Diffusion Pathways Research Articles

Multiple inter-tillage weeding effect on methane and nitrous oxide emissions pathways from rice paddy fields in Hokkaido, Japan

ABSTRACT Rice paddy fields are important sources of methane (CH4) and nitrous oxide (N2O). Generally, CH4 is emitted predominantly via rice, with smaller contributions from ebullition and diffusion, while CH4 oxidation varies by pathway. Research on N2O emissions remains ongoing. Multiple inter-tillage weeding (MIW), a traditional Japanese practice, is believed to enhance rice yield and improve anaerobic soil conditions. However, its effects on CH4 and N2O emission pathways remain unclear. This study aimed to quantify MIW’s impact on CH4 and N2O emissions through three pathways and MIW-mediated. Diffusive gas flux was determined by extracting net gas flux based on threshold values. Ebullitive gas flux was measured using a bubble-trapping method. Rice-mediated gas flux was calculated as the difference between total gas flux and the sum of diffusive and ebullitive gas fluxes. A chamber with disturbance functionality was developed to measure the MIW-mediated gas flux. Treatments of 0 (T0), 2 (T2), and 5 (T5) MIW practices were compared with conventional rice farming as a reference. Analysis of CH4 and N2O emission pathways during the MIW period revealed that gaseous CH4 influenced the ebullition and rice-mediated pathways, increasing the relative contribution of the diffusion pathway. High-frequency MIW (T5) enhanced the release of CH4-rich bubbles, temporarily reducing rice-mediated CH4 emissions. However, the contributed rate of MIW-mediated CH4 emission to the total CH4 emission during cultivation period were low. High-frequency MIW (T5) promoted N2O production in soil and paddy field water, but the emission rate exceeded its formation and consumption rates, potentially increasing atmospheric-soil concentration gradients and enhancing N2O absorption via the rice pathway. At medium frequency (T2), N2O emissions during the MIW period were similar to those under no MIW (T0). MIW-mediated N2O emissions accounted for 4–5% of the total cultivation period emissions at T2 and about 30% at T5, highlighting MIW-mediated N2O emissions playing a secondary role under high-frequency MIW. During the cultivation period, CH4 emissions were 72–86% via rice, 13–27% via diffusion, and 1–2% via ebullition. N2O was slightly emitted via diffusion and ebullition, whereas absorption was observed in rice.

Endplate Remodeling: a key indicator of cigarette smoke exposure-induced intervertebral disc degeneration in a male rat model

Abstract Recent clinical studies have established a strong association between cigarette smoking and degenerative disc disease. Both in vitro and in vivo research indicated that cigarette smoke disrupts cellular homeostasis in the intervertebral disc (IVD), leading to spatiotemporal remodeling of the extracellular matrix, with a notable reduction in solute diffusivity within the cartilage endplate (CEP). As the CEP serves as a critical mechanical barrier and solute diffusion pathway for the IVD, both roles can be compromised by pathological changes in the tissue. This underscores the need for a more comprehensive examination of endplate remodeling during IVD degeneration, particularly in the context of cigarette smoking and cessation. The objective of this study was to perform a quantitative analysis of the structure-material property relationship changes in the endplate at tissue and cellular levels to determine how endplate mineralization progresses during IVD degeneration in the context of cigarette smoke exposure and cessation, using our previously developed Sprague–Dawley rat model. Our results indicates that cigarette smoke exposure induced endplate remodeling is characterized by a higher CEP histological grade, increased aberrant CEP calcification level, and elevated bony endplate surface flatness score, all of which correlated with an accelerated chondrocyte cell life cycle. Smoke cessation alone was insufficient to reverse the mineralization progression in the endplate. Principal component analysis further identified alterations in endplate morphometry at the tissue level and disruptions in the chondrocyte life cycle at cellular level as key markers of degenerative remodeling. These findings establish endplate remodeling as a key indicator of smoke exposure induced IVD degeneration and inform the development of novel therapeutic strategies aimed at preserving or improving disc health.

Interaction between Hydrogen and Magnesium Films: From Hydrogenochromism to Applications.

