Low Energy Barrier Research Articles

‘Invisible’ Molecular Dynamics Revealed for a Conformationally Chiral π‐Stacked Perylene Bisimide Foldamer

Whilst energetic and kinetic aspects of folding processes are meanwhile well understood for natural biomacromolecules, the folding dynamics in so far studied artificial foldamer counterparts remain largely unexplored. This is due to the low energy barriers between their conformational isomers that make the dynamic processes undetectable with conventional methods such as UV/vis absorption, fluorescence, and NMR spectroscopy, making such processes ‘invisible’. Here we present an asymmetric perylene bisimide dimer (bis‐PBI 1) that possesses conformational chirality in its folded state. Owing to the large interconversion barrier (≥ 116 kJ mol–1), four stereoisomers could be separated and isolated. Since the interconversion between these stereoisomers requires the foldamer to first open and then to re‐fold, the transformation of one stereoisomer into others allowed us to ‘visualize’ the dynamics of folding with time and determine its lifetimes and the energetic barriers associated with the folding process. Supported by quantum chemical calculations, we identified the open structure to be only a fleeting metastable state of higher energy. Our experimental observation of the kinetics associated with the molecular dynamics in the PBI foldamer advances the fundamental understanding of folding in synthetic foldamers and paves the way for the design of smart functional materials.

'Invisible' Molecular Dynamics Revealed for a Conformationally Chiral π-Stacked Perylene Bisimide Foldamer.

Whilst energetic and kinetic aspects of folding processes are meanwhile well understood for natural biomacromolecules, the folding dynamics in so far studied artificial foldamer counterparts remain largely unexplored. This is due to the low energy barriers between their conformational isomers that make the dynamic processes undetectable with conventional methods such as UV/vis absorption, fluorescence, and NMR spectroscopy, making such processes 'invisible'. Here we present an asymmetric perylene bisimide dimer (bis-PBI 1) that possesses conformational chirality in its folded state. Owing to the large interconversion barrier (≥ 116 kJ mol-1), four stereoisomers could be separated and isolated. Since the interconversion between these stereoisomers requires the foldamer to first open and then to re-fold, the transformation of one stereoisomer into others allowed us to 'visualize' the dynamics of folding with time and determine its lifetimes and the energetic barriers associated with the folding process. Supported by quantum chemical calculations, we identified the open structure to be only a fleeting metastable state of higher energy. Our experimental observation of the kinetics associated with the molecular dynamics in the PBI foldamer advances the fundamental understanding of folding in synthetic foldamers and paves the way for the design of smart functional materials.

In Situ Unraveling Surface Reconstruction of Ni‐CoP Nanowire for Excellent Alkaline Water Electrolysis

The surface reconstruction behavior of transition metal phosphides precursors is considered as an important method to prepare efficient oxygen evolution catalysts, but there are still significant challenges in guiding catalyst design at the atomic scale. Here, the CoP nanowire with excellent water splitting performance and stability is used as a catalytic model to study the reconstruction process. Obvious double redox signals and valence evolution behavior of the Co site are observed, corresponding to Co2+/Co3+ and Co3+/Co4+ caused by auto‐oxidation process. Importantly, the in situ Raman spectrum exhibits the vibration signal of Co–OH in the non‐Faradaic potential interval for oxygen evolution reaction, which is considered the initial step in reconstruction process. Density functional theory and ab initio molecular dynamics are used to elucidate this process at the atomic scale: First, OH− exhibits a lower adsorption energy barrier and proton desorption energy barrier at the configuration surface, which proposes the formation of a single oxygen (–O) group. Under a higher –O group coverage, the Co–P bond is destroyed along with the POx groups. Subsequently, lower P vacancy formation energy confirm that the Ni‐CoP configuration can fast transform into a highly active phase. Based on the optimized reconstruction behavior and rate‐limiting barrier, the Ni‐CoP nanowire exhibit an excellent overpotential of 1.59 V at 10 mA cm−2 for overall water splitting, which demonstrates low degradation (2.62%) during the 100 mA cm−2 for 100 h. This work provide systematic insights into the atomic‐level reconstruction mechanism of transition metal phosphides, which benefit further design of water splitting catalysts.

