Co-doped Composites Research Articles

Preparation of N, S co-doped carbon nanotubes composites by coal pyrolysis for the CO2 capture

In this paper, nitrogen and sulfur co-doped carbon nanotubes composites were prepared by coal pyrolysis with the aim of applying them to carbon dioxide adsorption. Compared with previous carbon nanotubes modification methods, this study increased the specific surface area, microporosity and the number of adsorption sites of the materials through structural modification and surface modification, thus improving the adsorption capacity. Notably, secondary KOH activation modification was employed to increase the N and S elemental content in the adsorbent. Without leading to the loss of specific surface area, the specific surface area after modification was increased by 29 % to 1875 m2/g, and the N content in the adsorbent could be reasonably regulated. The IAST calculations revealed that the prepared adsorbent had a high selectivity for CO2/N2 in binary gas mixtures, which is of practical significance for the treatment of flue gas streams. In addition, the isocratic heat of adsorption of the adsorbent was calculated to be less than 40 kJ/mol using the Clasius-Clapeyron equation, which indicates that the adsorbent is easy to desorb and can be used several times. After five consecutive CO2 adsorption experiments, the adsorbent retained 98.22 % of its CO2 adsorption capacity. Overall, this study not only provides a new idea for the high value-added utilization of low-rank bituminous coal. It also provides an important reference for the large-scale doping of N and S elements in coal-based carbon materials, which has certain theoretical and applied values.

Improved photocatalytic activation of PMS using Co-doped g-C3N4 composites for effective degradation of tetracycline: Catalyst performance, photogenerated carrier transfer and degradation mechanism

Photocatalytic coupled SO4•- based advanced oxidation processes (SR-AOPs) are considered as an advanced wastewater treatment technology for degrading pollutants. In this work, Co-doped g-C3N4 (CCN) photocatalysts were successfully designed for activation of permonosulfate (PMS) under visible light to efficiently degrade tetracycline (TC). The CCN photocatalyst exhibited enhanced degradation efficiency, removing 95.9 % of TC within 20 min, with a much higher degradation rate constant (0.1354 min-1) than that of the photocatalytic system (0.0090 min-1) and the SR-AOPs system (0.0538 min-1). The separation and transport properties of photogenerated carriers were probed with the assistance of measurements including surface photovoltage and photoluminescence. The results showed that the introduction of Co promoted the effective separation of photogenerated charges in CCN, which accelerated the Co3+/2+ cycle and realized the efficient activation of PMS. Overall, this study provides a new strategy for the development of efficient photocatalytic activation of PMS for rapid degradation of organic pollutants.

Electrical surface breakdown characteristics of micro- and nano-Al2O3 particle co-doped epoxy composites

Abstract Epoxy microcomposites are basic materials for gas-insulated switchgear (GIS) spacers that are subjected to huge electrical stress. Previous works have indicated that nanoparticles are beneficial to dielectric performance. However, surface electrical breakdown, a typical fault in GIS of co-doped micro- and nanoparticles in epoxy composites, is seldom studied. In this work, numerous concentrations of micro- and nano-Al2O3 are co-doped into an epoxy matrix; the surface traps, surface charging, and surface breakdown voltages (V sb) of the co-doped composites are studied, and the influence of micro- and nano-Al2O3 on the electrical surface breakdown is clarified. The results show that V sb first decreases and then increases with the microparticles, and V sb decreases from 25.34 kV to 19.52 kV. As the number of nanoparticles increases, V sb increases and then decreases when the microparticle loading is low, but decreases and then increases when the microparticle loading exceeds 40 wt%. Micro-Al2O3 particles introduce surface shallow traps into epoxy composites, while small amounts of nano-Al2O3 introduce deep traps. Two different mechanisms dominate the surface charging and V sb of epoxy micro-nanocomposites. When the surface conductivity is lower than 7 × 10−14 S, the surface charges are reduced by the suppression of electrode injection as the trap depth increases, and V sb increases. When the surface conductivity exceeds 7 × 10−14 S, the surface charge dissipation rate increases with the surface conductivity and V sb increases as the surface conductivity increases. Our work indicates that co-doped micro- and nano-particles should keep the surface conductivity away from the specic value (7 × 10−14 S) to safeguard insulation properties for GIS spacers.

