Search

Hypercrosslinked polymers (HCPs), amorphous microporous three-dimensional networks based on covalent linkage of organic building blocks, are a promising class of materials due to their high surface area and easy functionalization; however, this type of material lacks processability due to its network rigidity based on covalent crosslinking. Indeed, the development of strategies to improve its solution processability for broader applications remains challenging. Although HCPs have similar three-dimensionally crosslinked networks to polymer gels, HCPs usually do not form gels but insoluble powders. Herein, we report the synthesis of HCP gels from a thermally induced polymerization of a tetrahedral monomer, which undergoes consecutive solubilization, covalent bond formation, colloidal formation, followed by their aggregation and percolation to yield a hierarchically porous network. The resulting gels feature concentration-dependent hierarchical porosities and mechanical stiffness. Furthermore, these HCP gels can be used as a platform to achieve molecular-level hybridization with a two-dimensional polymer during the HCP gel formation. This method provides functional gels and corresponding aerogels with the enhancement of porosities and mechanical stiffness. Used in column- and membrane-based molecular separation systems, the hybrid gels exhibited a separation of water contaminants with the efficiency of 97.9 and 98.6% for methylene blue and KMnO

Superprotonic phase transition in CsHSO

Designing solid-state electrolytes for proton batteries at moderate temperatures is challenging as most solid-state proton conductors suffer from poor moldability and thermal stability. Crystal–glass transformation of coordination polymers (CPs) and metal–organic frameworks (MOFs) via melt-quenching offers diverse accessibility to unique properties as well as processing abilities. Here, we synthesized a glassy-state CP, [Zn3(H2PO4)6(H2O)3](1,2,3-benzotriazole), that exhibited a low melting temperature (114 °C) and a high anhydrous single-ion proton conductivity (8.0 × 10−3 S cm−1 at 120 °C). Converting crystalline CPs to their glassy-state counterparts via melt-quenching not only initiated an isotropic disordered domain that enhanced H+ dynamics, but also generated an immersive interface that was beneficial for solid electrolyte applications. Finally, we demonstrated the first example of a rechargeable all-solid-state H+ battery utilizing the new glassy-state CP, which exhibited a wide operating-temperature range of 25 to 110 °C., Melt-quenched coordination polymer glass shows exclusive H+ conductivity (8.0 × 10−3 S cm−1 at 120 °C, anhydrous) and optimal mechanical properties (42.8 Pa s at 120 °C), enables the operation of an all-solid-state proton battery from RT to 110 °C.

Developing proton-conducting membranes with three-dimensional conductivity and expedited interfacial contact is requested in the field of fuel cells. Here, we present a design strategy by combining solution processing and material flexibility into amorphous and porous polymers. We design a nanoporous polymer whose skeleton contains dihydrophenazine as a proton-accepting site, and subsequently protonate these sites to produce abundant charges on the polymer skeletons, which enables ionic polymers to be well dispersed in organic solvents and guarantees that they can be fabricated into uniform and amorphous membranes in a solution-processed manner. Importantly, after protonation, the dihydrophenazines change to proton-donating sites, which exhibit dynamic local motions that assist proton exchange on the polymer skeletons and thus construct three-dimensional and unimpeded proton-conduction pathways, with a striking proton conductivity of 0.30 S cm−1 (298 K and 90% relative humidity), a low resistance of 3.02 Ω, and a H+ transport number of 0.98 that was very close to the upper limitation of 1.0.

Reversible solid-to-liquid phase transition in coordination polymer glasses allowed the formation of homogeneous mixed-glasses from two distinct parent compounds. The resulting mixed glasses show composition-dependent glass transition temperatures and unique viscoelastic behaviour. A non-linear mixed glass former effect and controllable anhydrous H

A three-dimensional reduced graphene oxide (3D rGO) sponge with an ultra-high specific pore volume of 6.4 cm3g-1 and oxygen-containing (e.g., carboxyl) groups finely tuned was designed, synthesized, and employed as an ideal host of Li2S6 catholyte and related compounds for high-performance lithium-sulfur batteries (LSBs). To the best of our knowledge, the 3D rGO in this work exhibits the highest specific pore volume ever. The interconnected porous structure of 3D rGO can totally confine the lithium polysulfides overcoming the shuttle effect. Also, it can offer an excellent electrical conductivity and electrolyte transportation leading to high charge storage capacity. The as-fabricated LSB provides a high discharge capacity of 1607 mAh g−1 at 0.1C and a high areal capacity of 3.53 mAh cm−2. Even at a high sulfur loading content of 6.6 mg cm−2, high utilization (79.4%) of active materials at the 0.1C and low capacity fading rate of 0.065% per cycle at the 1.0C with 98% coulombic efficiency over 200 cycles are achieved. The 3D rGO sponge could be useful for high-energy battery applications.

