Graphite Sheets Research Articles

Iron-Based Layered Perovskite Oxyfluoride Electrocatalyst for Oxygen Evolution: Insights from Crystal Facets with Heteroanionic Coordination.

Mixed-anion compounds have recently attracted attention as solid-state materials that exhibit properties unattainable with those of their single-anion counterparts. However, the use of mixed-anion compounds to control the morphology and engineer the crystal facets of electrocatalysts has been limited because their synthesis method is still immature. This study explored the electrocatalytic properties of a Pb-Fe oxyfluoride, Pb3Fe2O5F2, with a layered perovskite structure for oxygen evolution reaction (OER) and compared its properties in detail with those of a bulk-type cubic three-dimensional (3D) perovskite, PbFeO2F. A Pb3Fe2O5F2 electrode prepared with carbon nanotubes and a graphite sheet as a conductive support and a substrate, respectively, demonstrated better OER performance than a PbFeO2F electrode. The role of specific crystal facets of Pb3Fe2O5F2 in enhancing the OER activity was elucidated through electrochemical analysis. Density functional theory calculations indicated that the Pb3Fe2O5F2 (060) facet with Fe sites exhibited a lower theoretical overpotential for the OER, which was attributed to a moderately strong interaction between the active sites and the reaction intermediates; this interaction was reinforced by the strong electron-withdrawing behavior of fluoride ions. This finding offers new insights for developing efficient electrocatalysts based on oxyfluorides, leveraging the high electronegativity of fluorine to optimize the electronic states at active sites for the OER, without relying on precious metals.

The Peculiarities of Acoustic Normal Waves Propagation in Thin Porous Sheets of Thermally Expanded Graphite

Thermally expanded graphite belongs to a new class of graphite materials with unique physical, chemical and mechanical properties. Acoustic wave velocity is one of the most important characteristics for study of porous materials including thin porous sheets of thermally expanded graphite. In this paper peculiarities of symmetric mode S0 Lamb wave propagation and SH-wave with horizontal polarization in sheets of thermally expanded graphite are experimentally investigated. To determine their velocities a differential measurement scheme on the base of a low-frequency acoustic flaw detector DIO1000 LF and specialized piezoelectric transducers with dry point contact was used. Additionally the longitudinal wave velocity in direction of sheet thickness was determined using piezoelectric transducers based on polyvinylidene fluoride. Indicatrices of normal wave velocities in the rolling plane were plotted and it was shown that the maximum acoustic anisotropy is characteristic for the S0-mode. The velocity minimum corresponds to the longitudinal direction of the rolling plane in which the maximum elongation of gas pores was observed. Influence of thickness and density of thermally expanded graphite sheets on the velocities of normal waves was investigated and presence of the thickness range where the minimum velocity values were observed due to the maximum inhomogeneity of layers formed in the rolling process. Method for determination of dynamic elastic moduli of porous thermally expanded graphite sheets using experimentally measured velocities of normal waves was proposed. It was shown that in the longitudinal direction of the rolling plane the Poisson's ratio took negative values which allow to attribute the specified material to auxetics ones.

Hierarchical Intercalation of Solvated Tetrafluoroborate Anions into Graphite Electrodes: The Case Studies of Methyl Acetate and γ-Butyrolactone Solutions.

Intercalation of anions unlocks graphite as a positive material in energy storage devices, and the performance could be affected by solvents in solutions. In this context, it is vital to investigate the role of solvents in anion intercalation. Herein, a hierarchical intercalation phenomenon, in which different graphite intercalation compounds are generated in the same solution, is studied in lithium tetrafluoroborate (LiBF4) solutions of carboxylate ester solvents γ-butyrolactone (GBL) and methyl acetate (MA). The evolution modes of the graphite cathode structure during electrochemical intercalation and deintercalation are discussed via in situ X-ray diffraction (XRD) measurements. Based on this, the relationship between GICs and potentials, together with concentrations, is compared in detail. Furthermore, various graphite materials with different surface properties are applied to adjust the anions' solvation status inside graphite sheets.

