactions in the heterostructure, resulting in significant enhancements in the adsorption of alkali ions compared to the respective monolayers. This work demonstrates that TiS2/MoS2 heterostructures offer excellent mechanical flexibility, increased strength, and greater strain endurance. The results indicate that TiS2/MoS2 heterostructures are promising materials for next-generation flexible anodes for AMIBs.

Cinnamoyl Dipyrromethenes as Fluorescence Zinc(II) Ion Sensor.

Friedel-Crafts acylation of dipyrromethane with cinnamoyl chloride was conducted to obtain dicinnamoyl dipyrromethane compounds 3 and 4. Both compounds were subsequently oxidized by DDQ to produce dicinnamoyl dipyrromethene ligands (DC-1 and DC-2). A large bathochromic shift compared to dipyromethene (D) was observed at 95 nm for DC-1 and 67 nm for DC-2. Both compounds showed remarkable chelation-enhanced fluorescence (CHEF) upon addition of zinc(II) ions. Similar to the quadrupolar system, DC-1 exhibited absorption and emission near the optical windows of the tissue. However, asymmetrical DC-2 had a better "turn-on" CHEF, with a fluorescence intensity that was 22 times higher than that of compound D. The DC-2 ligand also showed a limit of detection (LOD) of up to 3.0×10-8 M and selectivity toward zinc(II) ions compared to alkali and alkaline earth metal ions.

Structure and electrical properties of AM(PO3)4: A = Li, Na and M = Ce and Pr

In this manuscript, preparation, crystal structure and electrical properties of two types of AIMIII(PO3)4 metaphosphates, namely LiCe(PO3)4 and LiPr(PO3)4 (monoclinic, C2/c), and NaCe(PO3)4 (monoclinic, P21/n) have been reported. All the compounds were prepared by conventional solid-state reaction and characterized by powder X-ray diffraction. The electrical properties of these materials were studied by impedance spectroscopy. The dc-conductivity (σdc) of all compounds show similar increasing trend with temperature and is attributed mainly to the alkali metal ion diffusion. However, a discontinuity in the temperature dependent σdc is observed at higher temperature in all of them. The activation energy (eV) for alkali ion conductivity in LiCe(PO3)4, LiPr(PO3)4 and NaCe(PO3)4 respectively, is 1.14, 1.18 and 0.84, up to certain temperature (∼973K), and increases to 1.31, 1.35 and 1.51 at higher temperature. The analysis of ac-conductivity and modulus spectra indicated a correlated movement of ions in the structure. It is observed that structure and electrical properties of these metaphosphates are dependent more on the nature and ionic radii of the alkali ions than the rare-earth ions.

Quantitative assessment of the effects of zeolite alteration processes on deep clastic reservoirs – A case study of the Jiamuhe Formation in the Shawan Sag, Junggar Basin, China

Zeolite minerals are widely developed in clastic rock reservoirs around the world, and their behavior during diagenetic evolution affects the performance of the reservoirs. Zeolite can fill the primary intergranular pores in a cemented manner and can also undergo alteration and postdissolution to increase pores during the diagenesis process, while quantitative research is still quite limited at present. For this purpose, this paper takes the typical zeolite-rich Jiamuhe Formation (P1j) in the deep layer of the Shawan Sag, Junggar Basin, as an example and carries out a series of sedimentological, petrological, mineralogical and geochemical analyses to quantitatively evaluate the effect of zeolite alteration on the reservoir. The results indicate that the deep P1j reservoir contains fan-delta facies sandstone and conglomerate, and its storage space is mainly zeolite intercrystalline pores and remaining intergranular pores. The zeolite mineral type is almost all laumontite, with very low analcite and heulandite contents (<1%). The volcanic glass provided by the medium–basic volcanic rock debris (andesite and corresponding tuff), with the continuous increase in temperature and the supply of alkali metal ions, is eroded into laumontite via clinoptilolite and heulandite. In the process of zeolite alteration, zeolite minerals appear as zonal characteristics in the vertical direction. The intercrystalline pores formed by the dehydration of zeolite minerals are the most important factors for the development of high-quality deep reservoirs. Based on a large number of statistical analyses of zeolite cementation and intercrystalline pores within the cementation, a unit change of zeolite can cause a unit change in the intercrystalline pores of 22.16%. Supposing that the laumontite mineral content of the reservoir is 30%, the porosity can be increased by 6.6%. This can provide theoretical guidance for the change in the porosity of zeolite alteration in zeolite-rich reservoirs under similar backgrounds and improve the academic understanding of this point, which is exceedingly crucial. For instance, the Permian sand-conglomerate reservoirs in the northwestern margin of the Junggar Basin also have similar zeolite alteration pathways, and the porosity can be quantitatively increased by 8.8% (the zeolite cementation is approximately 40%). Laumontite (21%) in high-quality reservoirs of the Yingcheng Formation in the Changling Sag, Songliao Basin, can increase the porosity by 4.5%.

