Dual biomass-derived porous carbon heterogeneous functionalized mesoporous CuCo2O4 nanocomposite combined with molecularly imprinted polymers as an electrochemical sensing platform for hypersensitive and selective determination of dimetridazole contaminants

In this study, an original molecularly imprinted electrochemical sensor (MIECS) is prepared using layer-by-layer modification of sensitization nanomaterials (CuCo2O4/BPC-E) coupled with molecularly imprinted polymers (MIPs) for the ultrasensitive and rapid determination of dimetridazole (DMZ) contaminants. The biomass waste of eggshell (ES) powders subtly introduced in situ in the carbonization process of psyllium husk (PSH) substantially promotes the physicochemical properties of the resulting biomass-derived porous carbon (BPC-E). The large specific surface area and abundant pores provide a favourable surface for loading mesoporous CuCo2O4 with a spinel structure. The assembly of CuCo2O4/BPC-E on the gold electrode (GE) surface enhances the electrochemical sensing signal. The MIPs constructed using DMZ and o-phenylenediamine (oPD) as templates and functional monomers boost the targeted recognition performance of the analyte. The combined DMZ targets then undergo an electrochemical reduction reaction in situ with the transfer of four electrons and four protons. Under optimum conditions, the current response of differential pulse voltammetry (DPV) exhibits two linear ranges for DMZ detection, 0.01-10 μM and 10-200 μM. The limit of detection (LOD) is 1.8 nM (S/N = 3) with a sensitivity of 5.724 μA μM-1 cm-2. The obtained MIECS exhibits excellent selectivity, reproducibility, repeatability and stability. This electrochemical sensing system is applied to the detection of real samples (tap water, coarse fodder and swine urine), yielding satisfactory recoveries (90.6%-98.1 %), which are consistent with those obtained via HPLC. This finding verifies that the utility of MIECS for monitoring pharmaceutical and environmental contaminants and ensuring food safety.

Active nitrogen sites on nitrogen doped carbon for highly efficient associative ammonia decomposition

Nitrogen doped carbon materials have been studied as catalyst support for ammonia decomposition. There are 4 different types of nitrogen environments (graphitic, pyrrolic, pyridinic and nitrogen oxide) on the amorphous support identified. In this paper, we report a 5%Ru on MgCO3 pre-treated nitrogen doped carbon catalyst with high content of edge nitrogen-containing sites which displays an ammonia conversion rate of over 90% at 500°C and WHSV = 30,000 mL gcat -1 h-1. It also gives an impressive hydrogen production rate of 31.3 mmol/(min gcat) with low apparent activation energy of 43 kJ mol-1. Fundamental studies indicate that the distinct average Ru-N4 coordination site on edge regions is responsible for such high catalytic activity. Ammonia is stepwise decomposed via a Ru-N(H)-N(H)-Ru intermediate. This associative mechanism circumvents the direct cleavage of energetic surface nitrogen from metal to form N2 hence lowering the activation barrier for the decomposition over this catalyst.

Synthesis of graphitized hierarchical porous carbon supported transition-metal for electrochemical conversion

Carbon materials supported metal with high graphitization and hierarchical pore structure are emerging as promising catalysts in electrochemical conversion areas. However, a facile method to prepare this class of catalysts...

Fabrication of porous carbon derived from cotton/polyester waste mixed with oyster shells: Pore-forming process and application for tetracycline removal

