Developing lightweight microwave absorbers with strong attenuation and favorable impedance matching remains challenging. Herein, a composition and temperature-regulated strategy is developed to fabricate one-dimensional (1D) binary magnetic bimetal@carbon (C)@nitrogen doped carbon nanofibers (CNFs) through the electrospinning of Prussian blue analogue@phenolic resin@polyacrylonitrile precursors followed by thermal conversion. The spatial confinement of precursor particles within PAN-derived nanofibers effectively preserves the continuous fibrous framework and restricts the aggregation of alloy nanoparticles, thereby generating abundant magnetic bimetal/C/CNFs heterogeneous interfaces. Carbonization temperature and precursor loading are used to regulate the graphitization degree, dielectric response, attenuation capability, and impedance matching characteristics. Among the samples, the designed CoFe@C@CNFs exhibits the optimum electromagnetic wave absorption performance with a minimum reflection loss of −57.52 dB and an EAB of 5.20 GHz at 1.92 mm. CST simulations further confirms the effective radar cross-section reduction of the CoFe@C@CNFs. Moreover, the approach is extendable to CoNi and FeNi alloy systems. This work provides a versatile route for constructing composition-tunable 1D binary magnetic bimetal@C@CNFs for electromagnetic wave absorption applications.
The advancement of Fe-based oxygen evolution reaction (OER) catalysts lags behind their Ni-based counterparts, albeit their good theoretically predicted performance and low cost. Deeply understanding the catalytic mechanism would be necessary to advance the Fe-based catalysts. Currently, Fe-based non-metallic compounds, such as sulfides, phosphides, and selenides, have been widely explored as highly active OER precatalysts because of their tunable electronic structures and relatively high electrical conductivity. Nevertheless, these precatalysts usually undergo surface reconstruction into oxyhydroxides under OER conditions, making the real active phase different from the pristine compound and complicating the structure-performance relationship. Herein, taking the Ni-doped FeS2 nanosphere catalyst as a platform, we discover a nuanced bidirectional electronic effect within the surface-reconstructed active phase, showcasing the vital roles of both residual FeS2 and Ni dopants in optimizing catalytic performance. Structural characterizations confirm the successful incorporation of Ni dopants into the pyrite FeS2 lattice. An amorphous carbon layer is coated on the sulphide nanospheres, which contributes to improving charge transfer efficiency and maintaining structural integrity during electrocatalysis. As a result, the obtained catalyst, typically denoted as Ni0.2-FeS2@C, achieves markedly enhanced OER activity in the alkaline electrolyte, requiring an overpotential of only 270 mV to reach 10 mA cm−2, much lower than those of the undoped and uncoated counterparts (FeS2@C and FeS2). Moreover, Ni0.2-FeS2@C exhibits negligible activity decay after 5000 cyclic voltammetry cycles and remains stable during 100 h of constant-potential operation, with Faradaic efficiency for oxygen production close to 100%, demonstrating good catalytic durability and selectivity. Spectroscopic analyses and density functional theory calculations reveal that surface reconstruction during OER leads to the formation of oxyhydroxide as reported elsewhere, but unique electronic interactions, which have not been observed earlier. On the one hand, the residual FeS2 substrate upshifts the d-band center of the surface oxyhydroxide, strengthening the adsorption behavior of the crucial oxygenated intermediate. On the other hand, Ni dopants induce a downshift of the d-band center, which weakens over-binding inversely. The resulting bidirectional modulation optimizes the electronic structure of active sites and effectively balances the adsorption strength of OER intermediates, thereby reducing the OER energy barrier. Consequently, this work not only provides a viable strategy for the rational design of Fe-based OER catalysts but also deepens the mechanistic understanding of the real active phase of balanced electronic modulation in enhancing electrocatalytic activity.