Tunable and facile preparation of chelate-based ionic liquids for highly efficient SO2 separation under low concentration in flue gas

A strategy for facile preparation of chelate-based ionic liquids (ILs) by simple chelation was developed, where a series of chelate-based ILs with tunable functionalized anions (azole), cheap ligands (PEG400), and simple metal ions (Li+, Na+, and K+) were designed for SO2 capture under 2000 ppm in flue gas. Both the anion-tunable strategy and the fine-tuned strategy were used to explore the effect of anions, ligands, and metal ions. The experimental absorptions, spectroscopic investigations, and DFT calculations indicated that the process of SO2 capture was mostly based on the nucleophilic effect of electronegative N site toward SO2. Furthermore, the tuning of alkali metal ions was proved to have little influence on SO2 absorption. The ideal IL, [Na(PEG400)][Tetz], exhibited splendid available absorption capacity of SO2 (0.57 mol/mol), excellent selectivity (63 under 2000 ppm SO2/15% CO2), and outstanding reversibility, indicating good potential for industrial application.

Design of Gradient Ti Reconstituted Fe2O3 Anodes with Enhanced Lithium Affinity Modulated Electronic Structures: First-Principles Calculations and Experiment Verification.

High-performance conversion transition metal oxides are strong candidates for advanced anode materials for lithium-ion batteries. However, the poor intrinsic conductivity and the large volume changes during battery operation are important constraints to its practical application. The heterogeneous atom doping strategy is an important way to modulate the electronic structure and surface states of the host materials. Herein, theoretical calculations reveal that heteroatomic Ti doping and its ionic or electronic compensation mechanisms can well modulate the electronic structure of Fe2O3 and change the surface Li-ion affinity. A Ti concentration gradient modification strategy for Fe2O3 is proposed to construct high-performance electrode materials. As a Li-ion battery anode, Ti concentration gradient-doped Fe2O3 achieves excellent long-cycle stability, with a reversible capacity of 1001.9 mAh g-1 at 1 A g-1 for 1200 cycles, and even maintains a reversible specific capacity compared to the theoretical capacity of commercial graphite electrodes at 2 A g-1 for 2000 cycles. This combination of theoretical calculations and experiments offers ways to intelligently design and develop alkali metal ion batteries.

Fusing thiadiazol and terephthalate: A concept to promote the electrochemical performance of conjugated dicarboxylates.

Organic electrode materials based on conjugated dicarboxylate moieties are particularly attractive to develop metal-ion organic batteries. Exhibiting good stability properties in liquid electrolytes, such organic electrode materials can reversibility store alkali metal ions (Li, Na or K) at low working potential. Although many molecular designs have been investigated in the last decade, conjugated dicarboxylates are impeded by low Coulombic efficiencies, especially at the first cycle, and sluggish kinetics in most cases. Herein, we report on a new strategy in the design of conjugated carboxylates by fusing a thiadiazole heterocycle to the terephthalate core. We investigate for the first time the synthesis and electrochemical performance of dilithium-2,1,3-benzothiadiazole-4,7-dicarboxylate (Li2-DCBTZ) as positive electrode material. Next to being a new structural design, the presence of the thiadiazole ring enables (i) a better conjugation of p-n electrons leading to a benefit in terms of rate capability, and (ii) a better stabilizing coordination network for Li ions through both oxygen and nitrogen atoms. In addition, the reduced state in Li4-DCBTZ is stabilized due to a maintained aromaticity in the heteroaromatic core in comparison to the parent terephthalate. Theoretical calculations on the Li-ion storage mechanism and bonding character support the experimental work.