Co-doped polyaniline composites for biological application: Morphological, functional, optical and antibacterial activities

In the present work, we have successfully synthesized co-doped polyaniline (PANI) composites with various organic acids DBSA, phthalic acid, oxalic acid and Calotropis proceralatex using a simple chemical oxidative polymerization method. The structural, optical, surface morphology and antibacterial analyses were carried out for the synthesized PANI (DBSA-Phthalic acid), PANI (DBSA-Oxalic acid) and PANI (DBSA-C.Procera latex) composites. The structural characterization using XRD and FT-IR measurements confirmed the formation of emeraldine salt form of PANI from the observed characteristic peaks of PANI in all the composites. The observed UV–visible absorption and PL emission peaks also assured the synthesis of PANI in emeraldine form. SEM micrographs of PANI (DBSA-phthalic acid) composites exhibited continuous rock-like agglomerated structure. The antibacterial activity tested against medically important bacteria Bacillus subtilisrevealed a maximum inhibition zone for the DBSA-phthalic acid doped PANI composites when compared with other composites. The average value of zone of inhibition for the PANI composites is found to be 21–24 nm. The minimum inhibitory concentration (MIC) is found to be 1 mg/L for all the PANI composites whereas the minimum bactericidal concentration (MBC) is found to be 60 mg/L for PANI (DBSA-Phthalic acid) and 80 mg/L for PANI (DBSA-Oxalic acid), PANI (DBSA-C.Procera latex) composites. A larger and clear zone of inhibition exhibited by the synthesized co-doped PANI composites confirms their potential as an effective antibacterial agent.

Metal–organic framework derivatives with gradient structures via multidimensional assembly engineering for tunable efficient microwave absorption

Multidimensional assembly strategy facilitates the preparation of MOF-derived Co-doped carbon-based composites assembled with 1D nanowires/rods and 0D nanobubbles to enhance and optimize microwave attenuation.

Nitrogen and sulphur co-doped carbon-based composites as electrocatalysts for the anion-exchange membrane fuel cell cathode

Nitrogen and sulphur co-doped nanocarbon composites based on silicon carbide-derived carbon (SiCDC), carbon nanotubes (CNT) and/or mesoporous carbon (MPC) are prepared for oxygen reduction reaction (ORR) and anion-exchange membrane fuel cell (AEMFC) studies. Thiosemicarbazide is used as nitrogen and sulphur doping agent. The rotating ring-disc electrode (RRDE) measurements exhibit good electrocatalytic activity towards the ORR for all the prepared catalysts in alkaline solution. Obtained materials are rich in pyridinic-N and consist of thiophene-S, which could improve the ORR performance due to the synergistic effect of N and S. Textural properties, including specific surface area (SSA) and porosity parameters are different amongst the three studied N,S-doped nanocomposite materials, which also affect the outcome of AEMFC test results. In AEMFC testing using Aemion+ (AF2-HLE8-10-X, 10 μm) anion-exchange membrane, N,S-SiCDC/MPC (with SSAdft = 952 m2 g−1) shows the highest performance with the peak power density (Pmax) of 379 mW cm–2. This result is comparable with the performance of Pt/C catalyst in AEMFC (Pmax = 347 mW cm–2), making N,S-doped nanocomposite materials promising cathode catalyst for AEMFCs.

MOC Composites for Construction: Improvement in Water Resistance by Addition of Nanodopants and Polyphenol.

The topic of modification of magnesium oxychloride cement (MOC) using specific functional additives is very much pronounced in the research of alternative building materials. This study deals with the co-doping of MOC by 1D and 2D carbon nanomaterials in order to improve its mechanical properties while using tannic acid (TA) as a surfactant. Furthermore, the effect of TA on MOC also improves its water resistance. As a filler, three size fractions of standard quartz sand are used. The proposed types of MOC-based composites show promising results considering their mechanical, macro- and microstructural, chemical, and hygric properties. The use of 1D and 2D nanoadditives and their mixture enables the improvement in the flexural strength and particularly the softening coefficient, which is the durability parameter characterizing the resistance of the prepared materials to water. After immersion in water for 24 h, the compressive strength of all tested specimens of modified composites was higher than that of the reference composite. Quantitatively, the developed co-doped composites show mechanical parameters comparable to or even better than those of commonly used Portland cement-based materials while maintaining high environmental efficiency. This indicates their potential use as an environmentally friendly alternative to Portland cement-based products.