The crystal–liquid–glass phase transition of coordination polymers (CPs) and metal–organic frameworks (MOFs) offers attractive opportunities as a new class of amorphous materials. Unlike conventional glasses, coordination chemistry allows the utilization of rational design concepts to fine-tune the desired properties. Although the glassy state has been rare in CPs/MOFs, it exhibits diverse advantages complementary to their crystalline counterparts, including improved mass transport, optical properties, mechanical properties, and the ability to form grain-boundary-free monoliths. This Review discusses the current achievements in improving the understanding of anomalous phase transitions in CPs/MOFs. We elaborate on the criteria for classifying CP/MOF glasses and comprehensively discuss the three common strategies employed to obtain a glassy state. We include all CP/MOF glass research progress since its inception, discuss the current challenges, and express our perspective on future research directions.

Prussian blue analogues (PBAs), a class of microporous crystalline coordination frameworks, are long known for their diverse properties in porosity, magnetic, charge transport, catalysis, optics, and more. Versatile structural composition and the ability to control defect ordering through synthetic conditions offer opportunities to manipulate the functionality in the crystalline state. However, developments in Prussian blue analogues (PBAs) have primarily revolved around the ordered crystalline state, and the glassy state of PBAs has not yet been explored. Here we report the discovery of a disordered glassy state of the PBA via mechanically induced crystal–glass transformation. We found the preservation of metal–ligand–metal connectivity, confirming the short-range order and semiconductor behaviour, exhibiting an electronic conductivity value of 0.31 mS cm−1 at 50 ˚C. Mechanical-induced glass transformation also triggers changes in electronic states, where electroneutrality is compensated by introducing unconventional CN− vacancies. Partial disorders and ligand vacancies in recrystallized PBA give rise to an enhanced porosity, inaccessible in the crystalline parent. The present work also established a correlation between the mechanical stress required to initiate crystal–glass transformation and intrinsic mechanical properties, which are controlled by the vacancy/defect content, the presence of interstitial water, and the overall composition of PBAs.

Melt and glassy states of coordination polymers (CPs)/metal-organic frameworks (MOFs) have gained attention as a new class of amorphous materials. Many bridging ligands such as azolate, nitrile, thiocyanide, thiolate, pyridine, sulfonate, and amide are available to construct crystals with melting temperatures in the range of 60-593 °C. Here, we discuss the mechanism of crystal melting, glass structures, and mechanical properties by considering both experimental and theoretical studies. High and exclusive H+ or Li+ conductivities in moldable CP glasses have been proven in the all-solid-state devices such as fuel cells or secondary batteries. Transparent glasses with wide composition and available dopants are also attractive for nonlinear optics, photoconductivity, emission, and light-harvesting. The ongoing challenge in the field is to develop the design principles of CP/MOF melts and glasses, corresponding functions of mass (ion, electron, photon, phonon, and so forth). transport and conversion, and the integration of devices with the use of their tunable mechanical properties.

Lithium-sulfur battery (LSB) is considered as a potential candidate for future energy storage device due to its high specific capacity and energy density as well as the natural abundance of sulfur. However, poor capacity retention, polysulfide shuttle effect, and low electronic conductivity have hindered practical uses of the LSB. The introduction of interlayer has been proven to be a promising strategy to improve the overall performance of the LSB. Herein, the influence of various amine-based functional groups of carbon interlayer on lithium polysulfide (LPS) chemisorption was compared via electrochemical methods and density functional theory (DFT) calculations. The functionalized carbon interlayers with 4-aminobenzoic acid, 1,6-diaminohexane, p-phenylenediamine, 4-nitroaniline, and 4-aminothiophenol prepared by an amide coupling reaction show a strong contribution to reduce the polysulfide migration, resulting in the enhancement of overall LSB performances such as a superior capacity and high Coulombic efficiency along with long cyclability of the cells. The LSB with 4-aminobenzoic acid could achieve an initial specific capacity of 1694 mAh g−1 (0.1 C) with an extremely low capacity decay of 0.055% per cycle due to the cooperative interaction of H- and Li-bonds between 4-aminobenzoic acid-functionalized interlayer and polysulfides.