A robust floating oxygen-doped graphitic carbon nitride sheet for efficient photocatalytic CO2 conversion

Photocatalytic CO2 reduction offers a promising approach for converting CO2 into valuable chemicals. However, typical conversion systems suffer from inefficient CO2 mass transfer and complex recycling processes. In this study, we developed a floating sheet as a robust photocatalytic CO2 conversion system by integrating graphitic carbon nitride (CN) nanosheets onto polytetrafluoroethylene (PTFE) fiber membrane, followed by oxygen (O) doping into the CN (CN-O) via oxygen-plasma treatment. The floatable CN-O/PTFE sheet exhibits slight wettability in water under 0.25 MPa of CO2 pressure in our reactor system, facilitating the delivery of dissolved CO2 to the CN-O photocatalyst surface. O-doping enhances the visible light absorption and improves the separation and transport efficiency of photogenerated electrons and holes due to O-doping-induced states in CN. Consequently, the floating CN-O/PTFE system achieves an exceptional photocatalytic CO2 conversion rate of 102.3 μmol g-1h−1, approximately 4.8 times higher than a conventional CN-powder dispersion system in water. Moreover, the sheet demonstrates excellent cycling durability, with no significant exfoliation of the catalytic layer or reduction in CO2 photoreduction activity after 20 consecutive cycles. This study presents a novel approach to designing photocatalytic systems for efficient CO2 conversion.

Experimental study of photovoltaic-thermoelectric systems using thermal interface materials and natural cooling

This study investigates a novel approach to enhancing photovoltaic-thermoelectric generator systems by utilizing advanced thermal interface materials in real-world conditions. The research compares two experimental systems under natural air cooling employing different thermal interface materials: one features a pyrolytic graphite sheet, while the other uses conventional thermal grease, alongside a photovoltaic-only system for reference. An Arduino-based data logger accurately monitored key environmental and operational parameters. At peak solar irradiation, the system with the pyrolytic graphite sheet achieved a surface photovoltaic temperature of 39.01 °C, generating 4.90 W and an overall efficiency of 17.95 %. In comparison, the system with thermal grease had a surface photovoltaic temperature of 48.88 °C, generating 4.67 W with an efficiency of 16.87 %, while the photovoltaic-only system reached a surface photovoltaic temperature of 55.37 °C, producing 4.54 W and an efficiency of 16.42 %. The experimental data’s accuracy and reliability were validated against simulations from previous work, revealing error margins between 1.20 % and 3.03 %. These findings underscore the potential of pyrolytic graphite sheets as effective thermal interface materials to significantly enhance the efficiency and power output of photovoltaic-thermoelectric generator systems, offering valuable insights for optimizing renewable energy technologies.

Outstanding Activity and Durability of Supported NiCo2O4 Nanoparticles for Direct Ethanol Fuel Cells

ABSTRACTThe rational design of noble metal‐free electrocatalysts represents one of the basic stones for fuel cell development. With the exploration of eco‐friendly nanomaterials for the investigated alcohol oxidation process, nickel‐based electrodes have been recognized as the most auspicious anodes with promoted activity and stability. In this work, a series of NiCo2O4 nanoparticles were deposited onto graphite sheets (NiCo2O4/T) introducing varied proportions of cobalt oxide species. Co‐precipitation protocol of the respective metallic hydroxides onto the carbonaceous support was followed with consecutive annealing in an air atmosphere at 400°C. The fabricated mixed metallic oxide nanopowder was physically studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X‐ray analysis (EDX), X‐ray photoelectron spectroscopy (XPS), and selected area electron diffraction (SAED). Uniformly arranged nanoparticles were observed on graphite surface as evidenced by SEM and TEM. The cubic lattice structure of formed NiCo2O4 crystals was also confirmed by XRD through the defined peaks of binary metallic oxides clarifying their successful preparation scheme. The electrocatalytic properties of these NiCo2O4/T nanocatalysts were evaluated for oxidizing ethanol molecules in basic solution. Pronounced oxidation current densities were remarkably measured at NiCo2O4/T electrodes in relation to that at NiO/T. Differing the introduced cobalt oxide content into the synthesized nanocatalyst significantly controlled its catalytic performance. NiCo2O4/T‐20 exhibited the highest activity and stability among the prepared nanomaterials. Much decreased charge transfer resistances were also recorded at this electrode demonstrating its promoted electron transfer characteristics. This work could provide a reasonable route for the simple synthesis of comparable transition metallic oxides with promising attitudes for energy generation purposes.

