Search Results (5,527)

Biomass-templated spinel ferrite/carbon nanocomposites are promising electrode materials; however, dense carbon shells formed during low-temperature carbonization can block electrolyte access to active sites and impair electrochemical performance. The role of this carbon-shell passivation in biomass-derived ferrite/carbon composites remains largely unexplored. Here, we identify this limitation in a stepwise-synthesized NiFe₂O₄/rGO@C composite (NFC-S, BET surface area = 5.23 m² g⁻¹, ΔEp = 113.3 mV) and resolve it through a rationally designed one-pot optimization strategy in which urea simultaneously serves as a pore-forming agent and nitrogen precursor. The optimized composite (N-NFC-O) achieves a BET surface area of 186.39 m² g⁻¹—a 35.6-fold enhancement—with 70.1% micropore contribution and 3.13 at.% in-situ nitrogen doping. Electrochemically, ΔEp narrows to 72.3 mV and enables efficient NO₂⁻ oxidation with a ~70 mV cathodic shift, whereas NFC-S shows negligible catalytic response under identical conditions. As a proof of concept, differential pulse voltammetry (DPV) yields a nitrite sensitivity of 9.17 µA cm⁻² mM⁻¹ and a detection limit of 92.5 µM. Overall, this work identifies carbon pore accessibility as a key structural descriptor governing electrocatalytic performance in biomass-derived ferrite/carbon composites and provides a general design strategy for developing high-performance biomass-derived carbon/oxide hybrid electrodes. Full article

This work presents an electrochemical, kinetic, and morphological study of iron electrodeposition on a glassy carbon electrode from an ammonium chloride-based electrolyte containing 0.01 M FeCl₂ and 0.1 M NH₄Cl at pH 6.0. Thermodynamic analysis identified [Fe(H₂O)₆]²⁺ as the predominant Fe(II) species under the investigated conditions. Cyclic voltammetry showed a predominantly diffusion-controlled cathodic response at scan rates ≤ 25 mV s⁻¹. At higher scan rates, a marked decrease in cathodic current was observed, which is attributed to the shorter timescale available for Fe nucleation and growth and the reduced contribution of the concurrent hydrogen evolution reaction. Chronoamperometric analysis indicated three-dimensional progressive nucleation and growth under diffusion-controlled conditions. The kinetic parameters revealed a substantial difference between the initial active-site density (N₀) and the nuclear saturation density (Ns), indicating a decrease in the number of sites available for stable nucleus formation as deposition proceeded. SEM characterization showed an increase in particle density and surface coverage with increasing cathodic overpotential, consistent with the potential dependence of the nucleation parameters. Full article

Organic solar cells (OSCs) and perovskite solar cells (PSCs) are emerging photovoltaic technologies owing to their high efficiency, low-cost processing, and diverse applications ranging from utility-scale power generation to small-scale electronics. A key advantage of OSCs and PSCs over traditional silicon-based solar cells is their solution-processability, which enables fabrication via cost-effective scalable printing technologies suitable for commercialization. In addition to organic and perovskite photoactive layers, other functional layers, including interfacial layers and electron and hole transport layers, can also be processed using solution-based printing techniques. However, the conventional architecture of these emerging photovoltaics relies on vacuum-based deposition processes for both oxide-based electrodes (e.g., indium tin oxide and fluorine tin oxide) and metallic top electrodes (e.g., Au, Ag, Cu, and Al), which contrasts with printing-based processing. The implementation of printing technologies for electrode fabrication is necessary to achieve low-cost production and flexible photovoltaic applications. Herein, we review printed electrodes—including metal electrodes, conductive polymers, and carbon-based materials—used to fabricate OSCs and PSCs. Full article

The contribution of the cathode to system-level efficiency in electrochemical oxidation (EO) is rarely isolated from anodic selectivity limitations, even though its influence on cell voltage, hydrogen evolution kinetics, and energy consumption is well recognized. This study presents a multicriteria methodology that deconvolutes cathode performance from these anodic constraints. A stable lead dioxide anode was paired with three cathodes, carbon felt (CF), stainless steel (SS), and titanium dioxide (TiO₂), for Rhodamine B degradation. The methodology combines conventional electrochemical diagnostics, a ten-parameter multicriteria assessment spanning activity, efficiency, and economics, and a sensitivity analysis prioritizing operational metrics. Application revealed that cathode material governs system-level performance through trade-offs between degradation rate and energy consumption: SS minimized cathodic voltage contribution, while CF maximized degradation rate, with sensitivity analysis confirming CF as the optimal practical choice. However, all systems were constrained by a universal limitation: Faradaic efficiencies remained below 0.3% at an applied current of 30 mA, with anode potential well above the oxygen evolution reaction (OER) threshold and more than 99.7% of charge diverted to unwanted water oxidation. Thus, cathode selection modulates cost and yield but cannot resolve the underlying anodic OER limitation. This methodology offers a transferable diagnostic protocol, indicating that future efforts should prioritize integrated system design over single-electrode optimization to overcome EO selectivity limitations. 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