Solid-Electrolyte Interphase Formation in Amide-Type Ionic Liquids in the Presence of Different Metal Cations

The formation of solid-electrolyte interphase (SEI) on a glassy carbon (GC) electrode in 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)amide (BMPFSA) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Li+, Na+, K+, and Ni2+ was investigated using the redox reaction of ferrocene (Fc). The anodic peak potential (E pa) for the oxidation of Fc changed after holding the electrode at –1.4 to –1.5 V vs Ag|Ag(I) in BMPFSA in the presence of the alkali metal ions. The decomposition of FSA– was confirmed by X-ray photoelectron spectroscopy (XPS) on a GC electrode held at –1.5 V vs Ag|Ag(I) for 6 h in BMPFSA containing the alkali metal ions. The change in E pa may also suggest the formation of homogeneous SEI in the FSA–-type ionic liquid. Moreover, E pa changed after holding the electrode at the potential more negative than –0.9 V vs Ag|Ag(I) in 50 mM Ni(TFSA)2/BMPTFSA while the decomposition of TFSA– was not confirmed by XPS on the electrode held at –1.1 V vs Ag|Ag(I) for 6 h, suggesting the bonds except C-F (e.g., S-C) were dissociated to form the SEI. Since the deposition potential of Ni in BMPTFSA was more negative than the SEI formation potential, the deposition of Ni may be inhibited by the SEI.

Ultrauniform Ru Nanoclusters as Efficient Hydrogenation Catalysts for Phthalates

Cyclohexane dicarboxylic acid (CHDA) ester, a kind of environmental-friendly plasticizer, can be produced by phthalates hydrogenation. However, the synthesis of catalysts with high activity and selectivity is a challenge due to the stability of aromatic rings. In this work, a series of ultrauniform Ru nanoclusters supported by γ-Al2O3 are synthesized for the hydrogenation of diisononyl phthalate (DINP). Results show that the conversion of DINP and the selectivity of diisononyl-cyclohexane-1,2-dicarboxylate (DINCH) both reach 100% at 140 °C and 3 MPa H2 pressure. Diisononyl-cyclohexene-1,2-dicarboxylate (4H-DINP) and 1,2-cyclohexanedicarboxylate-7-methyloctyl ester are found; the hydrogenation reaction network of DINP is constructed. Alkali metal ions adsorbed on the surface of Ru nanoclusters prepared by the polyol method can stabilize Ru3+-Hδ− species by electrostatic interaction, thus affecting the hydrogenation activity of the catalyst, following the order of Li+ > Na+ > K+ > Cs+. Ru-based catalysts prepared by the polyol method have good prospects for application in phthalates hydrogenation.

Magnetic Measurements Applied to Energy Storage

AbstractHow to increase energy storage capability is one of the fundamental questions, it requires a deep understanding of the electronic structure, redox processes, and structural evolution of electrode materials. These thorny problems now usually involve spin–orbit, spin‐related electron configuration, etc., which cannot be probed using conventional testing techniques. Considering the intimate connection between spin and magnetic properties, using electron spin as a probe, magnetic measurements make it possible to analyze energy storage processes from the perspective of spin and magnetism. Owing to the capability of characterizing spin properties and high compatibility with the energy storage field, magnetic measurements are proven to be powerful tools for contributing to the progress of energy storage. In this review, several typical applications of magnetic measurements in alkali metal ion batteries research to emphasize the intimate connection between the magnetic properties and electronic structure, which is associated with the electrochemical performance of the electrode materials, are presented. Finally, the current challenges of magnetic measurements and the prospects for enhanced analysis of energy storage systems are discussed.

Bioderived Ionic Liquids with Alkaline Metal Ions for Transient Ionics.

Choline lactate, an ionic liquid composed of bioderived materials, offers an opportunity to develop biodegradable electrochemical devices. Although ionic liquids possess large potential windows, high conductivity, and are nonvolatile, they do not exhibit electrochemical characteristics such as intercalation pseudocapacitance, redox pseudocapacitance, and electrochromism. Herein, bioderived ionic liquids are developed, including metal ions, Li, Na, and Ca, to yield ionic liquid with electrochemical behavior. Differential scanning calorimetry results reveal that the ionic liquids remained in liquid state from 230.42 to 373.15 K. The conductivities of the ionic liquids with metal are lower than those of the pristine ionic liquid, whereas the capacitance change negligibly. A protocol of the Organization for Economic Co-operation and Development 301C modified MITI test (I) confirms that the pristine ionic liquid and ionic liquids with metal are readily biodegradable. Additionally, an ionic gel comprising the ionic liquid and poly(vinyl alcohol) is biodegradable. An electrochromic device is developed using an ionic liquid containing Li ions. The device successfully changes color at -2.5V, demonstrating the intercalation of Li ions into the WO3 crystal. The results suggest that the electrochemically active ionic liquids have potential for the development of environmentally benign devices, sustainable electronics, and bioresorbable/implantable devices.