AB–stacked bilayer β12–borophene as a promising anode material for alkali metal-ion batteries

As the lightest 2D material, monolayer borophene exhibits a specific charge capacity of 1860 mA h g−1 for Li-ion batteries, which is four times higher than that of graphite and is one of the highest specific charge capacities ever reported for 2D anode materials. Additionally, it showed high mechanical strength and a low diffusion barrier. However, monolayer borophene suffers from stability issues in its free-standing form, which restricts its real-life applications. Inspired by the recent experimental investigations, which proved the higher stability of bilayer borophene polymorphs (BBPs) over their monolayer counterparts, in this work, we investigated the dynamical and thermodynamical stabilities of both AA– and AB–stacked BBPs in their β12 phase using first-principles calculations. Between the two stacking patterns, we found that only the AB–stacked β12–BBP is both energetically and dynamically stable, and we further investigated its potential as a high-performance anode material for alkali metal-ion batteries. Our investigations show that AB–stacked β12–BBP exhibits good electrical conductivity before and after metal atom (Li/Na/K) adsorption onto it. Further, AB–stacked β12–BBP adsorbs the metal atoms strongly with adsorption energies ranging between −0.89 to −1.44 eV, indicating that there is a lesser possibility of forming dendrites on this anode. Similarly, it has a low diffusion energy barrier (~ 0.13–0.49 eV) for metal atoms, meeting the fast charge/discharge rate requirements. Moreover, it exhibits a reasonably low average metal-insertion voltage (0.43 to 0.65 V) and a specific charge capacity of 330–413 mA h g−1 that is comparable to graphite. All the above findings suggest that the AB–stacked bilayer β12– borophene can be a potentially favorable anode material.

Reversible Local Protonation-Deprotonation: Tuning Stimuli-Responsive Circularly Polarized Luminescence in Chiral Hybrid Zinc Halides for Anti-Counterfeiting and Encryption.

Precise control over the organic composition is crucial for tailoring the distinctive structures and properties of hybrid metal halides. However, this approach is seldom utilized to develop materials that exhibit stimuli-responsive circularly polarized luminescence (CPL). Herein, we present the synthesis and characterization of enantiomeric hybrid zinc bromides: biprotonated ((R/S)-C12H16N2)ZnBr4 ((R/S-LH2)ZnBr4) and monoprotonated ((R/S)-C12H15N2)2ZnBr4 ((R/S-LH1)2ZnBr4), derived from the chiral organic amine (R/S)-2,3,4,9-Tetrahydro-1H-carbazol-3-amine ((R/S)-C12H14N2). These compounds showcase luminescent properties; the zero-dimensional biprotonated form emits green light at 505 nm, while the monoprotonated form, with a pseudo-layered structure, displays red luminescence at 599 and 649 nm. Remarkably, the reversible local protonation-deprotonation behavior of the organic cations allows for exposure to polar solvents and heating to induce reversible structural and luminescent transformations between the two forms. Theoretical calculations reveal that the lower energy barrier associated with the deprotonation process within the pyrrole ring is responsible for the local protonation-deprotonation behavior observed. These enantiomorphic hybrid zinc bromides also exhibit switchable circular dichroism (CD) and CPL properties. Furthermore, their chloride counterparts were successfully obtained by adjusting the halogen ions. Importantly, the unique stimuli-responsive CPL characteristics position these hybrid zinc halides as promising candidates for applications in information storage, anti-counterfeiting, and information encryption.