Lithium-ion batteries (LIBs) underpin modern portable electronics, electric transportation, and grid-scale energy storage, yet thermal runaway (TR) remains a critical safety barrier under the increasing demand for higher energy density. A major challenge in understanding TR is that its early-stage reactions are highly coupled: salt decomposition, solvent degradation, gas generation, interfacial reconstruction, and heat release typically occur simultaneously within a narrow temperature window. This complexity makes it difficult to identify which cell components initiate or accelerate thermal failure. In existing TR models, the copper current collector is generally regarded as an electrically conductive but chemically inert substrate. However, this assumption has rarely been experimentally verified under realistic thermal-abuse conditions, mainly because the chemical contribution of copper is easily masked by the intense reactions of lithiated anodes and electrolytes. Clarifying whether copper is merely a passive structural component or an active participant is therefore essential for improving the mechanistic accuracy of battery safety models. Here, we overturn the conventional view of copper as an inert current collector and demonstrate that it plays an active dual-function role-as both a catalyst and a reactant-in the early thermal failure of LIBs. By combining multi-scale thermal analysis, operando gas chromatography–mass spectrometry (GC-MS), and surface-sensitive spectroscopies, we show that copper surfaces markedly accelerate the conversion of LiPF6 to PF5. This process occurs at temperatures as low as 180 °C, nearly 100 °C earlier than in copper-free systems. This finding is significant because PF5 is a highly reactive Lewis acid that can prematurely trigger electrolyte decomposition before the temperature reaches the conventionally recognized severe thermal-abuse regime. The prematurely generated PF5 further initiates a catalytic cascade that promotes ring-opening decarboxylation of cyclic carbonate solvents, especially ethylene carbonate (EC) and fluoroethylene carbonate (FEC). Consequently, copper-containing systems exhibit substantially increased release of reductive gases, including CH4 and C2H4, together with enhanced CO2 evolution. Surface analysis further reveals the formation of fluorinated products on copper, confirming that copper is not only catalytically involved but also chemically consumed during electrolyte decomposition. The destabilizing effect of copper becomes more pronounced in the lithiated graphite anode–electrolyte system, where it increases the total heat release by 53.6%. These findings indicate that neglecting the chemical contribution of copper may lead to a systematic overestimation of the thermal stability of LIBs. By identifying copper–electrolyte interaction as a previously missing link in the TR chain, this work provides a mechanistic foundation for revising battery safety prediction models and opens a new materials-design direction for intrinsically safer current collectors.
Metal-organic frameworks (MOFs) are mostly and intrinsically insulating and typically exhibit weak microwave absorption capacity. Moreover, their frameworks tend to collapse during pyrolysis, which severely limits their stability of the structure and performance in broadband microwave absorption. Meanwhile, the synergistic mechanism between resistance loss and magnetic loss in non-pyrolyzed conductive MOFs remains insufficiently understood at the electronic level. To address these challenges, three-dimensional (3D) conductive Fe-THBQ with an electrical conductivity of 9.17 × 10−5 S cm−1 was rationally synthesized. Density functional theory (DFT) calculations were employed to elucidate the transmission path of interfacial carriers at the electronic structure level, revealing that carrier transfer is primarily concentrated at the Fe-O bonds of Fe-THBQ and clarifying the microscopic origin of the intrinsic dielectric response in 3D conductive Fe-THBQ. On this basis, flake-like Co3O4@Co was introduced into the non-pyrolyzed Fe-THBQ to construct Fe-THBQ/Co3O4@Co composites, enabling effective magnetoelectric coupling between magnetic loss and resistance loss. The as-prepared Fe-THBQ/Co3O4@Co composites exhibit an effective absorption bandwidth (EAB) of 5.6 GHz at a thickness of 2.0 mm and a minimum reflection loss (RLmin) of −42.65 dB at 2.4 mm. Microwave absorption mechanism demonstrates that the flake-like and magnetic Co3O4@Co components contribute significant eddy current loss and polarization effects, while the abundant heterogeneous interfaces between the conductive Fe-THBQ and magnetic Co3O4@Co facilitate multiple scattering, magnetoelectric coupling, and interfacial polarization. Overall, this work provides a novel strategy and solid theoretical foundation for the rational design of high-performance, non-pyrolyzed conductive MOF-based broadband microwave absorbers.
For communication and radar stealth applications, microwave absorbing materials urgently need to achieve efficient attenuation and stable operation within limited thickness. However, while continuous conductive networks or high-load loss phases can enhance attenuation, they are prone to impedance mismatch due to excessively high surface dielectric response; simply using low-polarity polymers for coverage may weaken the internal active interface, making it difficult to coordinate wave entry and energy conversion. To address this, we propose a “fluorocarbon-gating–buried-interface dissipation” strategy to construct polytetrafluoroethylene (PTFE)/poly(vinyl alcohol) (PVA)-based porous composite foams containing short carbon fibers (CFs) and cobalt oxide (CoOx) domains, hereafter denoted PPCFCs. Following the immobilization of Co2+ precursors on acidified short carbon fibers, PTFE/PVA foaming, and N2/air stepwise thermal reconstruction, the resulting composite exhibits an F-rich surface composition and a low-order carbonaceous matrix containing embedded, locally dispersed CoOx/CFs-related nanocrystalline domains. The fluorocarbon surface helps mitigate impedance abrupt changes at the air/material interface and reduces liquid-phase wetting, while the porous framework extends the propagation path. Internally, non-penetrating CFs microcurrent units and CoOx nanodomains synergistically induce confined charge migration, multi-level polarization relaxation, and auxiliary magnetic response. The optimal PPCFC-3 achieves a minimum reflection loss of −52.61 dB at 2.8 mm and effective X-band coverage at 3.4 mm. Simultaneously, this material exhibits high apparent hydrophobicity and effective barrier against corrosive media penetration. This study provides a spatial partitioning design approach for optimizing porous microwave absorbing materials through the synergistic effect of surface impedance tuning and internal interface dissipation.