Impact of ultrasonic probe type, frequency, and static pressure on large-scale graphene exfoliation

The ultrasonic liquid phase exfoliation method has emerged as an essential research direction for graphene preparation due to its cost-effectiveness and ability to minimize defects. However, this method faces challenges related to processing throughput when scaled up for industrial production. In this study, industrial grade ultrasonic homogenizers with different frequencies and probe types were evaluated for the preparation of FLG. In each experiment, 1.5 kg of graphite slurry was treated using a cyclic ultrasonic system. The results demonstrated that the 25 kHz dumbbell probe produced the thinnest FLG with the lowest defect density. Moreover, applying a static pressure of 0.2 MPa in the cycle system enhanced the cavitation-induced exfoliation of graphite sheets, effectively reducing the layer count and distribution range of FLG. This method improves the conductivity while minimizing defect density.

Facile synthesis and electrochemical properties of sheet-rod-sheet structured NiCo2S4/EG/Ti3C2Tx nanocomposites

Electrode materials with outstanding stability and electrochemical activity are ideal for high-performance supercapacitors. Herein, we developed a simple two-step method for fabricating NiCo2S4/EG/Ti3C2Tx nanocomposites with a sheet(2D)-rod(1D)-sheet(2D) structure. The NiCo2S4 rods were embedded into the expanded graphite (EG) sheets via an in-situ hydrothermal method, then the Ti3C2Tx sheets were assembled with NiCo2S4/EG by an electrostatic self-assembly method. The obtained NiCo2S4/EG/Ti3C2Tx nanocomposites exhibited a synergistic effect among the components. The addition of EG inhibited the volumetric effect of NiCo2S4 during charging and discharging processes, while the high conductivity of Ti3C2Tx promoted charges transfer. The rod-like structure of NiCo2S4 effectively inhibited the self-stacking of Ti3C2Tx sheets. Consequently, the optimized composite exhibited an excellent specific capacitance of 1837.9 F·g−1 at a current density of 1 A·g−1. Additionally, the composite electrode exhibited a capacitance retention of 73.5 % during 10,000 charging-discharging cycles at a current density of 20 A·g−1.

Enhancing the electrochemical performance of graphite sheet electrodes for ketamine detection

Flexible graphite sheets (GS) have been a promising material for developing electrochemical sensors. In this work, we showed that the electrochemical activation protocol (+1.4 V followed by -1.0 V vs. Ag|AgCl|KCl(sat.) both at 200 s) in alkaline medium (0.5 mol l-1 NaOH) enhances the electrochemical activity of GS. Before the treatment, cyclic voltammetric profile of inner-sphere [Fe(CN)6]3-/4- redox couple at 50 mV s-1 exhibited an ill-defined voltammetric profile (ΔEp = 800 mV) while an increase in the reversibility was achieved (ΔEp = 225 mV) after the treatment. Additionally, the lower charge transfer resistance (Rct) measured by Electrochemical Impedance Spectroscopy (EIS) and a higher heterogeneous electron transfer constant (k0) corroborate with the enhancement in the electrochemical performance of treated GS electrodes. The SEM images revealed an irregular pattern with number of grooves, indicating a partially surface exfoliation and AFM analysis displayed an increase in the roughness. These findings agreed with the estimation of electroactive area which increased 3-times after the treatment. As proof of concept, ketamine (KET), an anesthetic often used as drug of abuse, was determined in synthetic saliva and veterinary pharmaceutical samples using treated GS electrodes and square wave voltammetric measurements. Linear range of 5.0–100.0 µmol l-1 with a limit of detection value of 2.1 µmol l-1 was obtained for KET. Appropriate recovery values (∼105 %) for the analysis of samples were achieved.

