Search Results (464)

Commercial carbon-based electrodes such as graphite felt and carbon felt in all-vanadium redox flow batteries suffer from inherent drawbacks, including slow vanadium ion redox kinetics, insufficient intrinsic catalytic activity, fiber corrosion, and functional group loss under strong acidic oxidative conditions, significantly limiting battery energy efficiency and long-term operational reliability. Rare-earth elements, with their unique 4f electron shell structure, tunable electronic levels, abundant surface oxygen vacancy defects, and strong coordination ability, offer a dual pathway—electronic and microstructural modulation—to optimize the interfacial electrocatalytic behavior of carbon electrodes, providing a novel materials system to overcome electrode performance bottlenecks in vanadium batteries. This review systematically summarizes recent advances in rare-earth-functionalized carbon electrodes and electrocatalysts for vanadium redox flow batteries, elaborating on core modification strategies, performance enhancement trends, and synergistic catalytic mechanisms. It also presents quantitative experimental results from the literature to clearly demonstrate the benefits: CeO₂-modified graphite felt at 0.2 wt% shows a 10.8% increase in energy efficiency compared to pristine graphite felt at a current density of 200 mA·cm⁻², while multi-rare-earth co-doped carbon electrodes achieve a 65% reduction in charge transfer resistance relative to unmodified electrodes. The review systematically categorizes two dominant modification routes—surface nano-decoration with rare-earth oxides and lattice bulk doping with rare-earth elements—and summarizes design principles and enhancement mechanisms of diverse composite catalytic systems, including rare-earth–carbon nanocomposites, rare-earth-based heterojunctions, and porous rare-earth catalysts. It further analyzes critical challenges in current research, such as unclear long-term stability mechanisms, high costs of high-purity rare-earth raw materials, immature large-scale fabrication processes, and limited in situ dynamic characterization techniques. Compared with existing reviews, this work clearly distinguishes between surface loading and lattice doping as two distinct rare-earth modification approaches, clarifying their differences in active site formation, electronic regulation logic, and cycling stability. It establishes a comprehensive theoretical framework for the coupled electronic–geometric effects in rare-earth-modified carbon electrodes, linking the intrinsic physicochemical properties of rare earths, material microstructure design, and battery electrochemical performance. Moreover, it innovatively proposes a pathway toward full-lifecycle recycling and reuse of rare-earth-based catalytic electrodes for industrial implementation. This review provides a complete theoretical foundation for developing high-performance, long-cycle, low-cost vanadium redox flow battery electrode materials and supports their engineering scale-up, contributing to the development of large-scale, long-duration energy storage technologies. Full article

The electrocatalytic nitrogen reduction reaction (NRR) is a key approach for synthesizing green ammonia under mild conditions. However, the high bond energy of the N≡N triple bond makes N₂ difficult to activate, limiting the Faradaic efficiency. MoS₂ offers advantages such as low cost and abundant reserves as a non-precious-metal NRR electrocatalyst. Nevertheless, pure MoS₂ suffers from insufficient conductivity and a limited number of active sites, resulting in suboptimal catalytic performance. Herein, we develop a solvent-regulated one-step hydrothermal strategy using ethylene glycol as the sole reaction medium to fabricate an oxygen-substituted amorphous MoS₂ (O-MoS₂) electrocatalyst. XRD, SEM, and HRTEM characterization revealed that, as the ethylene glycol ratio increased, the product gradually transformed from a layered crystalline structure to a completely amorphous structure. XPS confirmed that oxygen atoms were uniformly incorporated into the MoS₂ lattice via substitution doping. Electrochemical testing showed that O-MoS₂ achieved an ammonia yield of 97.16 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 46.44% in a 0.1 M Na₂SO₄ electrolyte at −0.70 V vs. RHE, significantly outperforming undoped MoS₂ and semi-doped S-MoS₂. DFT calculations indicate that O doping reduces the N₂ adsorption energy, thereby synergistically promoting N₂ adsorption and activation. This dual-modification strategy provides a facile and universal guidance for electronic structure regulation of MoS₂-based catalysts and sheds new light on the design of high-efficiency ambient nitrogen fixation electrocatalysts toward practical green ammonia synthesis. Full article

