Built-in electric field activates endogenous redox couple for self-sustained Fenton-like reaction.

Non-platinum nanocatalyst on porous nitrogen-doped carbon fabricated by cathodic vacuum arc plasma technique

Porous, thick nitrogen-doped carbon encapsulated large PtNi core-shell nanoparticles for oxygen reduction reaction with extreme stability and activity

Nitrogen-doped porous carbons are attracting considerable attention as adsorbents in CO2 uptake area or for supercapacitors. In this work, nitrogen-doped porous carbons with a high surface area are efficiently prepared through a facile approach by using polyvinylpyrrolidone as carbon and nitrogen sources through ZnCl2 activation at 400–700 °C for 4 h under N2 atmosphere. The obtained nitrogen-doped porous carbons exhibit a narrow microporous structure (0.4–1.0 nm), high specific surface area (up to 1040 m2 g−1) and corresponding N content of up to 6.3 wt%. These findings are ascribed to the unique features of high specific surface area and rich N content. Such nitrogen-doped porous carbons show high CO2 capture of 4.0 mmol g−1 (0 °C) and 2.5 mmol g−1 (25 °C), as well as excellent capacitive performance with a specific capacitance of 292 F g−1 (in 2 M KOH) at a current density of 0.5 A g−1 and cycling stability. A symmetrical supercapacitor based on NPCs shows high energy density (23.2 W h kg−1 at 0.5 A g−1) and good cycle stability (96.8% capacitance retention after 5000 cycles) in symmetric two-electrode systems.

Electrochemical performance of polyacrylamide hydrogel based nitrogen-doped porous carbon for supercapacitor

One-dimensional covalent organic framework as a robust carrier for enhanced lipase immobilization and catalytic performance

Nitrogen-doped porous carbons were prepared using a facile method, with low-biotechnology fulvic acid potassium salts as a precursor. The prepared carbons had a high surface area (1623 m2 g−1) and good electrochemical properties, making them suitable electrode materials for supercapacitors. Nitrogen-doped porous carbons were tested as an electrode in both 6 M KOH aqueous solution and different concentrations KNO3 aqueous solution. The nitrogen-doped porous carbons with unique microstructure and nitrogen functionalities exhibited a capacitance of 235 F g−1 in a 6 M KOH aqueous solution. Electrochemical investigation showed that the nitrogen-doped porous carbons exhibited a broad potential operational window in a 2.5 M KNO3 aqueous solution. Furthermore, a high capacitance retention of 88.1 % was achieved even after 5000 cycles at 1.7 V. Potassium nitrate solutions in a wide range of concentrations were also proven to be promising electrolytes for electrochemical capacitors because they are cheap, noncorrosive, electrochemically stable, and compatible to diverse current collectors.