Biowaste-derived porous carbon materials show promise as electrode materials for supercapacitors owing to their low cost, renewable nature, widespread availability, and high specific surface area. Herein, boron and nitrogen co-doped porous carbon was synthesized via a facile one-step activation approach using reed spike as carbon precursor, ammonium borate as both the nitrogen and boron source, and potassium bicarbonate as activator. The prepared PC-700 materials possess large specific surface areas with hierarchical porous architectures and rich N (2.54 at%), O (11.23 at%) and B (2.59 at%) functional groups. As an electrode material, the PC-700 materials show a specific capacitance of 329.6 F g⁻¹ at 0.5 A g⁻¹ and long lifespan. Notably, the assembled PC-700 symmetric super capacitor achieves an energy density of 20.5 Wh kg⁻¹ and excellent electrochemical stabilization (98.60% capacity retention after 10,000 cycles). Full article

Fluorescence-based immunoassays are widely used for sensitive and specific biomarker detection; however, further improvements in sensitivity remain desirable for detecting low-abundance analytes without increasing assay complexity. In this work, we present a proof-of-concept demonstration of guided electrokinetic assembly of functionalized latex beads as a post-assay signal enhancement strategy using alternating-current electro-osmosis (ACEO). Carboxyl-modified 1 μm polystyrene beads conjugated with Alexa Fluor 647-labeled anti-IgG were localized within lithographically defined windows on carbon interdigitated electrode arrays, producing localized fluorescence enhancement through physical bead localization without enzymatic amplification or additional labeling chemistries. Compatibility of the approach with fluorescence-based immunoassays was demonstrated through adaptation of a TNF-α ELISA workflow. Electro-osmotic localization of functionalized bead conjugates was achieved within 120 s, producing an approximately 12-fold increase in corrected total fluorescence relative to the corrected signal of the pre-electro-osmosis condition while demonstrating negligible enrichment of unbound fluorescent protein. Application of the platform to a TNF-α sandwich immunoassay yielded an approximately 5.5-fold enhancement in fluorescence signal, and robust bead localization was maintained across anti-IgG concentrations ranging from 1 to 4 μg/mL. These findings demonstrate that guided electrokinetic bead localization provides an effective signal enhancement strategy for fluorescence-based immunoassays and represents a promising approach for improving the detection of low-abundance analytes. Full article

Integrated electrochemical sensors (IESs) offer rapid and efficient detection of environmental pollutants, but their broader practical implementation requires overcoming common challenges associated with reproducible fabrication and long-term stability. In this work, these challenges were addressed using a thick-film approach to fabricate IESs with graphite-glass, glassy carbon, and carbon black working electrodes (WEs) by screen printing followed by firing at 850 °C. The relationship between the structure of the carbon-based WEs and the electrochemical performance of the IESs was systematically investigated using cyclic voltammetry (CV) in combination with X-ray powder diffraction, transmission electron microscopy (TEM), and scanning TEM. The analyses revealed distinct morphologies and structural ordering of the carbon WEs, which directly affect their electron-transfer kinetics, adsorption behaviour, capacitive response, and electrochemically active surface area. The ordered structure of the graphite-glass WE was associated with lower capacitance and faster electron-transfer kinetics, as determined from the CV response of the IES. In contrast, the disordered structure of the carbon black WE was associated with higher capacitance and slower kinetics of the IES. The glassy carbon-based IES exhibited kinetics similar to those of the carbon black-based IES, but with the lowest capacitance, resulting in the greatest signal definition. Consequently, although all IESs exhibited wide operating potential windows (−1.6 V to +1.0 V vs Ag/AgCl) and fast heterogeneous electron-transfer kinetics towards the [Fe(CN)₆]^3−/4− redox probe (7.6 × 10⁻³–15.5 × 10⁻³ cm s⁻¹), the carbon materials differed in their electrochemical response and signal definition. Importantly, all IESs demonstrated excellent reproducibility (relative standard deviation < 2.4%), operational stability with less than 5% signal loss after 1000 CV cycles, and shelf-life stability exceeding 30 days. These findings demonstrate that tailoring the carbon structure of the screen-printed thick-film WEs enables reproducible fabrication of stable and reliable IESs while providing a versatile strategy for tuning their electrochemical performance towards application-specific requirements. Full article