Exploring synergistic sintering factors and nanopore regeneration of calcium-based thermochemical energy storage materials

Calcium-based thermochemical energy storage is essential for high-temperature solar energy utilization. However, performance decay is inevitable in repeated calcination/carbonation cycles, even for modified materials. In this study, the effects of synergistic sintering factors on performance decay are investigated, including chemical reaction, temperature and CO2 atmosphere. More importantly, rather than complicating the initial preparation process of the anti-sintering composites to achieve higher stability, a regeneration method is proposed to repair the nanopores of sintered composites and recover their performances. After using citric acid to dissolve materials with heavily sintered morphologies and reconstruct their porous structures, the energy storage densities of both the co-doped and benchmark materials increase by 2–4 times. The regenerated Al/Mg co-doped composite also shows high cyclic stability in subsequent long-term cycles. Furthermore, DFT calculations illustrate the strong atomic interaction between CaO and dopants. The economic analysis reveals that the regeneration costs of the co-doped composites are approximately one-half of their synthesis costs, making them a cost-efficient choice for long-term industrial application. This work expands the limited perspectives of current modification research on improving cyclic stability. It can guide the actual industrial applications of thermochemical energy storage, thus enhancing material reutilization and realizing costs reduction.

Amino-functionalization-assisted construction of CoP/N, P co-doped graphene to enhance stable lithium storage via electrostatic interaction and strong bonds

Compounding CoP nanoparticles with graphene can serve as promising anode materials for high-performance lithium-ion batteries. However, the weak binding and dispersion between CoP and graphene usually lead to poor structural stability limiting the lithium storage performance. Herein, an amino-functionalization-assisted one pot self-assembly method is employed to synthesize CoP/nitrogen, phosphorus co-doped graphene composites (CoP/NPG) with a highly stable 3D porous structure. The negatively charged phytic acid can act as a bridging connection between the positively charged amino-functionalized graphene and Co2+ by strong electrostatic attraction, ensuring the synthesized CoP nanoparticles are uniformly distributed on NPG sheets with high conductivity and plenty of active centers. Meanwhile, establishing strong C–P and Co–O–C surface chemical bonds between CoP and NPG improves the structural strength and promotes fast electron/ion transport, which effectively alleviates the volume expansion of CoP. Benefiting from these advantages, the CoP/NPG electrode displays high lithium storage capacity (917.9 mAh g − 1 at 0.5 A g − 1 after 600 cycles), ultra-long cyclic stability (434.8 and 350.5 mAh g − 1 at 3.0 and 5.0 A g − 1 after 3000 cycles) and fast pseudocapacitive charge storage (contribution even up to 97% at 2.0 mV s − 1). This strategy offers promising prospects for the preparation of highly stable anode materials.

Directionally Solidified Cobalt-Doped MgO-MgAl2O4 Eutectic Composites for Selective Emitters

Cobalt-doped MgO-MgAl2O4 eutectic composites were explored for their use as selective emitters for thermophotovoltaic devices. Eutectic ceramic rods with different cobalt content were directionally solidified by using the laser floating zone technique at two processing rates to obtain microstructures with different domain sizes. Thermal emission between 1000 °C and 1500 °C and optical properties (reflectance and transmittance) at room temperature were measured in the Co-doped composites and the effect on microstructure and cobalt content was investigated. Thermal emission consisted of an intense broad band at about 1.67 µm matching with the bandgap of the InGaAs cell. The emission was ascribed to the de-excitation from the 4T1(F) multiplet to the 4A2(F) ground state of the thermally excited Co ions located in the tetrahedral sites of the MgAl2O4 phase. The selectivity of the thermal emission showed a decrease with the cobalt content due to the enhancement of other electronic transitions, which leads to keeping the cobalt content in these composites at low levels (<0.15% at Co) for their use as selective emitters.

Near-infrared rechargeable glass-based composites for green persistent luminescence

The fabrication of Yb3+, Tm3+ co-doped oxyfluorophosphate glass-based composites, with green persistent luminescence after being charged with near-infrared light, is demonstrated. The mechanism responsible for the green afterglow after near-infrared illumination is unveiled. The composite is prepared using a modified melting process to limit the evaporation of fluorine during melting. Intense (blue and ultraviolet) up-conversion emission is obtained by optimizing the Yb2O3 and Tm2O3 concentrations. A heat treatment promotes volume precipitation of Yb3+, Tm3+ co-doped CaF2 crystals. Although the intensity of the blue up-conversion emission from the Tm3+1G4 level is lower in the highly Yb3+-concentrated glass-ceramic due to reverse energy transfer from Tm3+ to Yb3+, the heat treatment leads to an increase of the intensity of the emissions around 346 nm, 361 nm nm and 450 nm coming from the Tm3+1I6 and 1D2 levels. By combining the Yb3+ and Tm3+ ions with SrAl2O4:Eu2+,Dy3+crystals, green afterglow can be obtained after charging with near-infrared light.