Reversible Local Protonation‐Deprotonation: Tuning Stimuli‐Responsive Circularly Polarized Luminescence in Chiral Hybrid Zinc Halides for Anti‐Counterfeiting and Encryption

AbstractPrecise control over the organic composition is crucial for tailoring the distinctive structures and properties of hybrid metal halides. However, this approach is seldom utilized to develop materials that exhibit stimuli‐responsive circularly polarized luminescence (CPL). Herein, we present the synthesis and characterization of enantiomeric hybrid zinc bromides: biprotonated ((R/S)‐C12H16N2)ZnBr4 ((R/S‐LH2)ZnBr4) and monoprotonated ((R/S)‐C12H15N2)2ZnBr4 ((R/S‐LH1)2ZnBr4), derived from the chiral organic amine (R/S)‐2,3,4,9‐Tetrahydro‐1H‐carbazol‐3‐amine ((R/S)‐C12H14N2). These compounds showcase luminescent properties; the zero‐dimensional biprotonated form emits green light at 505 nm, while the monoprotonated form, with a pseudo‐layered structure, displays red luminescence at 599 and 649 nm. Remarkably, the reversible local protonation‐deprotonation behavior of the organic cations allows for exposure to polar solvents and heating to induce reversible structural and luminescent transformations between the two forms. Theoretical calculations reveal that the lower energy barrier associated with the deprotonation process within the pyrrole ring is responsible for the local protonation‐deprotonation behavior observed. These enantiomorphic hybrid zinc bromides also exhibit switchable circular dichroism (CD) and CPL properties. Furthermore, their chloride counterparts were successfully obtained by adjusting the halogen ions. Importantly, the unique stimuli‐responsive CPL characteristics position these hybrid zinc halides as promising candidates for applications in information storage, anti‐counterfeiting, and information encryption.

Synergistic Vertical Graphene‐Exsolved Perovskite to Boost Reaction Kinetics for Flexible Zinc–Air Batteries

AbstractZinc–air batteries (ZABs) hold significant promise for flexible electronics due to their high energy density and low cost. However, their practical application is hindered by the sluggish kinetics of the oxygen evolution and oxygen reduction reactions (OER/ORR). This study highlights a novel design of vertical graphene arrays (VGs) anchored on PrBa0.5Sr0.5Co1.8Ru0.2O5+δ (PBSCRu) perovskite nanofibers, fabricated via plasma‐enhanced chemical vapor deposition. Notably, the VG growth induces the exsolution of Co nanoparticles from the PBSCRu perovskite, resulting in a unique PBSCRu‐Co‐VG heterostructure. Theoretical calculations demonstrate that constructing PBSCRu‐Co‐VG heterojunction regulates interfacial electronic redistribution, thereby lowering energy barriers for both OER and ORR. As a result, the PBSCRu@VG‐5 electrocatalyst exhibits superior stability and higher peak power density in both liquid and flexible solid‐state ZABs compared to the pristine PBSCRu electrocatalyst. This protocol advances the integration of synergetic perovskite/metal/graphene composites, offering considerable potential for next‐generation energy conversion technologies.

Exploring the factors influencing the ketoenamine-enolimine tautomeric equilibrium of pyridoxal 5′-phosphate in branched-chain aminotransferases

Pyridoxal 5′-phosphate (PLP), the active form of vitamin B6, is a critical coenzyme for various enzymes. It generates a Schiff base with the substrate and exhibits ketoenamine and enolimine tautomeric forms due to intramolecular proton transfer. This study aims to ascertain the predominant tautomeric form of the PLP Schiff base in MtIlvE and analyze its influencing factors. Molecular dynamics simulations indicate that the ketoenamine tautomer has higher binding free energy than the enolimine tautomer. Density functional theory calculations suggest that, despite their ability to interconvert at a relatively low energy barrier, the ketoenamine tautomer is thermodynamically more stable. Factors affecting the keto-enol tautomeric equilibrium were investigated by constructing various QM-cluster models. Our results demonstrate that both the protonation of the pyridine nitrogen and the presence of Tyr209, which stabilizes the O3 anion, shift the tautomeric equilibrium toward the ketoenamine configuration. These findings provide a theoretical basis for investigating enzyme catalytic mechanisms.