Metal-free ultrathin terahertz absorber with independently tunable dual narrow bands

Abstract A technique is introduced to precisely control the resonance behaviour of a metal-free graphene-based terahertz absorber by independently tuning dual resonant peaks. The proposed ultrathin absorber features a multilayer configuration, with two isolated resonator layers of patterned graphene on dielectric (SiO2) substrates, and a thin graphite sheet at the bottom serving as a reflector. The stacked arrangement enables independent tunability of the high-absorptivity resonant peaks at 7.33THz and 9.34THz. The structure, with a thickness of just λ/15 of the free-space wavelength, offers a compact design suitable for space-constrained applications. Its symmetrical geometry ensures polarization insensitivity and stable performance for incident angles up to 60°. Simulated results, analysed via CST Studio and validated with an Equivalent Circuit Model (ECM), demonstrate excellent thermal stability. Furthermore, the narrowband response of the proposed absorber improves its sensitivity for refractive index variations induced by biomolecular interactions validating its suitability in biosensing applications. The absorber demonstrates peak absorption across both the resonant frequencies with an analyte optimised at 1.5μm thickness. Sensitivity levels of 1.1THz/RIU and 1.05THz/RIU along with figure-of-merit (FOM) values of 2.11 and 2.23. are recorded for the lower and upper bands, respectively. The absorber offers enhanced selectivity owing to low values of full-width at half maximum (FWHM). High Q-factors of 12.85 and 19.3, confirm its strong potential for refractive index sensing. 

Revealing Energy Density in Porous Carbon Supercapacitors Using Hydroquinone Sulfonic Acid as Cathodic and Alizarin Red S as Anodic Redox Electrolytes.

Exploration of innovative strategies aiming to boost energy densities of supercapacitors without sacrificing the power density and long-term stability is of great importance. Herein, highly porous nitrogen-doped carbon spheres (NPCS) are decorated onto the graphite sheets (GSs) through a hydrothermal route, followed by a chemical activation. The capacitive performance of the NPCS is then enhanced by hydroquinone sulfonic acid (HSQA) incorporation in both cathodic electrolyte and electrode materials. Later, NPCS are decorated with polypyrrole (PPY), in which HSQA takes a versatile role as conjugated polymer dopant and cathodic redox additive. The capacitive performance of the negative electrodes is enhanced by incorporating of alizarin red S (ARS) as anodic redox additive. Finally, PPY(HQSA)@NPCS-GS//NPCS-GS asymmetric supercapacitor is assembled and tested in dual redox electrolyte system containing HQSA-cathodic and ARS-anodic electrolytes. This device delivers a remarkable energy density of 60.37 Wh kg-1, which is close or even better than lead acid batteries. Thus, the present work provides a novel pathway to develop high energy supercapacitors using redox active electrolytes for next-generation energy storage applications.

Orchestrating a Supercapacitive Symphony: Copper–Metal Organic Framework Integrated MXene Nanosheets on Graphite Sheet Electrodes Unveiling Its Synergistic Interactions by Density Functional Theory Study

Orchestrating a Supercapacitive Symphony: Copper–Metal Organic Framework Integrated MXene Nanosheets on Graphite Sheet Electrodes Unveiling Its Synergistic Interactions by Density Functional Theory Study

A novel engineered sandwich composite with ceramic-coated graphite fibre-reinforced face sheets and an auxetic core for enhanced broadband electromagnetic absorption: design using multiscale computational analysis

Abstract A novel sandwich composite is designed for enhanced broadband absorption using a multiscale computational analysis. The sandwich panel is configured with BaTiO3 coated graphite fiber reinforced polymer (C-GFRP) composite, while BaTiO3 based auxetic material is used as the core material. A computationally efficient in-house tool based on the variational asymptotic method is used to homogenise the electromagnetic properties and evaluate the reflection loss characteristics of the proposed sandwich structure using the scattering matrices. A detailed parametric study of 300 analyses is conducted to identify the optimal sandwich panel configurations for achieving broadband reflection loss under the normal incidence of transverse electric (TE) and transverse magnetic (TM) polarised waves. Two different configurations have been obtained, satisfying the requirements of broadband reflection loss in the X-band frequency range. Configuration (a) Vf = 15% without any ceramic coating, and configuration (b) Vf = 20% with ceramic coating volume fraction (Cf) of 70%. Configuration (a) and (b) maintained the desired reflection loss of greater than -10 dB up to an incidence angle of 40◦ and 60◦, respectively. With the demonstrated capability of covering the entire broadband frequency range, the proposed configurations can serve as baselines to explore novel ceramic-based engineered composite architectures for broadband absorption applications.