Hydrogen, as a promising clean energy carrier, underscores the critical need for reliable detection technologies to ensure its safe and efficient use. Magnesium (Mg) thin films, with their hydrogenochromic properties, are particularly well-suited for hydrogen sensing applications due to their dramatic optical transitions. However, practical implementation faces challenges in achieving both rapid response and durability under cyclic conditions. To overcome these limitations, advanced interfacial tuning techniques have been developed to optimize hydrogen diffusion pathways and reinforce structural resilience. This review focuses on the scientific mechanism governing the interaction between Mg-based thin films and hydrogen, highlighting their suitability as hydrogen sensors with superior hydrogenochromic characteristics. Controllable manufacturing methods allow precise control over the alloy composition and microstructure of Mg-based thin films, facilitating the construction of phases and interfaces conducive to support efficient hydride formation, ultimately improving hydrogen response performance. Recent advancements in microstructure engineering, refined in situ characterization techniques, and promising optical applications drive the rapid development of Mg-based thin films.

Stable hexaazatrinaphthylene-based covalent organic framework as high-capacity electrodes for aqueous hybrid supercapacitors

Covalent organic frameworks (COFs) have great potential as electrodes for aqueous hybrid supercapacitors (AHCs) owing to their designable structure and resourceful advantages. However, their low capacities and high structure instability in aqueous electrolytes limit the onward practical applications. Here, we have synthesized robust hexaazatrinaphthylene-based COF (HATN-COF) by a simple condensation between cyclohexanehexone and 2,3,6,7,10,11-hexaiminotriphenylene. The π-conjugation skeleton, porous structure, and high-proportioned imine bonds give HATN-COF sufficient electron and ion diffusion pathways for rapid reaction kinetics together with abundant exposed active sites for large capacity. Meanwhile, the formed hydrogen bond networks by ethanol molecules in frameworks improve the acid-base tolerance. As a consequence, HATN-COF delivers an exceptional specific capacity of 367 mAhg-1 at 1 A g-1 (maximum value among reported COF-related electrodes in AHCs), high rate capability with 259.7 mAhg-1 at 20 A g-1, and superior cycle durability with retaining 97.8% of its capacity even after 20,000 cycles. Moreover, the AHC, constructed by HATN-COF as the positive electrode and activated carbon as the negative electrode, exhibits a large energy density of 67 Wh kg-1 at a power density of 375 W kg-1, accompanied by outstanding cycling stability. The research presents a promising approach for designing high-performance COF electrodes for advanced AHCs.

Revisiting the in-plane and in-channel diffusion of lithium ions in a solid-state electrolyte at room temperature through neural network-assisted molecular dynamics simulations.

Developing superionic conductor (SIC) materials offers a promising pathway to achieving high ionic conductivity in solid-state electrolytes (SSEs). The Li10GeP2S12 (LGPS) family has received significant attention due to its remarkable ionic conductivity among various SIC materials. Ab initio molecular dynamics (AIMD) simulations have been extensively used to explore the diffusion behavior of Li+ ions in Li10GeP2S12. These simulations indicate that Li+ ions diffuse rapidly along a one-dimensional (1D) chain direction, specifically along the c-axis, a process known as in-channel diffusion. In addition, these computational studies have identified additional diffusion pathways within the ab planes, referred to as in-plane diffusion. However, there are still notable limitations in the time scale associated with AIMD simulation techniques for studying the dynamic behavior of Li10GeP2S12 at room temperature. In this study, we trained a deep potential (DP) model for the LGPS system and performed a 300-nanosecond DeePMD simulation to investigate the diffusion behavior of Li10GeP2S12 at room temperature. The neural network (NN) assisted simulation showed that the framework structure of LGPS remained remarkably stable over the entire 300-nanosecond period. Following this, our investigation focused on the two-dimensional (2D) diffusion pathways within the ab plane (in-plane diffusion mechanism) and the 1D diffusion channel along the c-axis (in-channel diffusion mechanism). Upon analyzing the DeePMD simulation results, we identified two distinct pathways for in-plane Li+ diffusion within the ab plane: the Li-2 and Li-4 pathways. We determined the energy barriers for the two diffusion pathways to be 0.23 eV and 0.34 eV, respectively, in qualitative agreement with recent experimental and theoretical results. For the in-channel diffusion along the c-axis, our calculated energy barrier was approximately 0.083 eV, closely matching the previous one-particle potential (OPP) analysis. Our results confirm experimental and theoretical studies, indicating that lithium ions experience significantly less resistance when diffusing through the in-channel pathway compared to the in-plane migration mechanism. However, our findings suggest that despite having a higher energy barrier than the Li-4 pathway, the Li-2 pathway remains a viable option for in-plane lithium-ion migration.