Biomass-derived nanoengineered carbon materials have emerged as key platforms in environmental technologies due to their high surface area, electrical conductivity, chemical stability, and sustainable synthetic route starting from renewable feedstock. This broad family comprises dimensionally nanoscale materials, such as carbon dots, carbon nanofibers, and graphene-based structures, as well as biochars, hydrochars, activated carbons, and related porous carbonaceous materials whose pore architecture, surface chemistry, or defects are deliberately engineered at the nanometer scale. Beyond their traditional role as passive supports, these materials can actively regulate adsorption phenomena, charge transport, and catalytic microenvironments through precise control of heteroatom doping, graphitic domains, and hierarchical porosity. Among current environmental priorities, carbon dioxide (CO₂) management represents one of the most pressing challenges. Biomass-derived nanocarbons offer tunable adsorption sites for selective CO₂ capture while simultaneously serving as active matrices for catalytic conversion. Tailored doped-carbon frameworks can stabilize key reaction intermediates, suppress competing pathways such as hydrogen evolution, and promote selective transformation into fuels and high-value chemicals. In addition, these materials are excellent hosts for atomically dispersed metals, dual-site catalysts, and semiconductor hybrids used in electrochemical and photocatalytic CO₂ reduction. By combining renewable sourcing with nanoscale control of reactivity, carbon materials create a bridge between environmental remediation and carbon valorization. This review critically examines recent progress in biomass-derived nanoengineered carbon materials for integrated CO₂ capture and conversion, with emphasis on structure-property-performance relationships, mechanistic roles, scalability, and sustainability. Particular attention is also devoted to catalytic conversion and electrochemical CO₂ sensing, where carbon-based and hybrid interfaces enable the transduction of CO₂ recognition into measurable electrical responses. These materials represent a promising yet underexplored pathway toward circular carbon management and the development of next-generation low-carbon chemical technologies. Full article

Phenolic resin pyrolytic carbon is a key matrix phase in carbon-based refractories and carbon/carbon composites; however, its defect-rich glassy carbon structure exhibits poor oxidation resistance at elevated temperatures. In this work, we report a facile one-step thermal-treatment strategy using melamine as a nitrogen source to prepare nitrogen-modified phenolic resin pyrolytic carbon (NC). The structural evolution and oxidation behavior of samples carbonized at 500–800 °C were systematically investigated by XRD, SEM, TEM, FT-IR, Raman, XPS, BET, and TG-DSC. The results reveal that melamine-derived nitrogen exists in two distinct forms: at 500–700 °C, a carbon nitride-rich phase consistent with graphitic carbon nitride (g-C₃N₄) forms sheet- and belt-like structures on the carbon surface and partially fills the internal pores; at 800 °C, its long-range crystalline signature disappears, while pyridinic, pyrrolic, and graphitic nitrogen remain in the carbon framework. From 500 to 800 °C, the relative N 1s fraction of pyridinic N decreases from 72.33% to 44.38%, whereas graphitic N increases from 0.47% to 24.09%. Meanwhile, the pore structure evolves from a mesopore-dominated architecture with a limited accessible surface area at 500–600 °C to a micropore-rich structure at 700–800 °C. Relative to unmodified PR-800, NC-800 exhibits an approximately 30 °C higher onset oxidation temperature and an approximately 40 °C higher complete oxidation temperature, together with a lower maximum mass-loss rate and a delayed, broadened exothermic response. These results show that melamine-derived pore regulation and skeletal nitrogen doping jointly retard oxygen transport and suppress oxidation-active defect sites, providing a simple and potentially scalable route for improving the high-temperature oxidation resistance of phenolic resin pyrolytic carbon. Full article