Fast preparing bioelectrode with conductive bioink for nitrite detection in high sensitivity and stability

Electrochemically active biofilms (EABs) for nitrite detection have high specificity, rapid response, operational simplicity, and extended lifespan advantages. However, their scale production remains challenging due to time-consuming and uniform preparation. In this study, a novel approach was proposed to fast fabricate an EAB biosensor with a synthetic biofilm electrode for nitrite detection. The biofilm electrode was prepared by coating bioinks with varying conductive materials onto the surface of the graphite sheets, showing short incubation time and good reproducibility. Incorporating conductive materials into the bioinks remarkably enhanced the maximum voltage of the first cycle of bioelectrode incubation, with an increase of up to 633% for carbon nanofibers. The nitrite reduction current was amplified by a factor of 2.97, due to the enhancement of extracellular electron transfer (EET). The developed nitrite biosensor exhibited a detection range of 0.1–15 mg NO2--N L−1, with a high sensitivity of 610.8 μA mM−1 cm−2, and a stabilization operation time of at least 280 cycles. This study not only provided valuable insights into conductive materials for synthetic biofilms but also presented a practical approach for the rapid preparation, scale production, and optimization of highly sensitive and stable EAB sensors.

Electrochemical measurements, structural and morphological studies of electrodeposited polypyrrole supercapacitor electrode

This study presented the electrochemical deposition of potassium nitrate-doped polypyrrole (Ppy:KNO3) on stainless steel (SS), graphite sheet (GRs), and carbon fiber (CF) substrates, Ppy:KNO3/SS, Ppy:KNO3/GRs, and Ppy:KNO3/CF supercapacitor electrodes. Structural, morphological, and molecular analyses were conducted using X-ray diffraction (XRD), scanning electronic microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). SEM images exhibited distinct morphologies of Ppy:KNO3 films, varying with cycles, scan rates, and Ppy:KNO3 concentrations. Ppy:KNO3/CF film displayed a unique structure with minimal particle aggregation. Electrochemical performance was assessed through Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) measurements and electrochemical impedance spectroscopy (EIS). Notably, Ppy:KNO3/CF demonstrated a specific capacitance of 1020 F/g at 1 A/g. It exhibited 92 % capacitance retention after 1000 cycles, along with impressive power and energy densities of 310 W/kg and 71.2 Wh/kg, respectively. These results represented a significant progress in the development of high-performance, durable supercapacitors.

Superior performance of asymmetric supercapacitor based on Cu doped bismuth ferrite electrode