Introduction Nitrogen-doped carbon materials have been attracting great attention as one of the promising metal-free oxygen reduction reaction (ORR) catalysts due to the abundant resources, chemical stability, and high electronic conductivity, which could replace the high cost platinum-based materials limiting expansion of application fields of the fuel cells. Generally, nitrogen-doped carbons have been prepared by chemical vapor deposition with precursors containing nitrogen (pyridine or acetonitrile, etc.)[i], or by thermal/plasma treatment using graphitic carbons.[ii] The active site of nitrogen-doped carbons is yet controversial, though it has been suggested that incorporation of nitrogen atoms in the sp2 carbon network structures enhances ORR activity through active site formation by produced pyridinic N or graphitic N.1 Together with the nitrogen doped structures, the amount of the doped nitrogen atoms, surface area and degrees of graphitization can affect the ORR performance[iii] and control techniques of these factors are crucial to achieve the higher catalytic activity. Herein we fabricated the nitrogen-doped carbon from covalent organic frameworks (COFs) which have molecularly-ordered structures constructed by covalent linkage of organic building blocks. Due to the above unique structures and properties, COFs are promising for potential applications in gas storage, optoelectronic devices and catalysis.[iv] In this study, we focus on the structural features of COFs, which are versatile molecular design based on various combination of the building block molecules and the covalent bonding and highly porous structures. Thus we have been examining carbonization of COFs having hetero atoms such as N and B to create hetero atom doped carbon materials from the molecularly-ordered starting materials, COFs. Herein we synthesized two types of the nitrogen atom-containing COFs as the precursors. After carbonization, we found that the nitrogen-doped porous carbons were fabricated with high surface areas. The obtained materials would be useful to examine the effect of structural differences of the resulting nitrogen-doped structures on ORR activity to develop highly active carbon catalysts. Experiment Synthesis of COF1[v]Benzene-1,3,5-tricarboxylate (1, 24 mg) and phenylendiamine (2, 24 mg) were dissolved in dioxane (2.5 ml), respectively. After mixing the solutions, 3.0 M aqueous acetic acid (0.25 ml) was added. Two-day storage at 25 °C was found to generate a precipitate, which was collected by filtration, then washed with acetone. The obtained solid was dried overnight in vacuo at 80 °C to provide a yellow powder (COF1). Synthesis of ACOF-1 1 (24 mg) and hydrazine (3, 19 ml) were dissolved in dioxane (1.0 ml). Then 6.0 M tetrafluoroacetic acid (0.13 ml) was added. The solution was heated at 120 °C in a pressure resistant vessel yielding a precipitate, which was collected by filtration, then washed with acetone. The obtained solid was dried overnight in vacuo at 80 °C to provide a pale yellow powder (ACOF-1). Carbonization of COFs The obtained COF1 and ACOF-1 were heated at 800 °C for 3 h under N2 flow. Result and Discussion The XRD patterns of the obtained COFs show obvious diffraction peaks, which indicate crystalline structure formation. For porous structure investigation, N2 gas adsorption measurements were conducted. Based on the BET analysis, the surface area of COF1 and ACOF-1 were estimated to be 1528 m2/g and 1484 m2/g respectively. These results reveal that the prepared COFs have highly ordered structures with large surface areas. After carbonization of the both COFs, in Raman spectra, two peaks were observed at around 1300 cm-1 and 1590 cm-1, which are attributed to D band and G band of graphitic carbon structures. From deconvoluted XPS spectra of the N1s, three peaks were observed at 398, 400, and 402 eV ascribable to pyridinic, pyrrolic, and graphitic N. The results exhibit that the carbonized COFs have nitrogen-doped graphitic structures. The BET surface area of the carbonized COF1 and the carbonized ACOF-1 were calculated to be 538 m2/g and 1257 m2/g, respectively. Interestingly, the carbonized ACOF-1 showed a similar surface area to one before carbonization. This result indicates that COFs would be capable of producing porous carbon structures. The electrocatalytic properties of the carbonized ACOF-1 for ORR were investigated by cyclic voltammetry (CV) in 0.1M KOH saturated with N2 or O2 gas. Though no peak was observed in a N2 atmosphere condition, a significant reduction peak appeared at -0.198 V under an O2 atmosphere, which indicates ORR catalytic activity from the material. [i] M. Kawaguchi et al. Chem. Mater. 1996, 8, 1197. [ii] X. Wang et al. Science, 2009, 324, 768. [iii] C. H. Choi et al. ACS nano, 2 012, 6, 7084. [iv] A. P. Cote et al. Science, 2005, 310, 1166. [v] T. Shiraki et al. Chem. Lett. 2015, 44, 1488. Figure 1

Fabrication of Bi4O5Br2-decorated rod-like MOF-derived MoS2 hierarchical heterostructures for boosting photocatalytic CO2 reduction

ZIF-8-derived nitrogen-doped porous carbon supported CuFeO2 for sulfamethoxazole removal: Performances, degradation pathways and mechanisms