Design of electrolyte for boosted aqueous battery performance: A critical review and perspective

Aqueous alkali and multivalent metal-ion batteries are practically advantageous for large-scale energy storage because of intrinsic safety and environmental friendliness. Drawbacks, however, include low energy density and short life because of limited electrochemical stability windows (ESWs) of aqueous electrolytes and rapid degradation of electrode materials with high water activity. Despite significant research, including water-in-salt and electrolyte additive(s), directed to the electrolyte to extend ESWs and to boost electrode stability, the practical application remains limited because of the present high cost and generally unsatisfactory performance. Although alkali and multivalent metal ions can have different coordinating structures with solvents and anions, electrolyte design strategies share fundamental mechanisms in either extending ESWs or achieving a passivation layer on the electrode material(s). Future development of aqueous batteries, therefore, is dependent on a systematic understanding and analysis of electrolyte research. Here, we report for the first time a systematic review of the design and engineering of emerging water-based electrolytes for boosted aqueous rechargeable batteries (ARBs) performance. We present a comparative summary of electrochemical stability windows and electrode/electrolyte interphases for five (5) electrolyte types; appraise strategies and the resulting impact of electrolyte properties on electrode interfacial stability; analyze in situ generated electrode/electrolyte interphases; classify advantages and drawbacks of selected strategies; and provide a perspective on future developments in aqueous alkali and multivalent metal-ion batteries, together with methods for the study of both electrolyte and derived interphase(s). We conclude that (1) the design of electrolytes of high concentration and hybrid and eutectic solvents are practically promising for high energy density ARBs; (2) there is a need to improve design for longer cycling life of ARBs; (3) research addresses boosting ESW of the electrolyte; and (4) it increased the understanding of the electrode/electrolyte interface stability via new electrode/electrolyte interphase structures. This review will be of benefit in the practical design of electrolyte(s) for aqueous batteries for high performance and, therefore, of interest to researchers and manufacturers.

Controlling the Redox Catalytic Activity of a Cyclic Selenide Fused to 18-Crown-6 by the Conformational Transition Induced by Coordination to an Alkali Metal Ion.

trans-3,4-Dihydroxyselenolane (DHS), a water-soluble cyclic selenide, exhibits selenoenzyme-like unique redox activities through reversible oxidation to the corresponding selenoxide. Previously, we demonstrated that DHS can be applied as an antioxidant against lipid peroxidation and a radioprotector by means of adequate modifications of the two hydroxy (OH) groups. Herein, we synthesized new DHS derivatives with a crown-ether ring fused to the OH groups (DHS-crown-n (n = 4 to 7), 1-4) and investigated their behaviors of complex formation with various alkali metal salts. According to the X-ray structure analysis, it was found that the two oxygen atoms of DHS change the directions from diaxial to diequatorial by complexation. The similar conformational transition was also observed in solution NMR experiments. The 1H NMR titration in CD3OD further confirmed that DHS-crown-6 (3) forms stable 1:1 complexes with KI, RbCl and CsCl, while it forms a 2:1 complex with KBPh4. The results suggested that the 1:1 complex (3·MX) exchanges the metal ion with metal-free 3 through the formation of the 2:1 complex. The redox catalytic activity of 3 was evaluated using a selenoenzyme model reaction between H2O2 and dithiothreitol. The activity was significantly reduced in the presence of KCl due to the complex formation. Thus, the redox catalytic activity of DHS could be controlled by the conformational transition induced by coordination to an alkali metal ion.

Interfacial configuration and interfacial regulation of electronic properties of MoS2 heterophase junctions

The transition of 1H-transition metal dichalcogenides (TMDCs) to 1H-1T’ heterophase junction can be induced by alkali metal ion intercalation, laser irradiation, electric-field-induced etc, but the interfacial configuration is complex and the effect of the interface on the properties of TMDCs heterophase junction is not well known. Herein, we propose two kinds of interface models, namely, steep interface and gradient interface. The properties of 1H–MoS2 and 1T′-MoS2 phases are well preserved in the steep interface model due to clean atomic interface. In the gradient interface model, the interface configuration is relatively complex, but we find that the defects at the interface can release the local strain to improve the stability of the system. Interestingly, it is found that the 1H-1T’ MoS2 heterophase junction with higher intensity of density of state at the Fermi level (N(EF)) is more stable among the gradient interface model. Finally, it is found that the atoms in the interface of 1H-1T’ MoS2 heterophase junction have the largest out-of-plane deformation due to lattice mismatch regardless of the steep interface model or the gradient interface model, and the key factor affecting the electronic properties of the 1H-1T’ MoS2 heterophase junction is the electronic states of the atoms at the interface. We believe that our research provides a theoretical scheme for the interface regulation to achieve the application of 1H-1T’ heterophase junction based on TMDCs.