Heterointerface Built Up by Ultrathin Amorphous MoO3 Conformal Coating Enables V5O12·6H2O with Superior Properties for Aqueous Zinc Batteries.

Layered V5O12·6H2O is a promising candidate for aqueous zinc batteries (AZBs) but with moderate electrochemical performances. Herein, the charge storage properties of V5O12·6H2O are markedly improved by building up the heterointerface on its surface using amorphous molybdenum trioxide as the heteromaterial. The amorphous molybdenum trioxide functioning as the proton reservoir enables the proton-involved electrochemical reactions and induces the formation of a built-in electric field along the [001] orientation at the heterointerface constructed by the (001) plane of V5O12·6H2O, which could provide new diffusion pathways and extra sites for ion storage. As a result, V5O12·6H2O with significantly improved kinetics realizes an ultrahigh capacity of 510 mAh g-1, better rate capability, and prolonged lifespan. This work provides general guidance for designing advanced cathode materials for AZBs with respect to heterostructure.

AA-Stacked Hydrogen-Substituted Graphdiyne for Enhanced Lithium Storage.

Graphdiyne (GDY) has been considered a promising electrode materialfor application in electrochemical energy storage. However, studies on GDY featuring an ordered interlayer stacking are lacking, which is supposed to be another effective way to increase lithium binding sites and diffusion pathways. Herein, we synthesized a hydrogen-substituted GDY (HsGDY) with a highly-ordered AA-stacking structurevia a facile alcohol-thermal method. Such unique architecture enables a rapid lithium transfer through the well-organized pore channels and endows a stronger adsorption capability to lithium atom as compared to the arbitrarily-stacked mode. The resultant HsGDY exhibits a reversible capacity of 1040 mA h g-1 at 0.05 A g-1ranking among the most powerful GDY-based electrode materials, and an excellent rate performanceas well as a long-term cycling stability. The successful preparationof gram-level high-quality HsGDY products in batches implies thepotential for large-scale lithium-storage applications.

Understanding the influence of hydrogen on BCC iron grain boundaries using the kinetic activation relaxation technique (k-ART)

Abstract Hydrogen embrittlement (HE) poses a significant challenge to the mechanical integrity of iron and its alloys. This study explores the influence of hydrogen atoms on two distinct grain boundaries (GBs), $\Sigma37$ and $\Sigma3$, in body-centered-cubic (BCC) iron. Using the kinetic activation relaxation technique (k-ART), an off-lattice kinetic Monte Carlo approach with an EAM-based potential, extensive catalogs of activated events for atoms in both H-free and H-saturated GBs were generated.
Studying the diffusion of H, we find that, for these systems, while GB is energetically favorable for H, this element diffuses more slowly at the GBs than in the bulk. The results further indicate that the $\Sigma 3$ GB exhibits higher stability in its pure form compared to the $\Sigma 37$ GB, with notable differences in energy barriers and diffusion behaviors. Moreover, with detailed information about the evolution landscape around the GB, we find that the saturation of a GB with hydrogen both stabilizes the GB by shifting barriers associated with Fe diffusion to higher energies and reducing the number of diffusion events. For the $\Sigma 37$ GB, the presence of hydrogen causes elastic deformation, affecting the diffusion of Fe atoms both at the GB and in adjacent positions. This results in new diffusion pathways but with higher diffusion barriers, unlike for the $\Sigma 3$ GB. These results indicate that the presence of hydrogen rigidifies the direct GB interface layers while allowing more atoms to be active for the $\Sigma 37$ GB. This provides a microscopic basis to support the existence of competing mechanisms compatible with either plasticity (such as hydrogen enhanced localized plasticity --- HELP) or energy-dominated (hydrogen enhanced decohesion mechanism ---HEDE) embrittlement, with the relative importance of these mechanisms determined by the local geometry of the GBs.

Dehydrogenase versus oxidase function: the interplay between substrate binding and flavin microenvironment.