Electrocatalytic glycerol oxidation to formic acid (FA) offers a sustainable route for biomass valorization, yet non-noble metal catalysts generally suffer from sluggish C-C bond cleavage and poor product selectivity. Here we report an amorphous nickel–cobalt oxyhydroxide bearing both metal and oxygen vacancies (D-NiCoO_xH_y-V_Cr,O), grown on nickel foam via one-step electrodeposition followed by electrochemical activation with Cr doping. The coexistence of the dual vacancies is experimentally confirmed by X-ray photoelectron spectroscopy (XPS), which reveals elevated Ni³⁺/Co³⁺ ratios and reduced lattice oxygen, and by electron paramagnetic resonance (EPR), which shows a markedly enhanced signal at g = 2.003. Building on prior Cr-leaching approaches in single-metal nickel oxides, this work extends dual-vacancy engineering to an amorphous bimetallic NiCo oxyhydroxide and correlates the defect structure with glycerol-induced interfacial responses, charge-transfer behavior, and product selectivity. The catalyst delivers 200 mA cm⁻² at 1.31 V vs. RHE and achieves 100% Faradaic efficiency for formate at 1.32 V vs. RHE. In situ electrochemical impedance spectroscopy further reveals a significantly reduced charge-transfer resistance. These results establish Cr-assisted dual-vacancy engineering in amorphous bimetallic oxyhydroxides as a promising strategy for selective biomass electrooxidation. Full article

Traditional petroleum coke-based porous carbons suffer from low specific surface area, insufficient surface active sites, and inferior rate and cycling performance. Herein, a series of sulfur/fluorine-co-doped hierarchical porous carbon (S+F-PC) cathode materials were synthesized controllably from industrial solid-waste petroleum coke via KOH high-temperature activation and heteroatom doping strategies. Polyaniline/carbon nanotube (PANI/CNTs) core–shell composites were fabricated as anodes through in situ oxidative polymerization, and S+F-PC//PANI/CNT asymmetric aqueous supercapacitors were assembled. The structural and chemical modulation mechanisms of dual heteroatom doping, as well as the electrochemical energy storage kinetics of electrodes and devices, were systematically investigated using SEM, TEM, XRD, XPS, BET, CV, GCD, EIS, and long-cycle tests. The results verify the synergistic modification effect of sulfur and fluorine co-doping. S-induced lattice distortion creates abundant mesopores and pseudocapacitive active sites, while F atoms stabilize the carbon skeleton to avoid high-temperature structural collapse and enhance the graphitization degree. The optimized S+F-PC exhibits an interconnected micropore–mesopore–macropore hierarchical network and a specific surface area of 172.2 m²/g, delivering a high specific capacitance of 477 F/g at 1 A/g, outperforming pure PC, and single-S-doped and -F-doped counterparts. The PANI/CNTs core–shell structure effectively alleviates the volume expansion of PANI during cycling, and the one-dimensional CNTs form a continuous conductive network. The PANI/CNT anode achieves a specific capacitance of 417 F/g, with a capacity retention of 91.4%, after 10,000 cycles. The assembled asymmetric supercapacitor realizes a stable voltage window of 1.6 V. It presents a specific capacitance of 117 F/g at 1 A/g, a maximum energy density of 41 Wh/kg at a power density of 2000 W/kg, and 87.2% capacity retention after 10,000 cycles. This work provides a feasible strategy for the high-value recycling of industrial-waste petroleum coke and the design of high-performance heteroatom-doped carbon electrodes and matched asymmetric aqueous supercapacitors. Full article

Garnet-structured compounds have long been recognized as versatile host platforms for luminescent phosphors, owing to their robust chemical stability and highly tunable cationic sublattices. Conventional aluminate and gallate garnets, however, generally face intrinsic limitations, including severe concentration quenching at high dopant levels, relatively high phonon energy, and unsatisfactory efficiency for long-wavelength near-infrared (NIR) emission. In recent years, sodium-based germanate garnets, constructed by introducing aliovalent Na⁺ into dodecahedral sites combined with Ge⁴⁺ substitution in tetrahedral frameworks, have emerged as a promising branch of garnet phosphors. The aliovalent Na+ incorporation brings unique structural effects, including energy migration blocking, coordination environment distortion, and defect level modulation, which endow the materials with advantages in mitigating concentration quenching, boosting energy transfer efficiency, and enhancing thermal stability. This review systematically summarizes the crystal structure classification and luminescence fundamentals of sodium-based germanate garnet systems, and introduces mainstream synthesis techniques represented by the high-temperature solid-state method. Focusing on representative host systems, the luminescence characteristics and energy transfer mechanisms of both rare earth- and transition metal-doped systems are elaborated in detail, followed by a summary of four representative performance regulation strategies: cationic disorder engineering, crystal field engineering, defect engineering and dual-site cooperative regulation. The multifunctional applications of these materials in white light-emitting diodes, plant growth lighting, fluorescence temperature sensing, NIR imaging, and information encryption are also presented. Finally, existing challenges and future research perspectives are proposed to provide guidance for the development of high-performance garnet phosphors. Full article