Role of Crystal Structure on the Ionic Conduction and Electrical Properties of Germanate Compounds A2Cu3Ge4O12 (A = Na, K)

Crystal structure and electrical properties of A2Cu3Ge4O12 (where A = Na, K) have been investigated by neutron diffraction and electrical impedance spectroscopy (EIS). The real and imaginary parts of the impedance, dielectric constant, and electrical modulus have been studied as a function of frequency and temperature. The crystal structures of the compounds K2Cu3Ge4O12 (KCGO) and Na2Cu3Ge4O12 (NCGO) are made of perfect 2D and quasi-2D alkali metal ion layers, respectively. The dc conductivity occurs due to small polaron hopping for both compounds with single activation energy over the entire experimentally available temperature range. The values of activation energies are 0.90(3) and 1.22(6) eV for KCGO and NCGO, respectively, as determined from dc conductivity and relaxation time analysis. The frequency dependent ac conductivity curves for both compounds follow a universal Jonscher’s power law. Soft bond valence sum analysis of neutron diffraction data reveals that the conduction pathways are confined within a plane in KCGO, whereas they form a one-dimensional channel in NCGO. The bottlenecks for ionic conduction and the role of crystal structure on them are discussed. The scaling behavior of electrical modulus indicates that the relaxation process does not change with temperature; however, a sharp decrease in the time constant has been observed. The present comprehensive study facilitates the understanding of the role of crystal structure on the microscopic mechanism of ionic conduction in both battery materials, which would be useful in designing sodium and potassium based ionic conductors. Further, the constant value of activation energy over the kHz frequency range is suitable for potential applications of the studied materials in avalanche beacons and amateur and geophysical sensors.

From lithium to potassium: Comparison of cations in poly(ethylene oxide)-based block copolymer electrolytes for solid-state alkali metal batteries

Liquid electrolytes (LEs) commonly show severe side reactions at the electrode-electrolyte interface, especially with alkali metal anodes, leading to rapid capacity fade of metal-ion batteries. Solid polymer electrolytes (SPEs), however, contribute to the suppression of side reactions due to their inherent inertness and high mechanical strength, providing long-term stable battery operation. Herein, we investigated physical and electrochemical properties of SPEs based on our previously reported microphase-separated poly(vinyl benzyl methoxy poly(ethylene oxide) ether)-block-polystyrene block copolymer (PVBmPEO-b-PS) with different alkali metal ions (A+ = Li+, Na+ or K+) and their use in the respective metal batteries, showing the potential for the transition from lithium to post-lithium batteries. Rheological and thermal properties as well as ion transport in the SPEs with different bis(trifluoromethanesulfonyl)imide (TFSI) salts concentrations revealed similar shear storage moduli (G’) for the investigated SPEs, while the lowest glass transition temperatures (Tg) were found for KTFSI-based films. By contrast, the highest total ionic conductivity was found for the LiTFSI-based SPEs. To quantify the A+ transference numbers (TA+), the Bruce-Vincent method and pulsed-field gradient (PFG) NMR were conducted, revealing significant challenges for TA+ determination of post-Li systems. Further, the examination of the interfacial stability of SPE/A interfaces by conducting plating/stripping experiments revealed significantly higher resistances for sodium- and potassium-based systems in comparison to their lithium-based counterpart. Nonetheless, A-metal/SPE/cathode cells with PVBmPEO-b-PS-based Na- and K-SPEs with the Prussian Blue analogues (PBAs, Na2-xFe[Fe(CN)6] and K2-xFe[Fe(CN)6]) positive electrodes and the respective alkali metal negative electrodes enabled cycling at elevated temperature of 55 °C. Herein, both sodium and potassium metal batteries exhibited stable cycling with capacity retentions of 73% over 100 cycles for the Na-cell, and 94% over the same cycle number for the K-cell, (and a high coulombic efficiency (CE) of 98% at the 100th cycle).