Insight into the influence of hydration energy of structural cations within birnessite-type layered MnO2 on charge storage mechanisms via redox reaction and intercalation/deintercalation processes ...

New insight into the influence of Li+, Na+, and K+ cations between adjacent layers of birnessite-type manganese oxides (MnOx) towards the intercalation/deintercalation charge storage mechanism as a neutral electrochemical capacitor (1 M Na2SO4) is demonstrated. These structural cations play a major role in both the kinetic electron transfer in a faradaic redox reaction and the accessibility of the compensating electrolyte ions. Li-MnOx shows the highest Mn utilization of 51% followed by Na-MnOx (40%) and K-MnOx (31%), respectively.

Hydrazine is a common reducing agent widely used in many industrial and chemical applications; however, its high toxicity causes severe human diseases even at low concentrations. To detect traces of hydrazine released into the environment, a robust sensor with high sensitivity and accuracy is required. An electrochemical sensor is favored for hydrazine detection owing to its ability to detect a small amount of hydrazine without derivatization. Here, we have investigated the electrocatalytic activity of layered birnessite manganese oxides (MnO

Even though Li-ion based energy storages can provide high specific energy and good cycling stability, the scarcity and high price of Li-based materials may limit their applications in the future. In this work, we have investigated Na-ion hybrid capacitors (NICs) with both high specific energy and power. Bio-derived or Jasmine rice-derived hierarchical porous carbon (j-HPC) with a specific BET surface area of 2377 m2 g−1 and a mean pore diameter of 2.53 nm containing 73.17 at.% C, 2.24 at.% N, and 24.59 at.% O is used as a new electrode of NICs. We have found that a fast Na ion diffusion of 10−8-10−11 cm2 s−1 and a fast-standard heterogeneous rate constant of electron transfer of ca. 10−5 cm s−1 are two reasons leading to high-performance NIC. The NIC exhibits a maximum operating cell voltage of 3.8 V, a maximum specific energy of 116 Wh kg−1 (142 μWh cm−2) and a maximum specific power of 11,121 W kg−1 (13,618 μW cm−2) with 90% capacity retention after 5000 cycles. Our NIC using j-HPC may be an ideal device for high power and energy storage technology.

Even though the electrochemical capacitors could exhibit an impressive specific power as compared to other energy storage systems, their specific energies still limit their superiority in term of battery replacement. Apart from conventional method to improve the specific energy via complex electrode development, here an alternative route to enhance the performance of the N-doped graphene oxide aerogel supercapacitor using a redox active electrolyte was introduced. The effect of ferrocene methanol in 1-butyl-1-methylpyrrolidinium dicyanamide ionic liquid electrolyte as a redox active electrolyte was investigated. The coupling of this new hybrid electrolyte and a unique nanostructure of the N-doped reduced graphene oxide aerogel could exhibit an excellent specific capacitance and specific energy of 112.1 F g-1 and 34.2 Wh kg-1, respectively as compared to 76.7 F g-1 and 23.5 Wh kg-1 of the conventional 1-butyl-1-methylpyrrolidinium dicyanamide ionic liquid electrolyte. These significant improvements are attributed to the enablement of the Faradaic charge transfer contribution within the redox active electrolyte itself. This redox electrolyte could be used in any high-energy supercapacitors.

Sluggish kinetics of oxygen reduction reaction (ORR) are the critical challenge for metal-air batteries and fuel cells. To increase the reaction rate, the high-efficient electrocatalysts are needed. Among various catalysts, platinum and its alloys are investigated as the best catalyst for the ORR. However, the use of Pt-based catalysts is still suffered from many disadvantages including excessive cost, scarcity, and poor stability. In this work, lithium-birnessite (Li-bir), reduced graphene oxide (rGO), and Li-bir/rGO nanocomposite were tested as the ORR catalysts. The linear sweep voltammogram (LSV) curves at a scan rate of 10 mV s-1 show that the Li-bir/rGO nanocomposite provides the best catalytic performance with an onset potential of 0.87 V vs. RHE, half-wave potential of 0.72 V vs. RHE, limiting current density of 5.72 mA٠cm-1 (at a rotation rate of 1600 rpm), along with the Tafel slope of 92.5 mV٠dec-1. Furthermore, the electron transfer number per oxygen molecule calculated by Koutechy–Levich (K–L) equation is 3.84, indicating a 4-electron pathway for the ORR suggesting that the Li-bir/rGO nanocomposite can be used as a high-efficient ORR catalyst. More interestingly, a current retention of the Li-bir/rGO nanocomposite remains over 84 % while the current density of the commercial Pt/C decreases to 67 % after 17,000 seconds. The catalyst in this work may be practically used in many applications such as metal-air batteries.