The development of sustainable, smart food packaging materials that simultaneously provide antimicrobial protection and real-time monitoring of food quality is a critical frontier in food safety. This study reports the fabrication of a multifunctional amphiphilic emulgel designed for the detection of pathogen-induced metabolic pH changes in food systems. The system utilizes Pomegranate-derived nitrogen-doped quasi-spherical carbon dots (QS-CDs) as fluorescent nanoprobes and Rosemary Essential Oil (REO) as a natural antimicrobial agent, both encapsulated within a polyelectrolyte complex of chitosan and sugarcane bagasse-derived carboxymethyl cellulose (CMC). A low degree of substitution (DS = 0.4) was specifically engineered for the CMC to ensure an amphiphilic character, enabling nanocomposite complex stabilization of the REO droplets without synthetic surfactants. Structural characterization via Transmission Electron Microscopy (TEM) revealed well-dispersed QS-CDs (4.71–6.62 nm) and stable oil droplets (~605.49 nm) anchored within a zipped polymer network. Thermal analysis (TGA/DSC) using the Coats–Redfern model revealed a significant synergistic effect: the smart-emulgel exhibits a distinct two-stage degradation profile, with the high-temperature stage requiring an activation energy (E_a) of 95.19 kJ/mol, a substantial increase over the corresponding stage in the CD-emulgel baseline (18.69 kJ/mol). This enhanced stability is complemented by a slight increase in crystallinity (X_c from 0.11 to 0.14). While the smart-emulgel remains predominantly amorphous, this shift suggests that the integration of REO and QS-CDs into the polymer network promotes the formation of localized, more ordered domains, contributing to a more robust and structurally integrated matrix. The emulgel demonstrated a dual-mode optical response (colorimetric and fluorometric) sensitive to the metabolic byproducts (e.g., organic acids, amines, other alkaline compounds) produced by Escherichia coli and Staphylococcus aureus. These findings were corroborated by Density Functional Theory (DFT) calculations, which confirmed the thermodynamic stability and optimized electronic energy gaps for pH-responsive sensing. This research provides a green, high-performance platform for the real-time monitoring of food freshness and the prevention of foodborne illnesses. Full article

Developing high-performance n-type polymer semiconductors is hindered by the scarcity of strong electron-deficient building blocks. Herein, we report a dual-functionalization strategy that integrates both quinoid and cyano groups into polythiophene backbones to construct n-type polymers. Two new polymers, PQTTCN and PQTVTCN, were synthesized via the Stille copolymerization of a thienoquinoid-based dibrominated monomer (TTD2T-Br) with cyano-functionalized bithiophene and thienylene-vinylene-thienylene distannyl monomers, respectively. Electrochemical and computational analyses confirm that both polymers exhibit low-lying LUMO levels of −4.07 eV and highly planar backbones. In organic field-effect transistors, PQTTCN and PQTVTCN show unipolar n-type charge transport, with electron mobilities of 0.036 and 0.002 cm² V⁻¹ s⁻¹, respectively, which are attributed to their deep frontier molecular orbitals and planar conformations. Upon doping, both polymers exhibit n-type thermoelectric performance, achieving an electrical conductivity and power factor values of 0.16 S cm⁻¹ and 0.75 μW m⁻¹ K⁻² for PQTTCN and 0.043 S cm⁻¹ and 0.17 μW m⁻¹ K⁻² for PQTVTCN, respectively. AFM and GIWAXS results demonstrate that PQTTCN has better dopant compatibility and higher crystallinity than PQTVTCN. This work highlights that the combination of quinoid and cyano units offers a promising strategy for developing high-performance n-type polymer semiconductors for organic electronics. Full article