The present study investigated the involvement of key molecular regulators of oxidative stress in amoebic gill disease (AGD), a parasitic infestation in Atlantic salmon. In addition, the study evaluated how these molecular biomarkers responded when AGD-affected fish were exposed to a candidate chemotherapeutic peracetic acid (PAA). Atlantic salmon were experimentally infected with the parasite Neoparameoba perurans, the causative agent of AGD, by bath exposure and after 2 weeks, the fish were treated with three commercial PAA products (i.e., Perfectoxid, AquaDes and ADDIAqua) at a dose of 5 ppm. Two exposure durations were evaluated – 30 min and 60 min. Sampling was performed 24 h and 2 weeks after PAA treatment (equivalent to 2- and 4-weeks post infection). At each sampling point, the following parameters were evaluated: gross gill pathology, gill parasitic load, plasma reactive oxygen species (ROS) and total antioxidant capacity (TAC), histopathology and gene expression profiling of genes with key involvement in oxidative stress in the gills and olfactory organ. AGD did not result in systemic oxidative stress as ROS and TAC levels remained unchanged. There were no clear patterns of AGD-mediated regulation of the oxidative stress biomarkers in both the gills and olfactory organ; significant changes in the expression were mostly related to time rather than infection status. However, the expression profiles of the oxidative stress biomarkers in AGD-affected salmon, following treatment with PAA, revealed that gills and olfactory organ responded differently – upregulation was prominent in the gills while downregulation was more frequent in the olfactory organ. The expression of catalase, glutathione S-transferase and thioredoxin reductase 2 was significantly affected by the treatments, both in the gills and olfactory organ, and these alterations were influenced by the duration of exposure and PAA product type. Parasitic load in the gills did significantly increase after treatment regardless of the product and exposure duration; the parasite was undetectable in some fish treated with AquaDes for 30 mins. However, PAA treated groups for 30 min showed lower macroscopic gill scores than the infected-untreated fish. Histology disclosed the classic pathological findings such as multifocal hyperplasia and increased number of mucous cells in AGD-affected fish. Microscopic scoring of gill injuries showed that AGD-infected-PAA-treated fish had lower scores, however, an overall trend could not be established. The morphology and structural integrity of the olfactory organ were not significantly altered by parasitism or PAA treatment. Collectively, the results indicate that AGD did not affect the systemic and mucosal oxidative status of Atlantic salmon. However, such a striking profile was changed when AGD-affected fish were exposed to oxidative chemotherapeutics. Moreover, the gills and olfactory organ demonstrated distinct patterns of gene expression of oxidative stress biomarkers in AGD-infected-PAA-treated fish. Lastly, PAA treatment did not fully resolve the infection, but appeared not to worsen the mucosal health either.

Utilizing spatial confinement effect of N atoms in micropores of coal-based metal-free material for efficiently electrochemical reduction of carbon dioxide

Energy shortage and wasting of resources are two main challenges for human society. To solve these problems, nitrogen-doped porous carbon was synthesized through a simple thermally induced phase separation (TIPS) method with subsequent carbonization and activation with biomass konjac/polyacrylonitrile composites as the raw materials and nitrogen source for the first time. The obtained composite carbon with hierarchical porosity, large specific surface areas, and high content of nitrogen doping shows promise due to its desirable electrochemical performance. Nitrogen-doped porous carbon exhibits a high specific capacitance of 390 F g-1 in a three-electrode system and a good rate characteristic with 70% capacitance retention at 20 A g-1. Excellent stabilization was observed with only a 4.5% capacitance decay under 10 000 cycles at 5 A g-1. The practical application of the composite porous carbon on flexible symmetrical supercapacitors was evaluated, showing a maximum energy density of 9.0 W h kg-1 when the power density was 250.2 W kg-1. More importantly, the fabricated flexible supercapacitor could still keep an excellent supercapacitor performance under bending and shows only a slight capacitance loss of 9% even after 1000 cycles (180°) of repetitive bending. The current study promotes the development of nitrogen-doped carbon materials on flexible energy storage devices.

Optimized sulfur-loading in nitrogen-doped porous carbon for high-capacity cathode of lithium–sulfur batteries

Porous carbon with a high surface area and controllable pore size is needed for energy storage. It is still a significant challenge to produce porous carbon in an economical way. Nitrogen-doped porous carbon (N-PC) was prepared through carbonization of a mixture of waste PET-derived metal–organic frameworks (MOFs) and ammonium. The obtained N-PC exhibits a large surface area and controlled pore size. When utilized as an electrode material for supercapacitors, the N-PC exhibits a specific capacitance of 224 F g−1, significantly surpassing that of commercial activated carbon (AC), which has a capacitance of 111 F g−1. In the subsequent capacitive deionization (CDI) tests, the N-PC demonstrated a maximum salt adsorption capacity of 19.9 mg g−1 at 1.2 V in a NaCl electrolyte (0.5 g L−1), and the salt adsorption capacity increased to 24.7 mg g−1 at 1.4 V. The N-PC electrode also exhibited superior regeneration. The present work not only presents a potential approach to develop cost-effective electrodes for seawater purification but also paves the way for recycling of waste plastics into high value-added products.

Fabricating high-loading Fe-N4 single-atom catalysts for oxygen reduction reaction by carbon-assisted pyrolysis of metal complexes