In the present study, mpg-C3N4/Ag/ZnO NWs/Zn photocatalyst plates were fabricated through facile dip-coating process of silver (Ag) and mesoporous graphitic carbon nitride (mpg-C3N4) onto zinc oxide nanowires (ZnO NWs) previously formed by electrochemical anodizing of Zn plates. The structure, optical and electrochemical characterizations of the fabricated samples were investigated by XRD, FESEM, EDX, TEM, FTIR, BET, PL, UV–vis DRS, and EIS analyses. To evaluate the photocatalytic activity of the plates, the main key factors such as number of photocatalyst plates, dye concentration, initial pH, and reaction time for the degradation of Direct Orange 26 (DO26) dye under ultraviolet (UV) light illumination were studied. The best photocatalytic efficiency of 94 % was achieved using four photocatalyst plates, 10 mg/L DO26, and pH = 6 in 120 min of reaction time. The integration of the mpg-C3N4/Ag/ZnO NWs/Zn plates, adsorption, and photolysis inferred the existence of a synergy index of 5 for the degradation of target pollutant. In the presence of edetate disodium (EDTA-2Na) and ethanol (EtOH), degradation efficiency of DO26 was remarkably dropped to 43.6 % and 19.3 % by the photocatalytic process respectively, indicating the major role of h+ and OH in the destruction of target molecules. The overwhelming photocatalytic mechanism of the photocatalyst was further clarified for the elimination of DO26. The fabricated photocatalyst demonstrated remarkable stability and recyclability for four consecutive catalytic cycles. Fabrication of the mpg-C3N4/Ag/ZnO NWs/Zn plates is anticipated to be a rational design for photocatalytic degradation of various pollutants.

Facile fabrication of mpg-C3N4/Ag/ZnO nanowires/Zn photocatalyst plates for photodegradation of dye pollutant

The superior photocatalytic activity of Nb doped TiO2/g-C3N4 direct Z-scheme system for efficient conversion of CO2 into valuable fuels.

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Reduced Graphene Oxide/Mesoporous ZnO NSs Hybrid Fibers for Flexible, Stretchable, Twisted, and Wearable NO2 E-Textile Gas Sensor.

Currently, fabricating a narrow bandgap photocatalyst that can degrade pollutants in natural sunlight is critical but inspiring. In this study, a hybrid g-C3N4/Cr-ZnO nanocomposite was synthesized by a simple chemical co-precipitation method and its photocatalytic and antimicrobial properties were explored. In the first step, the photocatalytic efficiency of Cr-ZnO (1−9 wt. %) nanoparticles were carried out to find out the optimum doping of Cr into ZnO. The as-prepared 5% Cr-ZnO nanoparticles demonstrated the best optical absorption of sunlight and methylene blue degradation and in the second step; these were dispersed on g-C3N4 nanosheets as an active component to form ternary heterostructured photocatalyst. The nanoparticles and composite photocatalysts were characterized by X-ray diffraction spectroscopy, energy-disperse X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy. The optimized composite (60 %g-C3N4/5%Cr-ZnO) performed enhanced harvesting of solar energy compared to ZnO, g-C3N4 and g-C3N4/ZnO composite, achieving 93 % methylene blue dye degradation in 90 min. The improved photocatalytic activity of composite can be attributed to the better absorption and electron-hole pair separation between g-C3N4 and Cr-ZnO. The photocatalytic stability of the composite was testified by cyclic tests. The antibacterial aptitude of the samples was investigated against Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis, Staphylococcus aureus and Streptococcus salivarius) bacteria applying diffusion well method. The 60 %g-C3N4/5%Cr-ZnO nanocomposite exhibits higher antibacterial activity compared to other samples. The enriched photocatalytic and antimicrobial activities of the composite may be predominantly ascribed to the synergistic effect of the heterojunction developed between g-C3N4 and Cr-ZnO.