Efficient removal of tetracycline (TC) from antibiotic-contaminated wastewater remains a significant challenge. In this study, a nitrogen-doped carbon modified cobalt ferrite (C@CoFe₂O₄, CF) composite was synthesized via a one-step hydrothermal method, and its adsorption–catalysis dual-function performance was systematically evaluated. Structural characterization revealed that CoFe₂O₄ nanoparticles were locally encapsulated by an N-doped carbonaceous layer, providing a high specific surface area and abundant nitrogen-containing active sites. Under optimized conditions, the CF-3/PMS system achieved 93.44% TC removal within 45 min, while CF-3 exhibited a maximum adsorption capacity of 486.5 mg·g⁻¹. Radical quenching experiments suggested that singlet oxygen (¹O₂) and superoxide radicals (O₂•⁻) played major roles in TC oxidation, while sulfate radicals (SO₄•⁻) and hydroxyl radicals (HO•) also contributed, indicating the coexistence of radical and non-radical oxidation pathways. TC adsorption was driven by surface complexation, π–π electron donor–acceptor interactions, and hydrogen bonding. The enhanced TC removal performance may arise from the cooperative contributions of N-containing carbon sites, accessible Co/Fe-containing regions, and interfacial electronic interactions, which promote TC enrichment and PMS-mediated oxidation. This work provides a promising strategy for designing bifunctional materials for antibiotic wastewater treatment. Full article

Silicon carbide (SiC) in its various structural modifications is widely used in power semiconductor electronics, operating under extreme conditions of high temperature, high voltage, and intense radiation. The discovery of spin defects (S > 0) with unique optical and coherent properties has further positioned SiC as a promising platform for quantum technologies. Here, we investigate a 6H-SiC single crystal co-doped with nitrogen and beryllium at concentrations of 10¹⁸ cm⁻³, using continuous-wave and pulsed electron paramagnetic resonance (EPR) and electron–nuclear double resonance (ENDOR). To enhance spectral resolution, experiments were conducted in the W-band (94 GHz; B = 3.4 T). Pulsed EPR identified nitrogen donors and beryllium acceptors in various lattice positions, allowing for the determination of their phase coherence and spin–lattice relaxation times. ENDOR measurements elucidated the electron–nuclear interactions with the local silicon and carbon environment, including distant coordination spheres. The observed hyperfine structures indicated highly delocalized spin density within the supercell. The TRIPLE resonance spectra verify coupled nuclear spin subspaces from different coordination spheres due to defect spin density. These results demonstrate the feasibility of incorporating dual impurities with distinct functional roles while preserving the crystal lattice’s structural features. Full article

White LEDs are widely used in fields such as lighting and display. However, existing white light devices suffer from excessively broad emission spectra full width at half maximum (FWHM) and severe leakage of pump blue light. Hence, this study proposes a theoretical design for an ultra-narrow-band white LEDs based on an asymmetric Fabry-Pérot (F-P) microcavity. The microcavity employs a dual-DBR configuration with asymmetric optical responses: the bottom DBRs utilize a ZnS/MgF₂ ($d_L$/2-$d_H$-$d_L$/2)⁵ stack, providing a low reflectance of ~20% at 457 nm for efficient blue light transmission and quantum dot excitation; conversely, the final device incorporating top DBRs with a TiO₂/MgF₂ ($d_H$/2-$d_L$-$d_H$/2)⁴-stacked structure achieved a high reflectivity of approximately 89% at 457 nm, effectively decreasing the excessive blue light in the output spectrum. The intermediate emissive layer uses polymethyl methacrylate (PMMA) as the quantum dot host. By precisely tuning the cavity thickness, the resonant modes of the F-P microcavity—specifically the fourth-order (626 nm) and fifth-order (534 nm)—are aligned with the emission peaks of the red and green quantum dots, respectively. Simulation results demonstrate that the structure leverages the cavity filtering effect to compress the FWHM of the red and green emissions from initial values of 36.5 nm and 29.8 nm down to 2.2 nm and 1.9 nm, respectively, representing an order-of-magnitude improvement in color purity. Through the co-optimization of the top-DBR’s central wavelength, cavity optical thickness, and the doping ratio of red/green quantum dots, standard white light emission with CIE coordinates of (0.32, 0.33) was achieved, accompanied by emission efficiencies of 6.3% (green) and 22.3% (red) for the QDs. However, strict manufacturing tolerances and narrow observation angles limit the applicability of the device. This work provides theoretical research for developing white light sources. Full article

