Abstract
N-doped graphene-ZnO hybrid materials with different N-doped graphene:ZnO wt% ratios (1:10; 1:20; 1:30) were prepared by a simple and inexpensive sol-gel method. The materials denoted NGr-ZnO-1 (1:10), NGr-ZnO-2 (1:20), and NGr-ZnO-3 (1:30) were investigated with advanced techniques and their morpho-structural, photocatalytic, and electrocatalytic properties were reported. Hence, pure N-doped graphene sample contains flakes with the size ranging from hundreds of nanometers to micrometers. In the case of all NGr-ZnO hybrid materials, the flakes appear heavily decorated with ZnO nanoparticles, having a cauliflower-like morphology. The X-ray powder diffraction (XRD) investigation of N-doped graphene sample revealed that it was formed by a mixture of graphene oxide, few-and multi-layer graphene. After the ZnO nanoparticles were attached to graphene, major diffraction peaks corresponding to crystalline planes of ZnO were seen. The qualitative and quantitative compositions of the samples were further evidenced by X-ray photoelectron spectroscopy (XPS). In addition, UV photoelectron spectroscopy (UPS) spectra allowed the determination of the ionization energy and valence band maxima. The energy band alignment of the hybrid materials was established by combining UV–Vis with UPS results. A high photocatalytic activity of NGr-ZnO samples against rhodamine B solution was observed. The associated reactive oxygen species (ROS) generation was monitored by electron paramagnetic resonance (EPR)-spin trapping technique. In accordance with bands alignment and identification of radical species, the photocatalytic mechanism was elucidated.
Highlights
In recent years, constant efforts have been made to acquire facile and cost-effective methods to resolve environmental problems using eco-friendly and functional materials
As can be seen in this figure, carbon is uniformly distributed within the material, while zinc and oxygen are found in ZnO nanoparticles, proving their attachment to N-Doped Graphene (NGr) surface
We report a simple route to synthesize N-doped graphene-ZnO hybrid materials through the electrochemical exfoliation of graphite rods followed by a sol-gel process
Summary
Constant efforts have been made to acquire facile and cost-effective methods to resolve environmental problems using eco-friendly and functional materials. ZnO has found application in removing various contaminants due to its nontoxic nature, low cost correlated with high photosensitivity, chemical and physical stability [1,2,3]. ZnO has several deficiencies like the limit of UV-light adsorption due to the wide band gap, fast recombination of photo generated electron-hole pairs [4], and relatively poor electrical conductivity [5]. Possessing high mobility, good conductivity, great mechanical flexibility and excellent chemical stability, graphene is a suitable modifier for improving ZnO catalytic performances. Several papers reported the use of graphene oxide (GO) [8] and its reduced form (rGO) [9] as a photocatalytic performance enhancer for ZnO [10,11]. The electrochemical exfoliation of graphite is a promising way to produce high-quality graphene in an easier way and with lower costs [14,15]
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