Porous carbon was fabricated from cotton/polyester-based textile wastes as a carbon source coupled with oyster shells for tetracycline removal. The preparation conditions were optimized and detailed characterization was conducted to study the effects of oyster shells on cotton/polyester pyrolysis. The optimal pyrolysis temperature (900 °C), pyrolysis time (1 h) and mass ratio (OS/CPW of 1:1) were determined using the Box-Behnken experiment. The best porous carbon reached a surface area of 645.05 m²/g. Oyster shells acted as templates to produce cotton/polyester-based porous carbon and a possible pore-forming process was proposed. CaO was converted from CaCO₃, which played the dominant role in developing the mesoporous structure. CO₂ gas released from CaCO₃ promoted the creation of micropore structure. In addition, the impurites of oyster shells acted as the dispersing agent inhibiting CaCO₃ and CaO aggregation and growth. Fe₂O₃ and K₂O from impurities reacted with the carbon skeleton to increase microporosity. Finally, the well-developed and uniform porous carbon was obtained. The first-pseudo order model and Langmuir isotherms were suitable. The maximum adsorption capacity of PC-OS-900 was 515.17 mg/g which competed with other waste-based adsorbents. The TET adsorption mechanism was related to pore distribution, hydrogen bonds, π-π EDA interactions and electrostatic interactions.

A cobalt-pyrrole coordination compound as high performance cathode catalyst for direct borohydride fuel cells

Pyrrole and cobalt nitrate were used as nitrogen and metal sources respectively to synthesize a dinitratobis(polypyrrole)cobalt(ii) (Co(polypyrrole)₂(NO₃)₂) adduct as the precursor of a Co–pyrrole/MPC catalyst. Pyrrole has the capability of polymerization and coordination with Co(ii). Taking this advantage, the Co(polypyrrole)₂(NO₃)₂ coordination can form a long-chain structure with abundant and robust Co–N bonds, contributing to significantly increased catalytic sites in the product catalyst. As a result, the obtained Co–pyrrole/MPC (MPC = macroporous carbon) catalyst exhibited high ORR catalytic activity in alkaline media and excellent performance in direct borohydride fuel cell (DBFC). A peak power density up to 325 mW cm⁻² was achieved at ambient condition, outperforming the commercialized Pt/XC-72 benchmark containing 28.6 wt% Pt. The construction of long-chain coordination precursor was verified playing a key role in the electrochemical improvement of Co–pyrrole/MPC catalyst in DBFC.

Co–pyrrole/MPC was synthesized by using pyrrole and cobalt nitrate as nitrogen and metal source, which enabled a higher peak power density than the commercialized 28.6 wt% Pt/XC72 in DBFC.

Constructing Hierarchical Porous Carbons With Interconnected Micro-mesopores for Enhanced CO2 Adsorption

A high cost-performance carbon dioxide sorbent based on hierarchical porous carbons (HPCs) was easily prepared by carbonization of raw sugar using commercially available nano-CaCO3 as a double-acting template. The effects of the initial composition and carbonization temperature on the micro-mesoporous structure and adsorption performance were examined. Also, the importance of post-activation behavior in the development of micropores and synthesis route for the formation of the interconnected micro-mesoporous structure were investigated. The results revealed excellent carbon dioxide uptake reaching up 2.84 mmol/g (25oC, 1 bar), with micropore surface area of 786 m2/g, micropore volume of 0.320 cm3/g and mesopore volume of 0.233 cm3/g. We found that high carbon dioxide uptake was ascribed to the developed micropores and interconnected micro-mesoporous structure. As an expectation, the optimized HPCs offers a promising new support for the high selective capture of carbon dioxide in the future.

Ultrasound-assisted dispersive solid phase nanoextraction of selected personal care products in wastewater followed by their determination using high performance liquid chromatography-diode array detector

This study reports a rapid and simple method based on ultrasound-assisted dispersive solid phase nanoextraction (UA-SPNE) method for the extraction and preconcentration of selected personal care products using MPC@Al₂O₃-SiO₂ nano adsorbent. A high performance liquid chromatograph equipped with a diode array detector (HPLC-DAD) was used to detect the analytes of interest. Experimental parameters affecting the extraction and preconcentration efficiency of the UA-SPNE (such as mass of adsorbent, extraction time, sample pH and eluent volume,) were optimized using fractional factorial design and response surface methodology based on central composite design. Under optimized conditions, the linear range for benzophenone, N,N-diethyl-3-methylbenzamide and trichlorocarbanilide were in the interval of LOQ-1000 μg L^-1 with correlation coefficients ranged from 0.9907 to 0.9977. The limits of detection and limits of quantification were 0.066-0.096 μg L^-1 and 0.22-0.32 μg L^-1, respectively. The accuracy of the UA-SPNE/HPLC-DAD method was evaluated using spike recovery test and the recoveries were in the range of 98-107%. The repeatability and reproducibility of the method 0.8-1.0 % and 2.4-4.4%, respectively.