Revealing alkali metal ions transport mechanism in the atomic channels of Au@α-MnO2

Understanding alkali metal ions' (e.g., Li+/Na+/K+) transport mechanism is challenging but critical to improving the performance of alkali metal batteries. Herein using α-MnO2 nanowires as cathodes, the transport kinetics of Li+/Na+/K+ in the 2 × 2 channels of α-MnO2 with a growth direction of [001] is revealed. We show that ion radius plays a decisive role in determining the ion transport and electrochemistry. Regardless of the ion radii, Li+/Na+/K+ can all go through the 2 × 2 channels of α-MnO2, generating large stress and causing channel merging or opening. However, smaller ions such as Li+ and Na+ cannot only transport along the [001] direction but also migrate along the < 110 > direction to the nanowire surface; for large ion such as K+, diffusion along the < 110 > direction is prohibited. The different ion transport behavior has grand consequences in the electrochemistry of metal oxygen batteries (MOBs). For Li-O2 battery, Li+ transports uniformly to the nanowire surface, forming a uniform layer of oxide; Na+ also transports to the nanowire surface but may be clogged locally due to its larger radius, therefore sporadic pearl-like oxides form on the nanowire surface; K+ cannot transport to the nanowire surface due to its large radius, instead, it breaks the nanowire locally, causing local deposition of potassium oxides. The study provides atomic scale understanding of the alkali metal ion transport mechanism which may be harnessed to improve the performance of MOBs.

Novel Crown Ether Amino Acids as Fluorescent Reporters for Metal Ions.

Unnatural amino acids with enhanced properties, such as increased complexing ability and luminescence, are considered to be highly attractive building blocks for bioinspired frameworks, such as probes for biomolecule dynamics, sensitive fluorescent chemosensors, and peptides for molecular imaging, among others. Therefore, a novel series of highly emissive heterocyclic alanines bearing a benzo[d]oxazolyl unit functionalized with different heterocyclic π-spacers and (aza)crown ether moieties was synthesized. The new compounds were completely characterized using the usual spectroscopic techniques and evaluated as fluorimetric chemosensors in acetonitrile and aqueous mixtures in the presence of various alkaline, alkaline-earth, and transition metal ions. The different crown ether binding moieties as well as the electronic nature of the π-bridge allowed for fine tuning of the sensory properties of these unnatural amino acids towards Pd2+ and Fe3+, as seen by spectrofluorimetric titrations.

Effect of precursor selection on the structure and Li-storage properties of wood-based hard carbon thick electrodes

Herein, balsa wood, poplar wood, and birch wood were selected to systematically study precursors on the structure and Li-storage properties of wood-based hard carbon thick electrodes (WHCTEs). After carbonization, the densities of balsa, poplar, and birch carbon (Bal-W, Pop-W, and Bir-W) reach 99.29, 279.13, and 608.14 mg cm⁻3, respectively. The specific surface areas of Bal-W, Pop-W, and Bir-W are 798, 729, and 609 m2 g⁻1, respectively. Bal-W is rich in mesopores at 2–4 nm; Pop-W also has a certain amount of mesopores; while Bir-W has almost no mesopores but large numbers of micropores concentrated at 1.2 and 1.6 nm. In the battery test, due to the highest mass loading, Bir-W retained the largest remaining capacity among the three samples after 200 cycles at 1 mA cm⁻2. The remaining capacities of Bal-W, Pop-W, and Bir-W are 12.27, 34.15, and 41.03 Ah L⁻1, respectively. It is found that mass loading, specific surface area, and pore size distribution have a greater influence on the electrode capacity performance. In addition, the kinetic features of the Li-ion storage of WHCTEs were studied. This work may provide an important reference for the field of WHCTEs for alkali metal ion batteries and can promote its practical application.

Highly dispersed Pt clusters within ZSM-5 stabilized by alkali metal ions and Al sites for partial methane oxidation

Zeolite is an ideal material to encapsulate nanoparticles and avoid metal aggregation, but it is challenging to achieve a high degree of metal dispersion inside zeolite. In this work, the Na+ reagent was introduced to synthesize Pt@S-1 and Pt@ZSM-5 to explore the effect of Al sites and alkali metal ions on dispersion of Pt nanoparticles. The properties of four catalysts were characterized by XRD, TEM, CO-TPR, TG and FT-IR, and the effects of alkali metal ions were analyzed combined with POM test results. The introduction of a certain amount of alkali metal ions in Pt@ZSM-5 catalyst consumed part of the hydroxyl group to form stable Pt-Ox(OH)yNa active species, which further improves the stability and dispersity of platinum nanoparticles and promotes the activity of partial oxidation of methane. This stabilization strategy can be extended to other porous materials encapsulating metal nanoparticles.