Electrochemical energy storage devices, like supercapacitors and batteries, are needed to meet the constantly increasing demands of portable energy devices. Many types of supercapacitor electrodes were synthesized and reported which include carbon-based materials, polymers, oxides and perovskites. In this work, we report on the fabrication of Cu doped bismuth ferrite (Cu-BiFeO3, Cu-BFO) nanoparticles via sol-gel procedure. In most of the doping cases the costly rare earth elements like La, Nd, Sm, Ce and Yb are used to replace Bi. Electrodes of Bi1-xCuxFeO3 where x have the values 0.0, 0.025, 0.05, 0.075, 0.1 and 0.15 were deposited on graphitic sheets. Optimum Cu doping value was found to be at x = 0.05. Cu2+ ions doping in place of Bi3+ ions will reveal the roles of oxygen vacancies, as determined from XPS. The estimated values of specific capacitance was found to be 732 F/g at 0.5 A/g for the electrode at x = 0.05 in three electrode system. 5%Cu-BFO//Carbon black asymmetric supercapacitor (ASC) device can be charged and discharged reversibly at cell voltage of 0.0 up to 1.5 V when using a 0.5 M Na2SO4 aqueous electrolyte. This configuration allows the ASC device to deliver a great energy density of 37.25 Wh/kg at a power density of 752 W/kg. The ASC device demonstrates excellent cycling stability, retaining 88.64 % of its initial specific capacitance after 5000 cycles. Increasing the Cu content up to 15 % causes instability in the crystal structure of BFO resulting on phase segregation into Bi2Fe4O9 along with BFO and deterioration in the electrode overall performance. XPS showed that replacement of Cu2+ in place of Bi3+ disturbs the neutrality and the chemical environment of the compound. Hence to achieve neutrality and ionic balance, oxygen vacancies increase and the Fe2+/Fe3+ ratio increases as well. Both oxygen vacancies and the change in the Fe ions ratio reduce electrochemical impedance and give rise to charge density. The homogenous distribution of the pores at x = 0.05 contributed greatly to its fast electrolyte ion diffusion that improved the observed capacitive properties. One has to mention here, that despite doping that contains ions with different ionic size and/or different oxidation state is unfavorable, to some extent, due to the changes they produce in the electronic structure and the chemical environment, nevertheless it is sometimes beneficial in creating new parameters in the structure that promote specific application like in the case of the current work, oxygen vacancies, increase in surface area and the mixed state valency.

Design and performance assessment of a solar photovoltaic panel integrated with heat pipes and bio-based phase change material: A hybrid passive cooling strategy

This study investigates the effectiveness of an indirect passive cooling solution for photovoltaic (PV) panels using flattened heat pipes (FHPs) and phase change material (PCM). An innovative passive cooling design is proposed to cool a PV panel using multiple FHPs with a thin graphite sheet between the PV panel and the FHPs. Five experimental cases are examined under varying heat flux loads. Case O serves as the baseline with no cooling system, while Cases 1 to 4 feature different configurations of FHPs and aluminum sheets, with PCM heat sinks added in Cases 2 and 4. The investigation focuses on temperature profiles, temperature reductions, and final temperatures of the PV panel, especially at the end of a 4-hour experimental period when the PCM is fully melted. The results show significant temperature reductions in Case 1 compared to the baseline, with further improvement in Case 2 due to the PCM heat sink. Temperature reductions in Cases 2 and 4 are consistently higher than in Cases 1 and 3, demonstrating the enhanced cooling potential of PCM. Case 4 achieves the highest temperature reduction of 37.0 °C, followed by Case 2 with 34.9 °C under a radiative heat flux of 1000 W/m2. Using 4 FHPs (Cases 1 and 2) is economically justified, offering comparable cooling performance to 8 FHPs (Cases 3 and 4), thus ensuring cost-effectiveness and reducing material usage by over 50 %. A maximum enhancement in PV electrical efficiency of 17.3 % is achieved in Case 2 during PCM phase change with a radiative heat flux of 1000 W/m2.

Self-powered sensors utilizing single-pillar thermocells with pyrolytic graphite sheet electrodes: harvesting body heat and solar thermal energy

This study investigates the development of self-powered sensors employing single-pillar thermocells to harness body heat and solar thermal energy. A pyrolytic graphite sheet was selected for its low water vapor permeability, and its surface was modified to be hydrophilic to minimize interfacial resistance. Two types of DC–DC converters, Asahi Kasei Microdevices AP4473 and matrix mercury, underwent evaluation for compatibility with these thermocells. The compact 1.5 cm3 (1 cm × 1 cm × 1.5 cm) device effectively powered the AP4473 converter, illuminating a light-emitting diode. A larger device (2.5 cm × 2.5 cm × 1.5 cm) efficiently drove the matrix mercury converter, enabling the operation of bluetooth low-power sensors. These self-powered sensors wirelessly provided humidity and temperature data using solar thermal energy for approximately 4 h per day during peak temperature differences in January. This study showcases the potential of thermocells for sustainable energy harvesting and suggests avenues for future research, such as exploring alternative heat sources like geothermal energy to power these sensors.