Redox enzymes, mostly equipped with metal or organic cofactors, can vary their reactivity with oxygen by orders of magnitudes. Understanding how oxygen reactivity is controlled by the protein milieu remains an open issue with broad implications for mechanistic enzymology and enzyme design. Here, we address this problem by focusing on a widespread group of flavoenzymes that oxidize phenolic compounds derived from microbial lignin degradation, using either oxygen or a cytochrome c as electron acceptors. A comprehensive phylogenetic analysis revealed conserved amino acid motifs in their flavin-binding site. Using a combination of kinetics, mutagenesis, structural, and computational methods, we examined the role of these residues. Our results demonstrate that subtle and localized changes in the flavin environment can drastically impact on oxygen reactivity. These effects are afforded through the creation or blockade of pathways for oxygen diffusion. Substrate binding plays a crucial role by potentially obstructing oxygen access to the flavin, thus influencing the enzyme's reactivity. The switch between oxidase and dehydrogenase functionalities is thereby achieved through targeted, site-specific amino acid replacements that finely tune the microenvironment around the flavin. Our findings explain how very similar enzymes can exhibit distinct functional properties, operating as oxidases or dehydrogenases. They further provide valuable insights for the rational design and engineering of enzymes with tailored functions.

Unraveling the conversion mechanism toward spinel sulfides as cathode materials for Mg-ion batteries.

Rechargeable Mg batteries are promising candidates for achieving considerable high-energy-density. Enhancing the energy density can be achieved by integrating metallic Mg anodes with conversion-type cathode materials, which are characterized by multi-electron transfer process and elevated specific capacities in contrast to intercalation-type materials. Despite these advantages, the conversion-type cathodes still have some challenges of substantial volume expansion, sluggish diffusion kinetics and intricate mesophase evolution during repeated electrochemical reactions. Herein, first-principles calculations were performed to probe into the electronic properties, Mg2+ dynamical properties, Bader charge and electrochemical mechanism of spinel-type sulfides (M3S4, M = Co and Ni). The band gap values of Co3S4 and Ni3S4 are 0.28 and 0 eV, respectively, showing their superior electrical conductivity. The preferential order of Mg intercalation sites is 16c > 48f > 8b. Computational predictions of the formation energy and discharge voltage indicate that spinel Ni3S4 can exhibit a relatively high specific discharge capacity of 220.8 mA h g-1 and an average voltage of ∼1.6 V vs. Mg2+/Mg with an energy density of 353.3 W h kg-1 at a Mg intercalation concentration of x2+Mg = 1.25, surpassing those of Co3S4 and Mo6S8. According to the principle of the lowest barrier, the diffusion pathway "oct → tet → oct" of spinel sulfides Co3S4 and Ni3S4 has low Mg migration barrier values of 1.10 and 0.67 eV, respectively. The Bader charge and AIMD results revealed that the spinel M3S4 (M = Co and Ni) underwent conversion reactions to the rock-salt phase especially at deep discharge. These insights significantly advance the rational design of spinel sulfides with a conversion reaction mechanism, providing great potential for the development of Mg batteries with high energy density.

Enhanced piezo-phototronic effect in carbon nitride nanosheets via oxidative exfoliation for high-efficiency piezo-photocatalysis

The obtained E500-CN serves dual functions in piezo-photocatalysis by providing effective piezoelectric responses and reduced charge carrier recombination, benefiting from the shortened diffusion pathway and the synergistic piezo-phototronic effect.

Topotactic phase transformation of lithiated spinel to layered LiMn0.5Ni0.5O2: the interaction of 3-D and 2-D Li-ion diffusion

Newly discovered cubic Li-excess spinel (LxS) structured LiMn0.5Ni0.5O2 cathode shows unique temperature-dependent topotactic phase transformation between 400–900 °C, affecting Li ion diffusion pathways and electrochemical performance.

Open frameworks in the NaxMny(P2O7)mFn fluoro-pyrophosphates system.