In situ template synthesis of hierarchical porous carbon used for high performance lithium-sulfur batteries

Hierarchical porous carbon (HPC) consists of micropores, mesopores and macrospores which are synthesized by in situ formation of template followed by acid etching. The obtained pores are three-dimensional and interconnected, and evenly distributed in the carbon matrix. By adjusting the ratio of the raw materials, the high specific surface area and large pore volume is afforded. The obtained HPC-3 samples possess graphite flakes and locally graphited-carbon walls, which provide good electrical conductivity. These unique characteristics make these materials suitable cathode scaffolds for Li-S batteries. After encapsulating 61% sulfur into HPC-3 host, the S/HPC-3 composite exhibits excellent cycling stability, high columbic efficiency, and superior rate cycling as a cathode material. The S/HPC-3 composite cathode displays an initial discharge capacity of 1059 mA h g-1, and a reversible capacity of 797 mA h g-1 after 200 cycles at 0.2C. The discharge capacities of the S/HPC-3 composite cathode after every 10 cycles at 0.1, 0.2, 0.5, 1, and 2C are 1119, 1056, 982, 921, and 829 mA h g-1, respectively.

Prevention of active-site destruction during the synthesis of high performance non-Pt cathode catalyst for fuel cells

Active-site destruction caused by CO₂ attack and thermal decomposition leads to catalyst deterioration toward oxygen reduction reaction.

Synthesis of sustainable lignin-derived mesoporous carbon for supercapacitors using a nano-sized MgO template coupled with Pluronic F127

Sustainable lignin-derived mesoporous carbon for supercapacitors by simultaneously employing MgO nanoparticles and Pluronic F127 as templates.

CoP Nanoparticles in Situ Grown in Three-Dimensional Hierarchical Nanoporous Carbons as Superior Electrocatalysts for Hydrogen Evolution

The development of efficient and low-cost hydrogen evolution reaction (HER) catalysts is critical for storing energy in hydrogen via water splitting but still presents great challenges. Herein, we report synthesis of three-dimensional (3-D) hierarchical nanoporous carbon (HNC) supported transition metal phosphides (TMPs) for the first time by in situ growth of CoP nanoparticles (NPs) in CaCO3 NP-templated Cinnamomum platyphyllum leaf extract-derived carbon. They were subsequently employed as a HER catalyst, showing an onset potential of 7 mV and an overpotential of 95.8 mV to achieve 10 mA cm(-2), a Tafel plot of 33 mV dec(-1), and an exchange current density of 0.1182 mA cm(-2), of which the onset overpotential and the Tafel plot are the lowest reported for non-noble-metal HER catalysts, and the overpotential to achieve 10 mA cm(-2) and the exchange current density also compare favorably to most reported HER catalysts. In addition, this catalyst exhibits excellent durability with negligible loss in current density after 2000 CV cycles ranging from +0.01 to -0.17 V vs RHE at a scan rate of 100 mV s(-1) or 22 h of chronoamperometric measurement at an overpotential of 96 mV and a high Faraday efficiency of close to 100%. This work not only creates a novel high-performance non-noble-metal HER electrocatalyst and demonstrates the great advantages of the in situ grown 3-D HNC supported TMP NPs for the electrocatalysis of HER but also offers scientific insight into the mechanism for the in situ growth of TMP and their precursor NPs, in which an ultralow reactant concentration and rich functional groups on the 3-D HNC support play critical roles.