NiO/nitrogen-oxygen co-doped carbon nanoflower composites based on covalent organic frameworks for lithium-ion battery anodes

Designing novel NiO/porous carbon nanocomposites is an effective strategy to improve poor conductivity and rapid capacity fading of NiO in lithium-ion batteries (LIBs). Covalent organic frameworks (COFs) are attractive materials for LIBs as they have large specific surface areas, well-ordered structure, and controllable pore size. Here, we designed a COFTpPa nanoflower as templates for the preparation of porous carbon and a carrier for NiO to obtain NiO/nitrogen-oxygen co-doped carbon nanoflower (NiO/NCF) composites. NiO nanostructures have a smaller volume effect, and the coating of carbon nanoflowers can further buffer the volume expansion of NiO nanostructures, which effectively slow down the capacity decay. In addition, the NCF derived from COFTpPa provide a larger specific surface area and more pores, which not only increases the capacity of nanocomposites but also improves the electrical conductivity of the electrodes. When applied to the anode of LIBs, NCF and NiO/NCF exhibit excellent performance (with first-cycle capacities of 1038.2 and 1685.9 mAh g−1, respectively, and high first coulomb efficiencies of 61.5 % and 60.9 %, respectively). The designed NiO/NCF nanocomposites is a promising anode material for LIBs.

Improved durability in thermochemical energy storage using Ti/Al/Mg Co-doped Calcium-based composites with hierarchical Meso/Micro pore structures

Calcium-based thermochemical energy storage is promising for high-temperature thermal utilization of the solar energy. However, the energy storage performances of calcium-based materials show sintering-induced decays after multiple cycles. Here, the co-doped CaO composites that are rich in mesopores and micropores are synthesized by a modified sol–gel method, where MgCl2 is the primary dopant, and tetrabutyl titanate or aluminum nitrate is used as an auxiliary dopant. The decomposition of MgCl2 into MgO leads to the formation of thin shell structures around the composites, which is further stabilized by the generated calcium titanate or calcium aluminate, as they work synergistically to improve the long-term cyclic stabilities. The conversions in CaO and cyclic stabilities of the co-doped composites are remarkable, higher than most of the existing composites. Their average energy storage densities exceed 1132 kJ kg−1 over 100 calcination/carbonation cycles and more than 75% of CaO still maintains reactivity after 100 cycles. Their porous thin-shell and interconnected network structures provide ample space for reaction, and the particle sizes are also uniform with relatively lower particle growth, which reflect the high anti-sintering feature. The CaO-based composite chemistry and synthesis methods developed here show great promises for their long-term industrial applications in concentrated solar energy storage.

Synthesis of bristlegrass-like Co-doped Ni2P composites on Ni foam for overall seawater splitting

Seawater is the most abundant resource on earth, so developing cost-effective, highly durable corrosion resistance and efficient electrocatalysts are crucial to enhance seawater splitting. Herein, we prepared 3D bristlegrass-like Co-doped Ni2P (Co-Ni2P) composites supported on Ni foam (NF) through a facile solvothermal method combined and a subsequent phosphatization treatment. Benefiting from the unique structure, Co-Ni2P shows excellent electrocatalytic activity as an electrode material for both the hydrogen evolution reaction (HER, low overpotential of 116 mV at 50 mA cm−2) and oxygen evolution reaction (OER, low overpotential of 266 mV at 50 mA cm−2). Moreover, the as-prepared Co-Ni2P composites exhibit excellent stability and corrosion resistance in an alkaline medium. Density functional theory (DFT) calculations were employed to evaluate the H∗ adsorption of Co-Ni2P, and the results proved the high catalytic activity for the HER. This study provides new materials with a unique morphology for overall water splitting.

One-Step Calcination Process for the Construction of Oxygen Deficient Fe2O3/N, P Co-doped Carbon Composites for High-Performance Supercapacitors

One-Step Calcination Process for the Construction of Oxygen Deficient Fe2O3/N, P Co-doped Carbon Composites for High-Performance Supercapacitors

Co-Doped Magnesium Oxychloride Composites with Unique Flexural Strength for Construction Use.