Meso/Microporous Single‐Atom Catalysts with Curved Fe‐N4 sites Boost the Oxygen Reduction Reaction Activity

Zeolitic‐imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe‐N/C materials, which are promising catalysts for enhancing the performance of Zn‐air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF‐derived Fe‐N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe‐N/C material with curved Fe‐N4 active sites, denoted as FeSA‐N/TC, through the pyrolysis of hemin‐modified ZIF films on ZnO nanorods, obtained from the self‐assembly reaction between Zn2+ from ZnO hydrolysis and 2‐methylimidazole. Density functional theory calculations demonstrate that the curved Fe‐N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA‐N/TC exhibits exceptional ORR performance with half‐wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA‐N/TC achieves high peak power densities (H2‐O2 PEMFC: 1100 mW cm–2; H2‐Air PEMFC: 715 mW cm–2; liquid‐state ZAB: 228 mW cm–2; solid‐state ZAB: 112 mW cm–2), demonstrating its feasibility and efficiency in practical applications.

Meso/Microporous Single-Atom Catalysts with Curved Fe-N4 sites Boost the Oxygen Reduction Reaction Activity.

Zeolitic-imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe-N/C materials, which are promising catalysts for enhancing the performance of Zn-air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF-derived Fe-N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe-N/C material with curved Fe-N4 active sites, denoted as FeSA-N/TC, through the pyrolysis of hemin-modified ZIF films on ZnO nanorods, obtained from the self-assembly reaction between Zn2+ from ZnO hydrolysis and 2-methylimidazole. Density functional theory calculations demonstrate that the curved Fe-N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA-N/TC exhibits exceptional ORR performance with half-wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA-N/TC achieves high peak power densities (H2-O2 PEMFC: 1100 mW cm-2; H2-Air PEMFC: 715 mW cm-2; liquid-state ZAB: 228 mW cm-2; solid-state ZAB: 112 mW cm-2), demonstrating its feasibility and efficiency in practical applications.

A Multifunctional NaxBi/NaCl Flexible Interface Layer for Solid‐State Na Metal Batteries

AbstractNa3Zr2Si2PO12 (NZSP) electrolyte with excellent air stability and acceptable ionic conductivity demonstrates a significant potential for application in solid‐state Na metal batteries. However, the poor interfacial contact between NZSP and Na anode has severely hindered its practical application. Herein, a BiCl3/polytetrafluoroethylene flexible interface layer is constructed between NZSP and Na metal anode. BiCl3 can react with Na metal to form a multifunctional NaxBi/NaCl‐rich flexible interface layer during the cycling process, which can effectively enhance the interfacial contact, avoid the formation of voids and reduce the interfacial resistance. NaxBi with low energy barrier can provide fast Na+ diffusion path, and NaCl with a wide band gap can inhibit electron injection and suppress Na dendrite growth. Owing to the multifunctional NaxBi/NaCl flexible interface layer, the Na/BiCl3@NZSP/Na symmetric cell exhibits a reduced interfacial resistance from 1252.1 to 67.6 Ω and achieves a high critical current density of 2 mA cm⁻2 at 25 °C. At 0.1 mA cm⁻2/0.1 mAh cm⁻2 and 0.3 mA cm⁻2/0.3 mAh cm⁻2, the symmetric cell can stably cycle for 3000 and 1100 h. Additionally, the Na3V2(PO4)3/BiCl3@NZSP/Na full cell can retain 96.7% of initial capacity (≈111 mAh g−1) after 300 cycles at 0.5 C and excellent rate capability.

Large out-of-plane piezoelectric response and ultra-low polarization transition barriers in two-dimensional MoGe2N4/MoSi2N4 heterostructures

With the help of the first principle calculations, two-dimensional (2D) MoGe2N4/MoSi2N4 van der Waals (vdW) heterojunction was confirmed as a type II bandgap arrangement with distinct piezoelectric properties dependent on the stacking orders and interlayer interactions. This structural change is facilitated by slip interactions between the layers and is characterized by a process with a low energy barrier, allowing for efficient and responsive phase transition of structures. Notably, this heterojunction exhibits a particularly large out-of-plane piezoelectric coefficient, d33, within a finite thickness. Concurrently, the piezoelectric coefficient can be enhanced by adjusting the vertical strain to a specific value, and the out-of-plane piezoelectric coefficient d33 can be as high as 73.28 pm/V, which is larger than the values of the available 2D materials or their heterojunctions. In addition, we simulated a piezoelectric actuator on a two-dimensional scale, where the deformation of the upper surface of the piezoelectric brake was linearly modulated by adjusting the driving voltage. Thus, our research paves the way for the conceptualization and creation of cutting-edge nanoelectronic devices, electromechanical systems, and multifunctional atomic-scale appliances.