Three new sodium manganese fluoro-pyrophosphate compounds, namely, Na5.5Mn1.5(P2O7)2F0.5 (I), Na7Mn0.75(P2O7)2F2 (II), and Na9Mn3(P2O7)4F (III), have been synthesized by heating a mixture of NaPF6, Na2PO3F or NaH2PO4 with different Mn sources in NaNO3 and KNO3 fluxes. The structures of the title compounds were characterized via single-crystal X-ray diffraction (XRD). II is characteristic of a shell of Na+ ions that encloses one [Mn0.75(P2O7)2F2]7- unit, whereas I and III reveal three-dimensional (3D) frameworks that consist of MnO6, Mn/NaO5F0.5 octahedra or MnO6 octahedra and distorted MnO5 square pyramids with P2O7 units, where Na+ cations reside in different-membered ring one-dimensional (1D) tunnels. The estimated total Na+ ion conductivity for a pellet of III in open air is 10-5 S cm-1 at 400 °C, which is lower than that of many NASICON-type compounds at room temperature, with a higher activation energy of 0.89 eV for III compared to the value of ∼0.4 eV for high-performance sodium ion conductors. The analysis of Na+ diffusion pathways revealed that percolation occurs through a zig-zag chain along the b axis via the bond valence energy landscape approach. Detailed characterization, such as spectroscopic and magnetic properties and specific heat for III, is also reported.

Buckled-layer K1.39Mn3O6: a novel cathode for potassium-ion batteries.

A novel buckled-layer K1.39Mn3O6 cathode was synthesized, featuring P2-oxygen stacking and P3-K sites. The presence of two independent manganese sites significantly influences the charge distribution and diffusion pathways of potassium ions during the charge and discharge processes, resulting in exceptional electrochemical performance. A reversible capacity of 105 mA h g-1 at 100 mA g-1 and remarkable rate capability of 70 mA h g-1 at 1 A g-1 were achieved, surpassing those of most previously reported layered transition metal oxide cathodes. The findings facilitate the development of innovative cathode materials.

Effects of porous hedgehog-like morphology and graphene oxide on the cycling stability and rate performance of Co3O4/NiO microspheres.

A porous hedgehog-like Co3O4/NiO/graphene oxide (denoted as PHCNO/GO) microsphere was prepared by a facile solvothermal method, followed by an annealing treatment under argon atmosphere. Benefiting from the thin Co3O4/NiO nanosheets with a large specific surface area, abundant pores distributed between the Co3O4/NiO nanosheets, and GO firmly wrapped around the surface of PHCNO microspheres, the PHCNO/GO microspheres showed excellent lithium storage performance. The Co3O4/NiO nanosheets provided numerous active sites, achieving a high reversible specific capacity. The pores distributed between the Co3O4/NiO nanosheets created numerous diffusion pathways for lithium ions and relieved stress from the charging/discharging process. Meanwhile, GO supported the PHCNO microspheres, enhancing their cycling stability. A high reversible specific capacity of 383.9 mA h g-1 was maintained after 1000 cycles at 3000 mA g-1. In addition, GO improved the conductivity of PHCNO microspheres and then achieved a good rate performance; a high reversible specific capacity of 526.7 mA h g-1 was obtained at 5000 mA g-1. This work provided a reference for synthesizing high-performance lithium-ion battery anode materials.

An Adaptable Structure of Metal‐Organic Framework Glass Interlayer Enables Superior Performance in Aqueous Zinc‐Ion Batteries

AbstractThe practical application of safe and cost‐effective aqueous zinc‐ion batteries is enhanced by the metal‐organic frameworks (MOFs), which possess tunable porous structures and chemical compositions that can facilitate the desolvation and transport of Zn2+ ions at the anode interface. However, ensuring the structural stability and operational life of crystalline MOFs in batteries remains a challenge. Here, a breakthrough is presented in tackling this dilemma. A MOF glass interlayer, specifically the ZIF‐62 glass interlayer, is designed and fabricated for the Zn anode. The integration of this interlayer endows the Zn anode with a remarkable cyclic lifespan. It also achieves outstanding cyclability in Zn||MnO2 full‐cell with limited Zn excess, showing no capacity decay after 600 cycles at 0.5 A g−1, and in a Zn||iodine pouch battery with a mass loading of 12.85 mg cm−2. This superior cyclicity is attributed to the ease of distortion of Zn[ligand]4 tetrahedra and the reduced likelihood of disconnection between adjacent tetrahedra within the glass interlayer, as compared to its crystalline counterpart. The unique structure of ZIF‐62 glass provides an increased degree of configurational freedom, allowing it to withstand mechanical stress and extend the Zn2+ ion diffusion pathway. This ensures high cycling stability and rapid interfacial diffusion kinetics.