Rapid and matrix–aware evaluation of antioxidant responses in dairy–containing tea beverages remains challenging because milk components may interfere with the detectable activity of tea polyphenols. In this study, a photoactivated Mn–doped carbon nanosheet (Mn–CNS)–based dual–mode nanozyme assay was developed for the rapid evaluation of antioxidant responses in tea beverages and dairy tea matrices. The Mn–CNSs exhibited light–triggered oxidase–like activity toward 3,3′,5,5′–tetramethylbenzidine, enabling synchronized colorimetric and fluorescence readouts within 1 min. Using epigallocatechin gallate as a model antioxidant, the assay showed limits of detection of 0.22 and 0.29 μg/mL in the colorimetric and fluorescence modes, respectively, together with good selectivity and applicability to tea infusions. When applied to milk tea systems, the measurable antioxidant response decreased to 56.9–72.2% of that in corresponding tea infusions, indicating a pronounced matrix–dependent attenuation. Matrix–matched calibration and dual–indicator recovery analysis further distinguished tea infusion recovery from antioxidant response recovery, while molecular docking suggested that β–lactoglobulin–EGCG interactions contributed to the reduced detectable response. These results demonstrate that the proposed dual–mode assay is a rapid tool for antioxidant–response evaluation and highlight the importance of matrix–aware interpretation in complex dairy tea beverages. Full article

Electrocatalytic nitric oxide reduction reaction (NORR) for ammonia synthesis has emerged as a research focus in artificial nitrogen fixation. Unlike previous reviews that primarily focus on experimental catalyst development, this work offers a comprehensive and systematic summary of recent theoretical progress in NORR, with special emphasis on low-dimensional materials. We connect four important areas: atomic-level design principles for active sites, emerging mechanistic ideas that go beyond conventional scaling relations, realistic simulations of the electrochemical microenvironment, and data-driven machine learning approaches for catalyst discovery. We begin by discussing the reaction mechanism, analyzing the orbital interactions that control NO activation and the thermodynamic and kinetic features of different reaction pathways. For active-site construction, we examine electronic synergy in single-atom and dual-atom catalysts, coordination microenvironment tuning, electronic structure modulation through doping and strain, and heterojunction interfaces that allow multi-degree-of-freedom regulation. To explore new mechanistic concepts, we introduce p-block element synergy, reverse activation, magnetic and spin control, and surface electronic singularities as strategies to overcome traditional scaling relations. Regarding the reaction microenvironment, we analyze how coverage, solvation, local pH, and applied potential jointly affect selectivity and activity. Finally, we summarize the role of machine learning in building descriptors and accelerating catalyst screening. This review aims to provide theoretical guidance for the rational design of efficient NORR electrocatalysts with high activity, selectivity, and long-term stability. Full article

Industrial automation and the Internet of Things (IoT) are driving demand for optical access networks capable of supporting massive connectivity with deterministic low latency. Conventional passive optical networks (PONs) face scalability and cost limitations in ultra-dense deployment scenarios. Here we propose and experimentally demonstrate a polarization-carrier dual-reuse coherent orthogonal frequency division multiplexing PON (CO-OFDM-PON) architecture enabled by optical frequency comb (OFC) sources. The design maps data and carrier signals onto orthogonal polarization states. This enables carrier reuse for both downstream coherent detection and upstream transmission through injection-locked laser (ILL)-based carrier regeneration at the optical network unit (ONU). We comprehensively characterize the key subsystems. These include the OFC, ILL, and erbium-doped fiber amplifier (EDFA). This ensures stable multi-wavelength generation, carrier regeneration, and enhanced receiver sensitivity under high split ratios. Through simulation and experimental analysis of fiber nonlinearities in industrial PON scenarios, we identify an optimal per-channel launch power of 4 dBm. This power balances sensitivity and link budget requirements. Scalability analysis for standard PON reach is also provided. The system demonstrates 16-channel 100 Gb/s per wavelength downstream 16-QAM OFDM transmission. The link budget exceeds 34 dB with bit error rates (BERs) below the forward error correction (FEC) threshold of 1 × 10⁻². While the coherent ONU architecture offers superior spectral efficiency, it entails higher component costs than direct-detection alternatives due to the required coherent receiver and polarization management components. Full article