In this study, the combined effect of graphene oxide (GO) and oxidized multi-walled carbon nanotubes (OMWCNTs) on material properties of the magnesium oxychloride (MOC) phase 5 was analyzed. The selected carbon-based nanoadditives were used in small content in order to obtain higher values of mechanical parameters and higher water resistance while maintaining acceptable price of the final composites. Two sets of samples containing either 0.1 wt. % or 0.2 wt. % of both nanoadditives were prepared, in addition to a set of reference samples without additives. Samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and energy dispersive spectroscopy, which were used to obtain the basic information on the phase and chemical composition, as well as the microstructure and morphology. Basic macro- and micro-structural parameters were studied in order to determine the effect of the nanoadditives on the open porosity, bulk and specific density. In addition, the mechanical, hygric and thermal parameters of the prepared nano-doped composites were acquired and compared to the reference sample. An enhancement of all the mentioned types of parameters was observed. This can be assigned to the drop in porosity when GO and OMWCNTs were used. This research shows a pathway of increasing the water resistance of MOC-based composites, which is an important step in the development of the new generation of construction materials.

Nio/Nitrogen-Oxygen Co-Doped Carbon Nanoflower Composites Based on Covalent Organic Frameworks for Lithium-Ion Battery Anodes

Nio/Nitrogen-Oxygen Co-Doped Carbon Nanoflower Composites Based on Covalent Organic Frameworks for Lithium-Ion Battery Anodes

Facile Oxygen-promoted Synthesis of Cu, N Co-doped Carbon Composites for Oxygen Reduction

Facile Oxygen-promoted Synthesis of Cu, N Co-doped Carbon Composites for Oxygen Reduction

Environmentally friendly bark-derived Co-Doped porous carbon composites for microwave absorption

Biomass-derived porous carbon has attracted tremendous attention in many research fields due to its cheap and feasible strategy. In this work, bark-derived Co-doped porous carbon composites (Co@PC) for microwave absorption (MA) applications were successfully prepared through a simple method. The minimum reflection loss (RLmin) of Co@PC (carbonized at 800 °C, Co2+ concentration is 0.15 molL-1) is −49.2 dB at 10 GHz and a wide effective absorption bandwidth (EAB) of 6.16 GHz was obtained. Further, by adjusting carbonization temperature of the bark, the MA performance could be further enhanced. The results show that the RLmin could be −58.4 dB at 8.6 GHz when the bark was carbonized at 900 °C. The retained channel structures of the bark played an important role in this excellent MA performance, which is not only cause multiple reflections and scattering of microwaves, but also benefit to the impedance matching. Cobalt-nanoparticles (Co-NPs) dispersed on the surface of the channel structures, endow a strong magnetic loss of microwave energies. In addition, radar cross section (RCS) simulation results also demonstrate that Co@PC can be applied in the field of microwave absorbing materials (MAMs).

Metal heteroatom (Mg, Cu and Co) and porous carbon co-doped MIL-101 composites with superior acetone capture capacity

The development of highly active and stable adsorbents for volatile organic compounds (VOCs) capture is an efficient solution to address global problems in atmospheric pollution and environmental health. Herein, a metal–organic framework derived adsorbent consisting of metal heteroatom (Mg, Cu and Co) and porous carbon supported on MIL-101 framework is designed to enable high affinity for adsorbing acetone. The doped metal heteroatoms are homogeneously dispersed in the MIL-101/PC octahedron. The modification of doped metal heteroatoms improves the acetone adsorption capacity of the MIL-101/PC composite at low relative pressure. Importantly, the optimized 20%Mg@MIL-101/PC composite not only shows higher surface area (3838 m2 g−1) and pore volume (2.24 mL g−1) than MIL-101/PC, but also creates stronger active adsorption sites for acetone. As a consequence, the acetone adsorption capacity of 20%Mg@MIL-101/PC reaches 1309 mg g−1 at 288 K and 18 bar, and the saturated adsorption capacity decreases by only 12% over 10 adsorption–desorption consecutive cycles. Consequently, quantum chemistry calculation method is performed to better understand the microscopic adsorption behavior of acetone. The results of density functional theory (DFT) calculation show that the introduction of Mg can significantly improve the dipole moment of MIL-101 core and reduce its gap band energy, thus enhancing the electrostatic interaction with acetone molecule.