Graphene@Metal Sulfide/Oxide Nanocomposites as Novel Photo‐Fenton‐like Catalysts for 4‐Nitrophenol Degradation

Abstract

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.

Graphene-Type Materials for the Dispersive Solid-Phase Extraction Step in the QuEChERS Method for the Extraction of Brominated Flame Retardants from Capsicum Cultivars

“…Even though these two graphene-type materials were previously prepared and their characterization was reported in the literature, , here, a summary of the main aspects of their characterization is given for the sake of the reader to avoid labyrinthic access to data. The rGO was characterized by several techniques, namely, N 2 -adsorption isotherms, XRD, TEM, XPS, and Raman spectroscopy .…”

“…The graphene-type materials were prepared by procedures already reported. , Briefly, the rGO preparation consisted, in the first step, the addition of 10 g of graphite and over 200 mL of fuming HNO 3 , keeping the mixture at 0 °C. Then, 80 g of KClO 3 was gradually added over 2 h; afterward, the mixture was stirred for 21 h, maintaining the temperature of 0 °C.…”

“…The S-GF was prepared by milling 0.5 g of commercial graphene flakes (GF) together with 0.15 g of elemental sulfur in ball milling equipment (Retsch, MM200) for 5 h at a frequency of 15 s –1 using two zirconium oxide balls (1.5 cm in diameter). The obtained material was then pyrolyzed in a nitrogen atmosphere, heated up to 600 °C at a heating rate of 2 °C/min (Nabertherm), and maintained at this temperature for 1 h …”

Nanomaterials of Carbon and Metal Sulfides in Photocatalysis

“…As previously mentioned, Shi et al also stated that there is an optimal loading of CuS on rGO, showing that samples with 20% of rGO have better photocatalytic activity than samples containing 30% of rGO [120]. This has been explained by the effect on the stacking of graphene sheets and metal-sulfide particle aggregation, which results from the presence of a high amount of carbon nanomaterials (rGO or graphene) employed in the composite structure [155,158]. Wang et al have found that the synergistic interaction occurring between graphene and metal-sulfide phases in CuS/graphene, with an impact on the electronic conductivity of graphene and CuS/graphene morphology, accounts for the observed stability and photoactivity of such heterostructures [159].…”

“…Wang et al have found that the synergistic interaction occurring between graphene and metal-sulfide phases in CuS/graphene, with an impact on the electronic conductivity of graphene and CuS/graphene morphology, accounts for the observed stability and photoactivity of such heterostructures [159]. Matos et al have synthesized hybrid composites comprising S-doped graphene decorated with CuS and Fe 3 O 4 semiconductor phases, which showed higher photocatalytic ability than their individual components in the photodegradation of 4-nitrophenol, in addition, these photocatalysts could be recovered and reused in subsequent cycles [158].…”