Although electrochemical double layer capacitors (EDLCs) have high specific power, their specific energy is rather low. To address this issue, a composite material between EDLC-type N-doped graphene aerogel (N-rGOae) with an N-doped content of ca. 8 at% and pseudocapacitor-type mixed-valence manganese oxide (MnOx) nanoparticles with a diameter of

Understanding the sensing reaction mechanism at the solid electrode-liquid electrolyte interface during the detection is crucial for developing chemical sensors. In this work, layered MnO2 nanosheets were coated on nitrogen-doped reduced graphene oxide aerogel (3D-N-rGO) rotating disk electrode (RDE) and used towards hydrazine detection. The successive reduction in the oxidation number of Mn in the MnO2/3D-N-rGO electrode during the detection monitored by an in situ electrochemical X-ray absorption spectroscopy (XAS) indicates that 0.15 mol electrons produced from the oxidation of hydrazine do transfer to MnO2. The hydrodynamic diffusion of hydrazine from bulk solution to the surface of the MnO2/3D-N-rGO RDE investigated also plays a major role in the sensitivity of hydrazine detection. The limit of detection (LOD) value at a signal-to-noise ratio of ca. 3 is 085.0 μM (4000 rpm) with a response time of l -arginine. In addition, the MnO2/3D N-rGO RDE sensor can practically be used to detect trace hydrazine in real-world samples i.e., drinking water and lake water.

The effect of the intercalated alkaline cations between the adjacent layers of multilayered manganese oxide (MnOx) towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was investigated. Li–MnOx, Na–MnOx, K–MnOx, Rb–MnOx, and Cs–MnOx provide OER overpotentials of 1.64, 1.70, 1.79, 1.83, and 1.84 V vs. RHE, respectively as well as ORR overpotentials of 0.71, 1.06, 1.13, 1.15, and 1.14 V vs. RHE, respectively. Li–MnOx shows the highest bifunctional catalytic activity towards both the ORR and OER. In addition, the Gibbs free energy change of *OH adsorption is found to be the largest throughout the reaction pathways determining the rate of the whole ORR and OER.

The unusual intercalation phenomena of alkali cations (Li+, Na+, K+, Rb+, and Cs+) in the sulfate-based electrolyte on the electrochemical behavior of birnessite-type layered-manganese oxide nanosheets with Li-intercalated cation (Li-MnO2) were studied by in situ electrochemical synchrotron X-ray Absorption spectroscopy. Li-MnO2 exhibits the highest charge storage capacity in Na2SO4(aq), followed by Li2SO4, K2SO4, and Cs2SO4, respectively. Whilst, it does not exhibit the charge-storage characteristics in Rb2SO4 as the solvated Rb+ could not intercalate into the lamellar structure of birnessite. Understanding unusual intercalation phenomena can be useful for further development of the electrochemical capacitors.

The sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a crucial issue that limits a practical utilization of metal-air batteries. Manganese oxides with various structures, δ-, β-, α-, or γ-MnO2, have been studied and reported as electrocatalysts for the ORR and/or OER. Here, we have suggested birnessite-typed layered manganese oxides (δ-MnO2) with their sheet-like structure and interlayer spacing of ca. 7 Å containing different alkaline intercalated cations within the layers as bifunctional electrocatalysts. Surprisingly, the experimental results together with a fundamental explanation by density functional theory (DFT) calculations show that the intercalated cations between layers of the birnessite (Bir) play an important role on the ORR and OER catalytic activities which have the activity trend as follow: Li-Bir > Na-Bir > K-Bir > Rb-Bir > Cs-Bir.[1] Apart from the fundamental study, primary Zn-air batteries with these materials are also demonstrated. Zn-air battery with the Li-Bir catalyst shows the highest performance among these catalysts. Moreover, we also integrated the Li-Bir with reduced graphene oxide (rGO) as a composite to improve the electronic conductivity of the MnO2. The mechanical rechargeable Zn-air battery with Li-Bir/rGO composite as an air electrode demonstrates better performances than the Zn-air battery with a pristine Li-Bir catalyst. Interestingly, even the Zn-air battery with the Li-Bir/rGO composite (0.687 V) shows higher potential gap between discharge and charge potentials than state-of-art Pt/C+RuO2 (0.667 V) in the first cycle (2 hours per cycle), however, the Zn-air with our composite catalyst exhibits smaller potential gaps of 0.697 V and 0.719 V (0.720 and 0.761 V for Pt/C+RuO2) at the second and third cycles, respectively. In addition, our mechanical rechargeable Zn-air battery displays an impressive cyclability of discharge-charge processes (10 minutes per cycle) of 500 cycles or over 83 hours at a current density of 2 mA cm-2. Therefore, the Li-bir/rGO composite could be used as a bifunctional electrocatalyst in a practical application for Zn-air batteries. Reference [1] S. Kosasang, N. Ma, P. Wuamprakhon, N. Phattharasupakun, T. Maihom, J. Limtrakul, M. Sawangphruk, Chem. Commun. 2018, 54, 8575.