Highly efficient g-C3N4/Cr-ZnO nanocomposites with superior photocatalytic and antibacterial activity

Morphology engineering of photoelectrodes for efficient photoelectrochemical water splitting

Metal (M)-doped ZnO/g-C3N4 composites with a sponge-like porous structure have been synthesized by a facile one-pot pyrolysis method. A representative composite, magnesium (Mg)-doped ZnO/g-C3N4 composite was analyzed to contain a 13.7 at% of ZnO and Mg at a standard condition. ZnO and Mg were uniformly distributed over the composite without the formation of clearly separated phases. Optical properties of the composite revealed the extension of light absorption range and the suppressed carrier recombination. Most notably, the photocatalytic efficiency of the Mg-doped ZnO/g-C3N4 composite overwhelmed those of pure ZnO, pure g-C3N4, ZnO/g-C3N4 composite, and ZnO/g-C3N4 composites doped with other metals. Its photoreaction rate constant was estimated to be even higher than the previous reports. A physical mechanism was proposed to account for the observed enhancement of the photocatalytic activity. The synthetic approach and the demonstrated performance of this work may present new direction towards high-performance photocatalysts using composites of g-C3N4 and ZnO.

Facile synthesis of porous metal-doped ZnO/g-C3N4 composites for highly efficient photocatalysts

A crystal-damage-free nanodoping method, which utilized the vacuum drive-in diffusion of Al into ZnO nanorods, was developed. In this method, vertical ZnO nanorod arrays that were grown by chemical bath deposition beforehand were deposited with Al thin film and subsequently heat-treated under a high vacuum. At an optimum condition, the surface Al atoms were completely diffused into ZnO nanorods, resulting in Al-doped ZnO nanorods. Stretchable gas sensors were fabricated by sequentially drop-casting the Al-doped ZnO nanorods and silver nanowires on polydimethylsiloxane substrate. The resistance and response of the sensor could be optimized through the elaborate control of relative densities of Al-doped ZnO nanorods and silver nanowires. The sensor showed a high response of 32.3% to 10 ppm of NO2 gas at room temperature, even under a large strain of 30%. The NO2-sensing mechanism of Al-doped ZnO nanorod/silver nanowire bilayer sensors is discussed on the basis of a synergistic interplay of Al-doped ZnO nanorods and silver nanowires.

Diffusion-Driven Al-Doping of ZnO Nanorods and Stretchable Gas Sensors Made of Doped ZnO Nanorods/Ag Nanowires Bilayers.

In this work, graphitic carbon nitride (g-C3N4) was synthesized by simple pyrolysis of melamine, and it was hybridized with reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) using a stepwise solution method. AgNPs were randomly distributed on the surface of rGO/g-C3N4 layered hybrid structure, forming Ag@rGO/g-C3N4 composite. It was disclosed that the Ag@rGO/g-C3N4 composite responded to both oxidizing and reducing gases at room temperature, and its response was greatly enhanced from those of pristine rGO and rGO/g-C3N4. The room temperature responses of the composite were estimated at − 95% and 8% for 50 ppm of NO2 and NH3, respectively. The roles of structural components were discussed, and a gas-sensing mechanism was proposed based on the respective roles. In particular, AgNPs turned out to play an important role in the gas-sensing activity.

Gitae Namgung

Papers

Facile synthesis of porous metal-doped ZnO/g-C3N4 composites for highly efficient photocatalysts

Diffusion-Driven Al-Doping of ZnO Nanorods and Stretchable Gas Sensors Made of Doped ZnO Nanorods/Ag Nanowires Bilayers.

Synthesis of Ag@rGO/g-C 3 N 4 Layered Structures and Their Application to Toxic Gas Sensors: Effect of Ag Nanoparticles

Plasmonic Ag nanowires sensitized ZnO flake-like structures as a potential photoanode material for enhanced visible light water splitting activity

Facile growth of novel morphology correlated Ag/Co-doped ZnO nanowire/flake-like composites for superior photoelectrochemical water splitting activity