Graphitic carbon nitride (g-C3N4)-assisted materials for the detection and remediation of hazardous gases and VOCs

Synthesis of novel nanocomposite of g-C3N4 coated ZnO-MoS2 for energy storage and photocatalytic applications

Fabrication of heterostructures for energy storage and environmental remedial applications is an interesting subject of research that has been undertaken in this present investigation. The incorporation of g-C3N4 into ZnO:MoS2 heterojunction nanocomposite was accomplished by wet-chemical route and characterized by various techniques to ascertain its structure, morphology, and study its potential electro-optical characteristics. The g-C3N4@ZnO:MoS2 sample was investigated by x-ray diffraction (XRD) which reveals the co-existence of the ZnO, MoS2 and C3N4 phases linked to characteristic crystallographic planes in the spectrum, validating the formation of ternary nanocomposite. The XRD patterns of the pristine samples were also considered as reference to understand the structural evolution and phase transformations. Field emission scanning electron microscopy (FESEM) study states the formation of heterogeneous nanostructures having nanoparticles embedded on 2-D nanosheets like structures. Studies using energy dispersive spectroscopy (EDS) and elemental mapping show that all the elements that are linked to the above hybrid nanocomposite are present. Transmission electron microscopy (TEM) provided clear insights on the microstructure as we can identify the distribution of ZnO and MoS2 nanostructures on layered g-C3N4 nanosheets. The chemical composition and oxidation states of elements were elucidated by X-ray photoelectron spectroscopy (XPS) study, which added another layer of confirmation on the structural evolution of the ternary nanocomposite. Fourier transformed infrared (FTIR) study revealed the layered structure of sp2 hybridized bonding features of C and N in g-C3N4, besides Zn-O and Mo-S stretching vibrations. The nanocomposite demonstrated improved photodegradation efficacy and decomposed alizarin red and methylene blue dyes significantly with better stability and reusability. MoS2 as a co-catalyst acts as an electron acceptor/accelerator in the Z-scheme composite photocatalysis leading to improved photocatalytic efficiency. The resulting heterostructured material delivered a higher specific capacitance of 10.85 F/g with good capacitance retention. Electrochemical study revealed the energy storage capability of the hybrid system.

First-principles insights into the C6N7 monolayer as a highly efficient sensor and scavenger for the detection of selective volatile organic compounds

The design of new gas sensors and scavengers of volatile organic compounds (VOCs) is desirable for VOC enriching, separation and utilization. Herein, first-principles methods were performed to investigate the potential of C6N7 monolayers as highly efficient sensors and scavengers for selective VOCs (toluene, benzene, vinyl chloride, ethane, methanal, acetone, ethanol, and acetaldehyde). The physisorption of toluene, benzene, acetone, ethanol, acetaldehyde, and methanal has relatively high adsorption strength and can significantly tune the electronic properties and work function (Φ) of the C6N7, indicating that the C6N7 monolayer is highly sensitive and selective to these VOC gases. In addition, the desorption time of benzene, acetone, ethanol, acetaldehyde, and methanal is about 3, 0.4, 2.0 × 10-2, 3.0 × 10-2, and 3.6 × 10-5 s at 300 K, respectively, indicating that the C6N7-based sensor has high reusability at room temperature. The recovery time of toluene was about 7.8 × 102 s at 300 K, showing disposable toluene gas sensing of the monolayer. Our work confirms that the C6N7 monolayer as a resistance-type and Φ-type gas sensor and scavenger is highly sensitive, selective and reusable for VOCs (benzene, acetone, ethanol, acetaldehyde, and methanol), but is a disposable toluene gas sensor and scavenger at room temperature.