Lithium-sulfur battery (LSB) is a promising candidate as a conventional lithium-ion battery replacement due to its high theoretical specific capacity and high energy density together with additional advantages of low cost, abundance, and environment friendliness. However, LSB still suffers from many issues including natural insulator of active sulfur and final product of Li2S, polysulfide shuttle effect, and 80% volume expansion during cycling which are causes of capacity fading in the LSB. To fix the mentioned issues as well as improve performances of LSB, carbon interlayer has introduced between a sulfur cathode and separator to suppress lithium polysulfide diffusion and act as an upper current collector. Here, we prepare surface modified carbon fiber paper (CFP) via a simple amide coupling reaction with various amine reactants to study the effect of functional groups on the surface of the CFP on LSB performances. LSB with modified CFPs as interlayers show significant higher specific capacity than LSB without interlayer due to the chemisorption ability between functional groups on the CFP surfaces and lithium polysulfide intermediates. The LSB with modified CFP by 4-aminobenzoic acid interlayer exhibits the highest specific capacity along with long cyclability observed from high capacity retention of 88.5% and Coulombic efficiency above 98% after 200 cycles. Furthermore, the lithium polysulfide chemisorption capabilities of each functional group are fundamentally explained via density functional theory (DFT) calculations through the binding energy between functional groups and polysulfide intermediates. More interestingly, we also prove that the excellent performance of the LSB with 4-aminobenzoic acid interlayer is due to the strong lithium bond of S-L…O coupled with hydrogen bond of S…H-O.

The sluggish kinetics of oxygen reduction reaction (ORR) is a critical challenge for metal-air batteries and fuel cells. To increase the reaction rate, the high-efficient electrocatalysts are needed. Among various catalysts, platinum and its alloys are investigated as the best catalyst for the ORR. However, the Pt-based catalysts suffer from many disadvantages, including excessive cost, scarcity, and poor stability. In this work, layered manganese oxides, Li-birnessite, Na-birnessite, K-birnessite and their composites with graphene aerogel were used as the ORR catalysts. The ORR catalytic activity of these materials has been studied using rotating disk electrode (RDE) in O2-saturated and Ar-saturated KOH solution. The linear sweep voltammogram (LSV) curves at scan rate of 10 mVs- 1 show that the Li-birnessite/graphene aerogel provided the best catalytic performance with an onset potential of 0.99 V (V vs. RHE), half wave potential of 0.66 V (V vs. RHE), limiting current density of 5.60 mA cm- 1 (at a rotation rate of 1600 rpm), and Tafel slope of 104.3 mV dec- 1, which is comparable to the Pt catalyst. Moreover, the electron transfer number per oxygen molecule (n) calculated by Koutechy–Levich (K–L) equation is ~ 4, indicating a 4-electron pathway for ORR and suggesting the Li-birnessite manganese oxide coated on graphene aerogel as a high-efficient ORR catalyst.

We propose a new concept of using a redox additive potassium ferrocyanide in 1-butyl-1-methylpyrrolidinium dicyanamide ionic liquid electrolyte for high-performance supercapacitors. Coupling with a unique nanostructure of N-doped reduced graphene oxide, the supercapacitor using this new hybrid electrolyte exhibits the excellent specific energy and power of 89 Wh kg-1 and 3677 W kg-1, respectively. An excellent long-term stability is demonstrated up to 10000 cycles of charge-discharge with 87% capacitance retention.