Electrified Enhanced Recovery of Lithium from Unconventional Sources.

Demand for lithium is expected to quadruple by the end of the decade. Without new sources of production, the supply-demand curve is expected to invert. Traditional geological reserves will not be able to meet the anticipated gap, thus unconventional sources of lithium will need to be utilized, setting the stage for fierce competition for perhaps the most critical of mineral resources required for the energy transition. Direct Lithium Extraction refers to the umbrella of technologies being developed to access lithium from unconventional sources. Electrochemical extraction offers significant promise for its selectivity and low operating cost when coupled with renewable energy. This review aims to describe materials and process design considerations for electrochemical extraction of lithium from aqueous sources with a specific emphasis on ζ-V2O5 designed in our research group as an insertion host. We point to specific strategies for improving capacity and selectivity for electrochemical lithium extraction based on materials design across length scales. Strategies range from site-selective modification of insertion hosts to controlled tortuosity of ion diffusion pathways in porous electrode architectures. Electrochemical lithium extraction from unconventional sources stands poised to be a linchpin of a sustainable economy when coupled with cleaning of wastewater, hydrogen generation, and recovery of ancillary critical metals.

Interfacial Reactivity-Triggered Oscillatory Lattice Strains of Nanoalloys.

Understanding the structure evolution of nanoalloys under reaction conditions is vital to the design of active and durable catalysts. Herein, we report an operando measurement of the dynamic lattice strains of dual-noble-metal alloyed with an earth-abundant metal as a model electrocatalyst in a working proton-exchange membrane fuel cell using synchrotron high-energy X-ray diffraction coupled with pair distribution function analysis. The results reveal an interfacial reaction-triggered oscillatory lattice strain in the alloy nanoparticles upon surface dealloying. Analysis of the lattice strains with an apparent oscillatory irregularity in terms of frequency and amplitude using time-frequency domain transformation and theoretical calculation reveals its origin from a metal atom vacancy diffusion pathway to facilitate realloying upon dealloying. This process, coupled with surface metal partial oxidation, constitutes a key factor for the nanoalloy's durability under the electrocatalytic oxygen reduction reaction condition, which serves as a new guiding principle for engineering durable or self-healable electrocatalysts for sustainable fuel cell energy conversion.

Visualization and quantification of Li distribution in garnet solid electrolytes Li6.25La3Zr2Al0.25O12

Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for all-solid-state batteries due to its structural stability and high Li+ ionic conductivity, but high-purity LLZO crystallizes in a low-conductivity tetragonal phase at room temperature (RT). Al doping stabilizes the cubic structure, yet its impact on Li+ migration is not fully understood. Using Li6.25La3Zr2Al0.25O12 (LLZAO) as a model, we conducted temperature-dependent neutron powder diffraction (NPD), neutron pair distribution function (nPDF), and density-functional theory (DFT) computations. NPD results, supported by nPDF, show Li+ ions at 24d and 96h sites, excluding 48g. Al at 24d adjusts the distribution of Li, improving ionic conductivity near RT. Maximum Entropy Method analyses indicate a temperature-driven 3D Li diffusion pathway of 24d-96h-96h-24d channels, confirmed by DFT. This work will enhance the understanding of Li diffusion and the optimization of ionic conductivity in garnet-type solid electrolytes.

Combined Displacement/Intercalation Mechanism of Ag0.33V2O5 Cathode for Rechargeable Zinc‐Ion Batteries

Zinc‐ion batteries are gaining recognition as viable options for energy storage systems due to their air stability, abundance, affordability, and ease of use. However, existing zinc‐storage materials primarily consist of intercalation cathode materials, necessitating the development of host structures with enhanced performance. Herein, the use of silver vanadate, Ag0.33V2O5, as a cathode material is explored and its detailed displacement/intercalation mechanism is elucidated, encompassing silver, proton, and zinc‐ion storage behaviors. Electrochemical behavior, structural analysis, and diffusion barrier calculation techniques are used to delineate cation diffusion pathways. Additionally, 3D electron density mapping is performed to visualize the cation reaction mechanism. The proposed material demonstrates an impressive reversible capacity of about 303 mAh g−1 at a current of 0.1 A g−1, along with outstanding cycle retention stability even at high current densities.