Developing efficient and robust electrocatalysts is a key challenge for alkaline hydrogen evolution reaction (HER). This work presents Ag-doped Ni4Mo/MoO2 heterostructure toward high-performance alkaline HER. Metallic Ag induces strong electronic modulation, triggering valence electron cloud shift and local electron density redistribution at Ni and Mo sites. Density functional theory (DFT) calculations confirm that Ag incorporation effectively downshifts the d-band center of metallic active sites. The lowered d-band weakens the p–d orbital hybridization between metal sites and interfacial water, thereby increasing the proportion of weakly hydrogen-bond K+ hydrated water (K·H2O). In addition, the tuned electron density of Ni optimizes the adsorption strength of hydrogen intermediates. Accordingly, the Ag-Ni4Mo/MoO2−x delivers superior HER activity, requiring only a 138 mV overpotential to reach a current density of 1 A cm−2 in 1.0 M KOH. We further construct a urea-assisted water electrolysis device with identical Ag-Ni4Mo/MoO2−x electrode for both HER and urea oxidation reaction (UOR) in 1.0 M KOH + 0.33 M urea electrolyte. The integrated electrolyzer achieves 1 A cm−2 at a low cell voltage of 1.62 V. This electronic modulation strategy via metal doping offers a facile route to fabricate bifunctional heterostructure electrocatalysts toward energy-saving hydrogen generation.
Aqueous zinc-ion batteries (AZIBs) are attracting widespread attention due to their high safety and low cost. However, the irreversible phase transformation of the V2O5 cathode into inactive by-products, driven by vanadium dissolution and the accumulation of interfacial OH−, remains a key challenge hindering their practical application. Coupling in situ monitoring with post-mortem analysis, we trace the interfacial chemical processes underlying this failure mechanism. Experimental and theoretical analyses reveal that the accumulation of interfacial OH− leads to a severe local increase in pH, thereby triggering the accelerated precipitation of by-products and the concurrent oxidative dissolution of vanadium. Guided by this mechanistic insight, we introduce sodium gluconate as an electrolyte additive rather than modifying the bulk cathode material. Density functional theory (DFT) calculations confirm that the gluconate anion preferentially adsorbs onto the V2O5 surface, establishing a highly competitive hydrophobic passivation layer. More importantly, this additive forms a dynamic acid-base buffering system at the interface that directly neutralizes locally accumulated OH−, completely suppressing drastic pH fluctuations. By coupling this pH buffering with surface passivation and Zn2+ complexation, the irreversible phase transition of V2O5 is arrested. Consequently, the Zn||V2O5 battery delivers a peak specific capacity of 290 mAh∙g−1 at 0.2 A∙g−1, with 82% capacity retention after 500 cycles, while the preserved V2O5 framework ensures excellent rate performance. Ultimately, isolating this molecular-level dissolution-precipitation trigger establishes a highly general design paradigm—integrating interfacial buffering, multi-site adsorption, and ion complexation—for stabilizing conversion-type cathodes in aqueous batteries.