Molecularly imprinted polymers combined with carbon nanomaterials have proven effective in constructing electrochemical sensors with high selectivity, sensitivity, and robustness. Herein, a polypyrrole-based molecularly imprinted electrochemical sensor was developed on a multi-walled carbon nanotube-modified glassy carbon electrode for homocysteine detection in human serum. The sensor was fabricated via drop-coating of sodium dodecyl sulfate-dispersed multi-walled carbon nanotubes, followed by in situ electropolymerization of pyrrole using homocysteine as the template. The morphology, interfacial properties, and electrochemical behavior of the electrode were systematically characterized by scanning electron microscopy and electrochemical techniques. Under optimized conditions, the sensor showed a linear response to homocysteine in the range of 1.0 × 10⁻¹⁰ mol/L to 1.0 × 10⁻⁵ mol/L, with a detection limit of 7.12 × 10⁻¹¹ mol/L (S/N = 3). The sensor also exhibited good selectivity against common interferents, as well as acceptable reproducibility and stability. Recovery tests in human serum yielded recoveries of 91.00~110.50% (average: 100.73%), demonstrating its potential for practical homocysteine analysis in complex biological matrices. Full article

Additive manufacturing provides a fabrication route for electrode components with controlled macrostructure; however, printable carbon inks that also incorporate oxygen reduction reaction active precursors remain underdeveloped. Here, XC-72 carbon was combined with selected metal precursors to prepare N–C, Fe–N–C, and Pt-containing carbon ink formulations for direct ink writing. The precursor mixtures were incorporated into a polyurethane-based matrix, pyrolyzed at 900 °C, and characterized using X-ray diffraction, oscillatory rheology, rotating ring-disk electrode measurements, Brunauer–Emmett–Teller surface-area analysis, and scanning electron microscopy. XRD confirmed retention of carbon diffraction features and the formation of metal-containing crystalline phases after pyrolysis. Oscillatory rheology showed storage moduli exceeding loss moduli for the tested formulations, indicating elastic-dominant behavior suitable for shape retention during printing. For the PGM-free formulations, incorporation of nitrogen and iron precursors improved ORR onset potential, half-wave potential, limiting current density, and electron-transfer selectivity relative to the carbon control. BET analysis showed a decrease in accessible surface area after precursor incorporation, consistent with partial pore blocking or structural modification during pyrolysis. These results establish a printable formulation platform for ORR-active carbon-based inks, while future work is required to isolate the effects of printed architecture, pore hierarchy, and durability under fuel-cell operating conditions. Full article

Supercapacitors offer high power density, fast charging/discharging capability, and long cycle life, yet their relatively low energy density limits broader deployment in electric vehicles, portable electronics, and grid storage systems. MXenes, a family of two-dimensional transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrode materials due to their high electrical conductivity, tunable surface chemistry, hydrophilicity and intrinsic pseudocapacitive behavior. However, restacking of MXene layers reduces accessible surface area and ion transport efficiency, constraining electrochemical performance. To address this limitation, MXene-based nanocomposites incorporating carbon nanomaterials, conducting polymers, and metal oxides have been extensively developed. This review systematically evaluates recent advances in MXene-based nanocomposites for high-energy-density supercapacitors, highlighting electrochemical performance. A quantitative benchmarking comparison with commonly used electrode materials, including graphene, carbon nanotubes, and activated carbon, is provided. Key challenges in synthesis, performance standardization, and stability are discussed, along with future prospects for developing safer and scalable production methods of MXene-based electrodes. Full article

Monitoring dopamine (DA) in pork can provide useful information for assessing meat freshness and quality deterioration. In this work, an Fe@N-S-O-C nanocomposite was fabricated as an electrode modifier for DA determination. The Fe@N-S-O-C nanocomposite was synthesized via precipitation followed by calcination using melamine and ferrous sulfate as precursors. The crystal structure, surface chemical composition, and morphology were characterized by XRD, XPS, SEM, and TEM. The Fe@N-S-O-C-modified glassy carbon electrode (Fe@N-S-O-C/GCE) was then evaluated for its electrocatalytic performance toward DA. Under the optimized conditions (pH 6.0), the sensor showed linear responses to DA over 1–65 and 65–220 μM. The sensitivities for these two ranges were 4.357 and 1.685 μA μM⁻¹ cm⁻², respectively, with an LOD of 40 nM. In addition, the Fe@N-S-O-C/GCE showed excellent reproducibility, good repeatability, and strong anti-interference capability against common coexisting substances. After 30 days of storage, 82.74% of the initial current response was retained by the same electrode. Practical applicability of the sensor was verified in pork samples, with recoveries of 95.97–106.73%. These results demonstrate that the Fe@N-S-O-C/GCE sensor offers a reliable and effective platform for DA detection in complex food matrices. Full article