Degradation of 2,4-dinitrotoluene from aqueous solutions by three-dimensional electro-Fenton with magnetic activated carbon particle electrodes (GAC/Fe3O4)

Abstract 2,4-Dinitrotoluene (2,4-DNT) is a broadly applied nitroaromatic compound with multiple applications, and its simple production has resulted in its extensive utilization in producing explosives, dyes, and rubber. This substance is hazardous and induces genetic mutations in humans, fish, and microorganisms. Thus, this research was done to assess the effectiveness of the three-dimensional electro-Fenton (3D/EF) process employing magnetic activated carbon particle electrodes (GAC/Fe3O4) in eliminating 2,4-dinitrotoluene from water-based solutions. In this experimental investigation, Fe3O4 nanoparticles were created using the chemical co-precipitation technique. The G/β-PbO2 anode was fabricated by electrochemically depositing PbO2 layers on graphite sheets. G/β-PbO2 and stainless steel were utilized as the anode and cathode, respectively. The structure, particle size, and properties of the GAC/Fe3O4 nanocomposite were analyzed using FESEM, XRD, and EDX. The morphology of the G/β-PbO2 electrode was also examined using SEM. The Taguchi experimental design method was employed to identify the optimal conditions. The outcomes demonstrated that higher reaction time and current density, as well as lower pH and pollutant concentration, resulted in improved 3D/EF efficiency. Accordingly, the optimum values of parmeters were identified to be a concentration of 2,4-DNT = 50 mg/L, pH = 3, electrolysis time = 100 min, and current density = 8 mA/cm2. With these parameters, the degradation efficiency of 2,4-DNT through the examined system was 98.42 %, alongside removal efficiencies of 84.69 % for COD and 79.67 % for TOC. Additionally, the results indicated an increase in the average oxidation state (AOS) (from 1.27 to 1.95) and carbon oxidation state (COS) (from 1.27 to 2.75) in the 3D/EF process, along with a decrease in the COD/TOC ratio (from 1.81 to 1.36), indicating the effectiveness of the 3D/EF system in enhancing the biodegradability of 2,4-DNT. Overall, the combined 3D/EF process with a G/β-PbO2 anode has relatively high efficiency in degrading solutions containing DNT and can be considered a viable treatment option for wastewater containing substances such as 2,4-DNT.

Investigation of simultaneous production of H2 and separable carbon from CH4 in a fluidised bed of NiO/Ca2Fe2O5/CaO particles

This work investigated the possibility of simultaneous production of hydrogen/syngas and separable solid carbon in a fluidised bed by using CH4-CO2 cycles and exploring the carbon growth over solid catalytic particles of NiO/Ca2Fe2O5/CaO. This two-stage process included i) stage I: H2-rich gas and carbon were simultaneously generated from the interaction between CH4 and NiO/Ca2Fe2O5/CaO particles; and ii) stage II: the reduced/carbon-deposited particles were regenerated in CO2. Following our previous successful demonstration of the process for stable hydrogen production over cycles, this study focused on the formation of solid carbon and aimed at understanding its growth mechanism as well as demonstrating the potential of using fluidisation as a means of automatic carbon separation. By tracking the carbon growth history and the change in phases of the reacted NiO/Ca2Fe2O5/CaO particles at temperatures from 700 to 900 °C, we discovered the formation of various forms of nano-structured carbon from CH4 conversion (e.g. partial oxidation, pyrolysis). These include carbon nanotubes (CNTs), carbon graphite sheets, carbon onions (CNOs), and carbon fibres. Amorphous carbon was also observed, particularly in the initial stage of CH4 conversion. Higher temperatures like 800 °C and 900 °C gave faster kinetics of CH4 conversion and more formation of solid carbon. Fe3C phase was observed on the reduced catalytic particles and could act as an intermediate phase or carbon sink for carbon growth. The results suggested that other mechanisms for carbon deposition, such as directly over Fe sites, may also exist. Fluidisation with a higher U/Umf ratio separated more carbon-rich fines from the bulk catalytic particles in the fluidised bed. Fluidising with air at 700 °C effectively removed amorphous carbon on the reacted catalytic particles, whilst structured carbon remained. Full separation and purification to obtain pure carbon require furthers optimisation of e.g. fluidisation parameters and material design.