The development of high-performance electromagnetic wave (EMW) absorbing materials with both strong attenuation capability and favorable biocompatibility is increasingly important for emerging applications in wearable electronics, implantable devices, and portable medical equipment. In this study, we present a class of hollow magnetic carbon nanofibers (Ni/HCNFs) with precisely controlled curvature, fabricated via electrospinning combined with sacrificial template method and subsequent high-temperature carbonization. By tuning the diameter of SiO2 nanospheres, the internal cavity size and geometric curvature of the nanofibers are systematically regulated. The optimized Ni/HCNFs with 300 nm cavities exhibit an outstanding minimum reflection loss of −58.7 dB and an effective absorption bandwidth of 5.28 GHz. The enhanced EMW absorption is attributed to the synergistic effects of impedance matching optimization, multiple reflections within hollow cavities, and intensified interfacial/dipolar polarization losses originating from curvature-induced lattice strain gradients and surface stress fields, as verified by density functional theory calculations and finite element simulations. Furthermore, preliminary biocompatibility assessments indicate that the Ni/HCNFs exhibit low cytotoxicity and good cell viability when co-cultured with fibroblast cells, suggesting their potential as safe and efficient EMW absorbers for future bio-integrated electronic systems. This work not only provides a robust strategy for designing lightweight and high-performance EMW absorbing materials but also opens a new avenue for their application in biocompatible, targeting microwave hyperthermia carrier and environmentally adaptive scenarios.
Developing lightweight electromagnetic wave (EMW) absorbers with excellent high-temperature stability is highly desirable for aerospace and extreme-environment applications. Herein, a SiC@C aerogel (SCA) with a hierarchical porous structure and a nanowire-microfiber multiscale conductive network was fabricated via an in-situ carbothermal reduction strategy. The hierarchical porous architecture promoted EMW multiple scattering, while the interconnected conductive network and abundant SiC@SiO2 heterogeneous interfaces enhanced conduction and polarization losses. The optimized SCA achieved excellent microwave absorption performance, with a minimum reflection loss (RLmin) of −45.9 dB and a maximum effective absorption bandwidth (EABmax) of 3.2 GHz. After oxidation at 800 °C, SCA still exhibited an RLmin of −30.6 dB and an EABmax of 2.72 GHz, which indicates that SCA has strong high-temperature stability in EMW absorption performance. DFT calculations revealed that the formation of a SiC@SiO2 heterointerface promoted interfacial electron transfer and polarization, thereby enhancing dielectric loss. Furthermore, SCA has a density of only0.11 g cm−3, and also exhibits excellent thermal stability and insulation properties. This work provides a novel strategy for designing and developing next-generation multifunctional electromagnetic wave absorbing materials that combine efficient wave absorption with extreme thermal stability.
Tailoring the electronic interaction at the interface between semiconductor catalyst supports and deposited cocatalysts affords a refined strategy to precisely manipulate the electronic states of the active centers residing in the cocatalysts, and concomitantly promote their catalytic efficacy. Herein, we report the fabrication of Pt-CCNS, a model system consisting of Pt nanoparticles supported on cyano-rich crystalline g-C3N4 nanosheet, which manifests highly uniform Pt dispersion and a strengthened interfacial electronic interaction with the underlying g-C3N4. Compared with conventional Pt nanoparticle-modified g-C3N4 (Pt-CN), the introduced cyano groups in Pt-CCNS play a dual role. They not only enable uniform dispersion of Pt cocatalysts on the crystalline g-C3N4 surface, but also effectively promote charge transfer from the g-C3N4 substrate to Pt sites. This enhanced electron flow consequently optimizes the adsorption behavior of hydrogen reaction intermediates on the Pt active centers. Benefiting from the optimized electronic structure and interfacial charge transfer, the optimized Pt-CCNS0.1 photocatalyst delivers a prominent hydrogen-evolution rate of 596.7 μmol h-1, outperforming Pt-CN by a factor of 2.8 and pristine g-C3N4 by a factor of 29.6. This investigation elucidates the intricate interfacial electronic interactions in cocatalyst-modified photocatalytic systems and, more importantly, establishes a robust paradigm for the rational construction of high-efficiency photocatalysts.
Photocatalytic H2O2 synthesis is commonly dominated by the oxygen reduction reaction (ORR), whereas simultaneously enabling water oxidation reaction (WOR) and directional charge separation through band-structure regulation remains challenging. Herein, sulfur doping and pyridine modification were integrated to construct an intramolecular donor-π-acceptor (D-π-A) network within the carbon nitride framework. The resulting electronic polarization promotes directional separation of photogenerated charge carriers and optimizes the band structure to thermodynamically enable both ORR and WOR pathways. Consequently, the as-synthesized SCN-AP photocatalyst achieves an H2O2 yield of 1030 μmol g-1 within 2 h in pure water, 3.73 times that of pristine PCN, and exhibits effective antibacterial activity against clinically relevant pathogens including Acinetobacter beijerinckii and Klebsiella variicola. The in-situ electron paramagnetic resonance (EPR) spectroscopy and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) collectively support the coexistence of ORR and WOR pathways. The ORR serves as the predominant route and involves a ·O2--mediated stepwise reduction pathway together with a 1O2-associated pathway, while WOR provides a complementary hole-driven contribution to H2O2 formation. This work demonstrates a feasible band-engineering strategy for constructing polymeric photocatalysts with directional charge transfer and dual-pathway H2O2 photosynthesis.