Copper and lead contamination in loess areas poses a potential threat to soil environmental quality and sustainable land use, while the low permeability, high clay content, and strong buffering capacity of loess often limit the efficiency of conventional electrokinetic (EK) remediation. This study developed an enhanced EK system integrating novel hydrogel (NH) electrodes, a poly(diallyldimethylammonium chloride)-modified activated carbon/carbon fibre (MAC/CF) permeable reactive barrier (PRB), and a vertical voltage for the remediation of Cu- and Pb-contaminated loess. The effects of vertical voltage (0, 10, 20, 30, and 40 V) on EK behaviour, contaminant migration, and removal performance were investigated. The results showed that the MAC/CF PRB improved electrical stability, enhanced electroosmotic transport, and regulated pH evolution by providing conductive pathways and reactive sites for OH⁻ capture and metal adsorption. Compared with the system without a PRB, the accumulated electroosmotic flow (EOF) increased from approximately 680 to 980 mL. The vertical voltage further promoted Cu²⁺ and Pb²⁺ redistribution into the PRB and enhanced the migration–adsorption coupling process. The optimal voltage of 30 V achieved the best remediation performance, with Cu and Pb removal efficiencies of 69–80% and 32–36%, respectively, within 72 h at initial concentrations of 500 mg kg⁻¹. Mechanistic analysis revealed that the vertical voltage transformed the MAC/CF barrier from a passive adsorption layer into an electrically activated migration–capture interface. The synergistic effects of ion transport regulation, OH⁻ buffering, conductive network construction, and heavy metal adsorption effectively suppressed precipitation-induced focusing and improved remediation efficiency. This study provides a promising strategy for enhancing EK remediation of low-permeability and structurally sensitive soils. Full article

Firefighters are exposed to complex smoke containing volatile, semivolatile, aromatic, and particulate-associated organic contaminants that accumulate on skin, clothing, and protective equipment. Conventional gas sensors monitor only selected airborne species, while passive samplers require laboratory analysis and cannot provide continuous exposure assessment. To address this limitation, we developed a proof-of-concept mass-capacitor that integrates contaminant absorption and electrical sensing within a single polydimethylsiloxane/functionalized carbon nanotube (PDMS/f-CNT) composite coated on interdigitated electrodes (IDEs). Unlike conventional sensors that report the instantaneous concentration of selected compounds, the proposed platform functions as both a sorptive collector and an electrical transducer. It continuously converts contaminant uptake, retention, and release into a time-resolved electrical response. For firefighter applications, this mass-capacitor bridges the gap between passive sorptive samplers and conventional real-time gas sensors. It enables continuous tracking of the cumulative sorbed contamination burden without requiring offline laboratory analysis or restricting the measurement to selected airborne species. A custom potentiostat applied staircase cyclic excitation, while Fast Fourier Transform (FFT)-assisted processing enabled extraction of the differential charge, $\mathsf{\Delta }Q$ as an indicator of contaminant loading. The sensor was evaluated using smoke generated from cotton, paper, wood, and synthetic fibers. Compared with PDMS alone, the PDMS/f-CNT composite produced an approximately 24-fold higher response with minimal humidity interference (≈80% RH). Limits of detection ranged from 0.08 to 0.26 ppm, while repeated smoke exposures produced stepwise increases in ΔQ, demonstrating continuous tracking of cumulative contaminant loading. These results establish the feasibility of the mass-capacitor concept and introduce a new approach for real-time monitoring of the accumulated organic contamination burden rather than the instantaneous concentration of individual airborne compounds. Full article

Lithium–sulfur batteries have become one of the research focuses of scientists over the past decade due to their high theoretical specific capacity (approximately 1670 mAh/g), low cost, and environmental friendliness, and the abundant reserves of their raw materials. Nevertheless, they still suffer from inherent drawbacks including poor electrical conductivity of elemental sulfur, electrode volume expansion during charge–discharge cycles, the shuttle effect and lithium dendrite growth, which severely restrict their practical application and industrialization. To address the above issues, extensive research has been carried out to optimize cathode materials, separators and electrolytes. In particular, the shuttle effect occurring during cycling can be effectively mitigated via separator modification. This paper briefly introduces the design strategies for separators for lithium–sulfur batteries, and mainly summarizes separator-modification methods using carbon materials, graphene, carbon nanotubes, heteroatoms, polymers, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). Finally, the future development trends of lithium–sulfur batteries are prospected. Full article