The effects of amine/nitro/hydroxyl groups on the benzene rings of redox additives on the electrochemical performance of carbon-based supercapacitors

In this work, a series of porous carbon materials with hierarchical porosities have been synthesized via a template carbonization method, in which cheap CaCO3 serves as a template and glucose as a carbon precursor. During the carbonization process, CO2 produced by the decomposition of the CaCO3 template can act as an internal activating agent, significantly improving microporosity and mesoporosity. All the carbon materials obtained by regulating the ratio of glucose to CaCO3 exhibit the amorphous features with a low graphitization degree. Among them, the carbon-1 : 2 sample shows a high BET surface area of up to 818.5 m(2) g(-1) and a large total pore volume of 1.78 cm(3) g(-1) as well as a specific capacitance of 107.0 F g(-1) at 1 A g(-1). In addition, a series of hydroquinone (HQ), p-aminophenol (PAP) and p-nitrophenol (PNP) as novel redox additives that can produce pseudo-capacitances have been added into the KOH electrolyte for promoting the total capacitive performances via redox reactions at the electrode-electrolyte interface. As expected, a 2.5-fold increase in the galvanostatic capacitance of 240.0 F g(-1) in the HQ-0.5 electrolyte occurs, compared with the conventional KOH electrolyte. Similarly, the PAP-0.5 electrolyte and the PNP-0.5 electrolyte also show a high specific capacitance of 184.0 F g(-1) at 2 A g(-1) (156.6 F g(-1) at 3 A g(-1)) and 153.0 F g(-1) at 3 A g(-1), respectively. Additionally, the three kinds of electrolytes exhibit excellent cyclic stability. The remarkable improvement of supercapacitors is attributed to the quick reversible Faradaic reactions of amine and hydroxyl groups adhering to the phenyl rings, which largely accelerates electron migration and brings additional pseudocapacitive contribution for carbon-based supercapacitors.

Morphology-dependent Electrochemical Enhancements of Porous Carbon as Sensitive Determination Platform for Ascorbic Acid, Dopamine and Uric Acid

Using starch as the carbon precursor and different-sized ZnO naoparticles as the hard template, a series of porous carbon materials for electrochemical sensing were prepared. Experiments of scanning electron microscopy, transmission electron microscopy and Nitrogen adsorption-desorption isotherms reveal that the particle size of ZnO has big impacts on the porous morphology and surface area of the resulting carbon materials. Through ultrasonic dispersion of porous carbon and subsequent solvent evaporation, different sensing interfaces were constructed on the surface of glassy carbon electrode (GCE). The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) were studied. On the surface of porous carbon materials, the accumulation efficiency and electron transfer ability of AA, DA and UA are improved, and consequently their oxidation signals enhance greatly. Moreover, the interface enhancement effects of porous carbon are also controlled by the particle size of hard template. The constructed porous carbon interface displays strong signal amplification ability and holds great promise in constructing a sensitive platform for the simultaneous determination of AA, DA and UA.

Hierarchical porous carbon materials prepared using nano-ZnO as a template and activation agent for ultrahigh power supercapacitors

Hierarchical porous carbon materials with a localized graphitic structure exhibit an outstanding high-rate performance.

Mesoporous carbon adsorbents from melamine-formaldehyde resin using nanocasting technique for CO2 adsorption

Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine-formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental (CHN) analysis, Fourier transform infrared (FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO2 capture. The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent-CO2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption-desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface.

Synthesis of nitrogen doped mesoporous carbons for carbon dioxide capture

Nitrogen doped mesoporous carbons were prepared from melamine-formaldehyde resin and mesoporous silica by nanocasting method followed by their characterization and CO₂ adsorption performance evaluation by fixed-bed experiments.

A hierarchical porous electrode using a micron-sized honeycomb-like carbon material for high capacity lithium-oxygen batteries

A micron-sized honeycomb-like carbon material (MHC) is prepared in a facile way using nano-CaCO3 as a hard template. A novel electrode for lithium-oxygen batteries is fabricated and displays a superior discharge capacity as high as 5862 mA h g(-1). The higher electrode space utilization is attributed to its hierarchical pore structure, with intrinsic mesopores in the MHC particles for Li2O2 depositions and macropores among them for oxygen transport.