Spin polarization control can suppress the recombination of photogenerated carriers at the intrinsic electron spin level, significantly enhancing charge separation efficiency. This study proposes a synergistic strategy combining spin polarization with an S-scheme heterojunction. Specifically, Co doping is introduced into BiOCl nanosheets via a coupled hydrothermal-calcination method to induce spin polarization. Meanwhile, the material is coupled with cubic Co3O4 to construct a 0.5Co-BOC/Co3O4 S-scheme heterojunction. DFT calculations, VSM, and KPFM characterizations collectively confirm that Co doping induces asymmetric occupation of spin-polarized electronic states near the Fermi level of BOC. This narrows the bandgap and promotes charge transfer. The work function difference drives interfacial electrons to transfer directionally from Co3O4 to 0.5Co-BOC, forming a built-in electric field. This built-in electric field drives the spatial directional separation of photogenerated carriers. Meanwhile, spin polarization regulates the spin states of carriers and suppresses spin-matched recombination. Their synergy achieves dual regulation of “spatial separation + spin-forbidden effect”, significantly enhancing carrier separation efficiency and interfacial transport kinetics. Under optimal conditions, the degradation rate of CIP reaches 95.4% within 80 min. This is 1.50 times that of pristine BOC and 4.79 times that of pristine Co3O4. LC-MS and T.E.S.T. assessments indicate that CIP is degraded stepwise via multiple pathways, with significantly reduced toxicity of the intermediate products. This study elucidates the mechanism of synergistic enhancement of carrier separation by spin polarization and the built-in electric field, providing new insights for designing efficient photocatalytic systems.
Covalent organic framework (COF) is a highly promising photocatalyst for hydrogen peroxide (H2O2) photosynthesis, but its photocatalytic performance is limited by slow exciton transfer dynamics and poor reaction selectivity. Herein, we report a p-π conjugation engineering strategy by introducing chlorodiphenylphosphine units into COF framework (CTDDD-P), thereby enabling precise modulation of excited-state electronic structures and the H2O2 photosynthesis pathway. Phosphorus functionalization significantly enhances the photocatalytic H2O2 production performance and reaction stability of COF in air. Theoretical calculations reveal that p-π conjugation induces significant electronic delocalization, strengthens spin-orbit coupling, and reduces the singlet-triplet energy gap, thereby promoting intersystem crossing process. More importantly, femtosecond transient absorption spectroscopy directly resolves the ultrafast processes of exciton evolution and demonstrates the accelerated transition from singlet to triplet excitons and the prolonged triplet lifetime. In situ electron paramagnetic resonance spectroscopy and radical scavenging experiments demonstrate that the H2O2 photosynthesis mechanism is primarily driven by a triplet exciton energy transfer pathway, rather than the traditional oxygen reduction pathway involving superoxide radicals. The triplet exciton can effectively sensitize ground-state triplet oxygen to generate singlet oxygen, thereby increasing the selectivity of H2O2 production. This work has successfully modulated the electronic structure through p-π conjugation and achieved highly efficient triplet exciton generation, providing new insights into the design of high-performance COF-based photocatalysts.
Single-molecule magnets (SMMs) have attracted considerable attention as promising candidates for next-generation spintronic devices. Their magnetic bi-stability, however, is limited by spin-lattice relaxation, a process in which molecular spins dissipate energy to lattice phonons. Since the relaxation dynamics are dictated by the spin’s chemical environment, establishing a direct theoretical connection between molecular structure and relaxation behavior is essential for rational molecular design, despite the inherent complexity of the underlying mechanisms. Here, we explore the mechanism of the Orbach process by reducing the master equation with uniformization method, revealing how the static effective Hamiltonian governs the relaxation energy barrier. To alleviate the heavy cost of calculating thousands of non-equilibrium structures, we propose a new approach that introduces a spin-phonon coupling parameters drawn from a Lorentz distribution. The validity of this simplified protocol is confirmed using seven representative lanthanide SMMs. This work not only deepens the fundamental understanding of Orbach relaxation but also provides an efficient framework for quickly simulating the relaxation behavior of SMMs, thereby facilitating faster targeted molecular design.
