To address aggravating environmental and energy problems, active, efficient, low-cost, and robust electrocatalysts (ECs) are actively pursued as substitutes for the current noble metal ECs. Therefore, in this study, we report the preparation of graphene flakes (GF) doped with S and N using 2-5-dimercapto-1,3,4-thiadiazole (S3N2) as precursor followed by the immobilization of cobalt spinel oxide (Co3O4) or manganese spinel oxide (Mn3O4) nanoparticles through a one-step co-precipitation procedure (Co/S3N2–GF and Mn/S3N2–GF). Characterization by different physicochemical techniques (Fourier Transform Infrared (FTIR), Raman spectroscopy, Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD)) of both composites shows the preservation of the metal oxide spinel structure and further confirms the successful preparation of the envisaged electrocatalysts. Co/S3N2–GF composite exhibits the best ORR performance with an onset potential of 0.91 V vs. RHE, a diffusion-limiting current density of −4.50 mA cm−2 and selectivity for the direct four-electron pathway, matching the results obtained for commercial Pt/C. Moreover, both Co/S3N2–GF and Mn/S3N2–GF showed excellent tolerance to methanol poisoning and good stability.
Biochar (BCH) is a carbon-based bio-material produced from thermochemical conversion of biomass. Several activation or functionalization methods are usually used to improve physicochemical and functional properties of BCHs. In the context of green and sustainable future development, activated and functionalized biochars with abundant surface functional groups and large surface area can act as effective catalysts or catalyst supports for chemical transformation of a range of bioproducts in biorefineries. Above the well-known BCH applications, their use as adsorbents to remove pollutants are the mostly discussed, although their potential as catalysts or catalyst supports for advanced (electro)catalytic processes has not been comprehensively explored. In this review, the production/activation/functionalization of metal-supported biochar (M-BCH) are scrutinized, giving special emphasis to the metal-functionalized biochar-based (electro)catalysts as promising catalysts for bioenergy and bioproducts production. Their performance in the fields of biorefinery processes, and energy storage and conversion as electrode materials for oxygen and hydrogen evolutions, oxygen reduction, and supercapacitors, are also reviewed and discussed.
Herein, S‐doped graphene flakes‐based composites with Fe3O4 and/or CuS nanoparticles (NPs) are reported as photo‐Fenton catalysts for the 4‐nitrophenol (4‐NP) degradation. The S‐doped graphene flakes (S‐GF) were prepared using a thermal treatment approach, and the nanocomposites by the in situ growth of Fe3O4 and/or CuS onto the S‐GF scaffold. The characterization methods confirmed the formation of two‐ and three‐components nanocomposites. The Fe3O4 NPs presented a cubic inverse spinel structure and the CuS phases a covellite structure, both with smaller crystallite sizes in the nanocomposites. The new nanocomposites showed higher ability to catalyze the photo‐Fenton 4‐NP degradation than the individual components. The S‐GF@CuS−Fe3O4 nanocomposite exhibited the best catalytic activity: 95.2 % of 4‐NP degradation, a kinetic of pseudo‐first order (k=0.016 min−1), high photo‐Fenton catalytic stability and catalyst's composition/structure preservation. The CuS NPs showed an important role in the photo‐Fenton‐like catalytic activity improvement.
A new application of graphene-type materials as an alternative cleanup sorbent in a quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure combined with GC–ECD/GC–MS/GC–MS/MS detection was successfully used for the simultaneous analysis of 12 brominated flame retardants in Capsicum cultivar samples. The chemical, structural, and morphological properties of the graphene-type materials were evaluated. The materials exhibited good adsorption capability of matrix interferents without compromising the extraction efficiency of target analytes when compared with other cleanups using commercial sorbents. Under optimal conditions, excellent recoveries were obtained, ranging from 90 to 108% with relative standard deviations of <14%. The developed method showed good linearity with a correlation coefficient above 0.9927, and the limits of quantification were in the range of 0.35–0.82 μg/kg. The developed QuEChERS procedure using reduced graphite oxide (rGO) combined with GC/MS was successfully applied in 20 samples, and the pentabromotoluene residues were quantified in two samples.
Recently, society has been experiencing an increase of the level of electromagnetic exposure, especially in the radiofrequency range. This issue is an outcome of all technologies that make use of such radiation to meet the human need for faster communication processes. For instance, 5G wireless technologies are now emerging throughout the world that will require electromagnetic waves of higher frequencies (up to 30 GHz) and more base stations (expected to be 60 times higher than the current number of 4G base stations) that will be placed closer to each other. [1] In addition, other technologies such as GPS, radar, and mobile phones are available that use radiofrequency electromagnetic radiation, thus actively contributing to all this undesired electromagnetic exposure. This excessive radiation may lead to malfunctions in the human health or affect the operation of surrounding electronic equipment. [2] Since it is not practical to diminish the electromagnetic (EM) radiation utilization because it is needed for all the abovementioned applications, the most straightforward strategy to reduce its impact is by recurring to electromagnetic interference (EMI) shielding.EMI shielding refers to the use of a screen/shield to attenuate or even eliminate the electromagnetic radiation in a desired space. The attenuation ability of a shield is quantified by the shielding effectiveness (SE), in dB. The EMI shielding is related
With the rise of electromagnetic radiation-based technologies, considerable attention has been drawn to developing and implementing innovative electromagnetic shielding materials. Carbon nanomaterials and conductive polymers have been appealing to both academia and industry as promising alternatives for the traditionally used metallic materials, owing to their lightness, flexibility, easy processability and resistance to corrosion, which are of special importance for textile applications. In this work, multiwalled carbon nanotubes (MWCNTs) and poly (3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) have been applied to cotton textile substrates by straightforward scalable dyeing and coating processes, respectively. These processes led to uniform and homogeneous coatings with distinct properties: the fabric coated with MWCNT presented higher thickness and lower loading of incorporated material than the textile coated with PEDOT:PSS (thickness: 995 μm vs. 208 μm; material loading: 9.4 wt.% vs. 70.7 wt.%). The electromagnetic shielding properties were outlined for each shielding textile in the frequency range of 5.85–18 GHz: an average shielding effectiveness of ~35.6 dB was obtained for MWCNT@tex, while PEDOT:PSS@tex reached ~38.3 dB. Thus, PEDOT:PSS provided enhanced radiation shielding with lower coating thickness, while the MWCNTs led to improved attenuation with less material usage. Shielding effectiveness values above 30 dB were obtained for both electromagnetic interference shielding textiles, which corresponds to an excellent classification for general use applications, such as casual clothing and maternity wear.
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