Every reaction Detail Matters: An in silico driven Step-by-Step Guide to understand the B2O3-Catalyzed CO2 to cyclic carbonates conversion

The catalytic conversion of carbon dioxide (CO2) to cyclic organic carbonates (COCs) via cycloaddition with epoxides offers a dual benefit of reducing CO2 emissions while producing valuable chemical products. In this detailed in silico study, we employ density functional theory (DFT) to meticulously investigate the mechanisms underlying the B2O3/n-NBu4Br-catalyzed cycloaddition of CO2 and epoxides, following a step-by-step approach according to the reaction details. We provide a comprehensive comparison of the non-catalyzed, n-NBu4Br alone, and B2O3/n-NBu4Br-catalyzed pathways, emphasizing two distinct active sites within the B2O3 framework: Site 1 (six-membered boroxol ring) and Site 2 (open chain configuration). Our computational analysis highlights that the Site 1-catalyzed reaction pathway is more favorable, featuring a lower overall energy barrier of 26.8 kcal/mol, compared to 32.5 kcal/mol for the Site 2-catalyzed pathway. Detailed intrinsic bond orbital (IBO), natural adaptive orbital (NAdO) and distortion-interaction analysis (DIA) reveal significant differences in bonding properties and energy interactions, elucidating why Site 1 exhibits superior catalytic activity over Site 2. These findings are corroborated by experimental observations, which indicate that ball milling B2O3 increases defect sites, thereby enhancing exposure of active sites Site 1 and improving catalytic performance. This study provides an in-depth understanding of how the intrinsic properties of boron active sites influence the catalytic efficiency of B2O3, offering valuable insights for the design and optimization of metal-free catalysts for CO2 conversion.

FeNiCu-based composite catalyst for hydrogen storage in MgH2

FeNiCu-based composite catalysis proves to be an effective strategy for enhancing the hydrogen storage performance of MgH2. Two catalysts, (Cu0.2Ni0.8) O/NiFe2O4 and FeNi3/Fe4Cu3, are successfully synthesized and doped into MgH2 to improve its hydrogen storage capability. Experimental results demonstrate that MgH2 + 5 wt% (Cu0.2Ni0.8)O/NiFe2O4 (MgH2 + 5 A) and MgH2 + 5 wt% FeNi3/Fe4Cu3 (MgH2 + 5B) composites desorption at 171 ℃ and 178 ℃, respectively, which is 100 ℃ lower than that of ball-milled MgH2. Under conditions of 150 ℃ and 3 MPa, MgH2 + 5 A can absorb 6.02 wt% H2 in just one minute. MgH2 + 5B, at 225/325 ℃, exhibits hydrogen absorption/desorption exceeding 7 wt% H2 for 1 h. The synergistic effect of in situ formed Mg2Ni and Fe positively impacts the hydrogen storage behavior of MgH2. The introduced interface offers numerous low-energy barrier H-diffusion channels, resulting in accelerated release and hydrogen absorption. Additionally, Cu4O3 dispersed on the surface of the matrix particles maintains its valence during the process of hydrogen absorption/desorption. This property can facilitate the conversion of Mg2Ni/Mg2NiH4 into a “hydrogen pump”. This study provides an experimental basis and new insights for designing highly efficient catalysts for Mg-based hydrogen storage materials.

Latent Electronic (Anti-)Ferroelectricity in BiNiO_{3}.

BiNiO_{3} exhibits an unusual metal-insulator transition from Pnma to P1[over ¯] that is related to charge ordering at the Bi sites, which is intriguingly distinct from the charge ordering at Ni sites usually observed in related rare-earth nickelates. Here, using first principles calculations, we first rationalize the phase transition from Pnma to P1[over ¯], revealing an overlooked intermediate P2_{1}/m bridging phase and a complex interplay between distinct degrees of freedom. Going further, we point out that the charge ordering at Bi sites in the P1[over ¯] phase is not unique. We highlight an alternative polar ordering giving rise to a ferroelectric Pmn2_{1} phase nearly degenerated in energy with P1[over ¯] and showing an in-plane electric polarization of 53 μC/cm^{2} directly resulting from the charge ordering. The close energy of Pmn2_{1} and P1[over ¯] phases, together with low energy barrier between them, make BiNiO_{3} a potential electronic antiferroelectric in which the field-induced transition from nonpolar to polar would relate to nonadiabatic intersite electron transfer. We also demonstrate the possibility to stabilize an electronic ferroelectric ground state from strain engineering in thin films, using an appropriate substrate.

Highly-Branched PtCu Nanocrystals with Low-Coordination for Enhanced Oxygen Reduction Catalysis.

Low-coordination platinum-based nanocrystals emanate great potential for catalyzing the oxygen reduction reactions (ORR) in fuel cells, but are not widely applied owing to poor structural stability. Here, several PtCu nanocrystals (PtCu NCs) with low coordination numbers were prepared via a facile one-step method, while the desirable catalyst structures were easily obtained by adjusting the reaction parameters. Wherein, the Pt1Cu1 NCs catalyst with abundant twin boundaries and high-index facets displays 15.25 times mass activity (1.647 A mgPt -1 at 0.9 VRHE) of Pt/C owing to the abundant effective active sites, low-coordination numbers and appropriate compressive strain. More importantly, the core-shell and highly developed dendritic structures in Pt1Cu1 NCs catalyst give it an extremely high stability with only 17.2% attenuation of mass activity while 61.1% for Pt/C after the durability tests (30 000 cycles). In H2-O2 fuel cells, Pt1Cu1 NCs cathode also exhibits a higher peak power density and a longer-term lifetime than Pt/C cathode. Moreover, theoretical calculations imply that the weaker adsorption of intermediate products and the lower formation energy barrier of OOH* in Pt1Cu1 NCs collaboratively boost the ORR process. This work offers a morphology tuning approach to prepare and stabilize the low-coordination platinum-based nanocrystals for efficient and stable ORR.

Ultrafast antiferromagnetic switching of Mn2Au with laser-induced optical torques

Ultrafast manipulation of the Néel vector in metallic antiferromagnets most commonly occurs by generation of spin-orbit (SOT) or spin-transfer (STT) torques. Here, we predict another possibility for antiferromagnetic domain switching by using novel laser optical torques (LOTs). We present results of atomistic spin dynamics simulations from the application of LOTs for all-optical switching of the Néel vector in the antiferromagnet Mn2Au. The driving mechanism takes advantage of the sizeable exchange enhancement, characteristic of antiferromagnetic dynamics, allowing for picosecond 90 and 180-degree precessional toggle switching of the Néel vector with laser fluences on the order of mJ/cm2. A special symmetry of these novel torques greatly minimises the over-shooting effect common to precessional spin switching by SOT and STT methods. We demonstrate the opportunity for LOTs to produce deterministic, non-toggle switching of single antiferromagnetic domains. Lastly, we show that even with sizeable ultrafast heating by laser in metallic systems, there exist a large interval of laser parameters where the LOT-assisted toggle and preferential switchings in magnetic grains have probabilities close to one. The proposed protocol could be used on its own for all-optical control of antiferromagnets for computing or memory storage, or in combination with other switching methods to lower energy barriers and/or to prevent over-shooting of the Néel vector.

Synthesis, Reaction Mechanism, DNA Cleavage, and Antitumor Properties of Pyridazinedione‐Fused Enediynes

AbstractNatural enediyne antibiotics undergo thermally induced cycloaromatization under physiological conditions to generate highly reactive diradicals that effectively abstract hydrogen atoms from biomacromolecules like DNA, leading to DNA cleavage and inducing programmed cell death in tumor cells, exhibiting potent cytotoxicity and broad‐spectrum antitumor properties. In order to further explore promising synthetic analogues of natural enediynes, a 3,6‐pyridazinedione moiety was fused at the ene‐position, and 10 new enediyne compounds with different atoms at the propargylic positions were synthesized. Differential scanning calorimetry (DSC) and electron paramagnetic resonance results indicated that these enediynes exhibited a rather low onset temperature and the capability to generate radical species at physiological temperatures. Density functional theory (DFT) calculations demonstrated that the pyridazinedione moiety facilitates cascade rearrangement processes, thereby endowing the key cycloaromatization with a low energy barrier. The enediynes with propargylic oxygen exhibit strong DNA cleavage capabilities, and all pyridazinedione‐fused enediynes showed IC50 values in the range of several tens of micromolars against HeLa cells.

Increment entropy promoted small-polaron breakdown in metal–organic frameworks for sodium-ion batteries

Metal-organic frameworks (MOFs) show great promise for sodium-ion batteries owing to diverse structures, versatile functionalities, controllable chemical compositions/surface chemistry, adjustable host–guest interactions, and custom-designed pore structure, however, struggling with inferior rate capability because of the polaronic effect induced slow electron transfer. Herein, a polaron breakdown strategy was proposed to enhance the electron transport in MOF (Ni2+ and 2,3,6,7,10,11-hexaaminotriphenylene hexahydrochloride based MOF, NOF). Specifically, the increment entropy strategy was adopted by inserting another metal ion (Cu2+, Co2+, Mn2+) into the crystal lattice of NOF (IE-NOF) to break down the symmetry of 2-dimensional layer and elicited polaron breakdown to rescue the electrons from the self-trapped condition, acquiring fast electron transfer. The electrical conductivity of the as-synthesized IE-NOF-Mn/Co/Cu/Ni (1:1:1:1) is 30 times higher than the pristine NOF. DFT calculation exhibits that IE-NOF-Mn/Co/Cu/Ni (1:1:1:1) breaks down small-polaron to generate highly delocalized electrons and reduce the mutual interaction of Na-N to facilitate the Na+ diffusion, contributing lower energy barrier compared to NOF (0.1 vs 0.5 eV). The anode of IE-NOF-Mn/Co/Cu/Ni (1:1:1:1) shows a high capacity of 551 mAh g−1 at 100 mA g−1, and a high-rate property of 303.1 mAh g−1 at 5 A g−1. The strategy of increment entropy to promote polaron breakdown to enhance charge transfer is conducive to fast-charging battery development.

Co/CoTe heterostructure internal hairy fibers as high-efficiency oxygen electrocatalyst for Zn-air batteries

The design of highly efficient catalysts to enhance the kinetics of oxygen reduction (OER) and oxygen evolution (ORR) reactions is the key issue for the development of high-performance Zn-air battery. In this work, we report the design of Co-CoTe heterostructured fibers as the bifunctional oxygen catalyst for Zn-air battery. Firstly, the theoretical analysis was carried out on Co-CoTe heterostructure. The large work function difference is favorable to construct strong interfacial built-in electric field (BIEF), and the low energy barrier endows high catalytic activities. Moreover, the in-situ grown carbon shell was designed to build “core–shell” Co-CoTe/C unit to realize its high performance. They assemble the Co-CoTe@HFS fiber with good self-supporting and flexible features. Taken the advantages of the strong BIEF, the “core–shell” basic unit, and the freestanding substrate, the Co-CoTe@HFS fiber achieves the good electrocatalytic properties and high reliability. The full Zn-air battery (ZAB) with the Co/CoTe@HFS air cathode achieves the high peak power density and cycling stability over long-term cycling. Therefore, this work provides a clue to design bifunctional oxygen catalysts for high-performance ZABs.