The adsorption and sensing behavior of three typical industrial toxic gases NO, NO2 and SO2 by the Pd modified C3N monolayer were studied in this work on the basic first principles theory. Meanwhile, the feasibility of using the Pd doped C3N monolayer (Pd-C3N) as a sensor and adsorbent for industrial toxic gases was discussed. First, the binding energies of two doping systems were compared when Pd was doped in the N-vacancy and C-vacancy sites of C3N to choose the more stable doping structure. The result shows that the doping system is more stable when Pd is doped in the N-vacancy site. Then, on the basis of the more stable doping model, the adsorption process of NO, NO2 and SO2 by the Pd-C3N monolayer was simulated. Observing the three gases adsorption systems, it can be found that the gas molecules are all deformed, the adsorption energy (Ead) and charge transfer (QT) of three adsorption systems are relatively large, especially in the NO2 adsorption system. This result suggests that the adsorption of the three gases on Pd-C3N belongs to chemisorption. The above conclusions can be further confirmed by subsequent deformable charge density (DCD) and density of state (DOS) analysis. Besides, through analyzing the band structure, the change in electrical conductivity of Pd-C3N after gas adsorption was studied, and the sensing mechanism of the resistive Pd-C3N toxic gas sensor was obtained. The favorable adsorption properties and sensing mechanism indicate that the toxic gas sensor and adsorbent prepared by Pd-C3N have great application potential. Our work may provide some guidance for the application of a new resistive sensor and gas adsorbent Pd-C3N in the field of toxic gas monitoring and adsorption.

https://www.mdpi.com/2079-4991/11/5/1267/pdf

First-Principles Insight into Pd-Doped C3N Monolayer as a Promising Scavenger for NO, NO2 and SO2.

To gain valuable insights into the applicability of Pd-decorated carbon nitride (C3N) monolayer as chemical gas sensor for the detection of CH4 and CO2 molecules, we have explored the adsorption properties of Pd-C3N nanosheets for detection of methane (CH4) and carbon dioxide (CO2) molecules. Firstly, the stability of Pd binding to the C3N monolayer was probed based on the adsorption energy analysis. We found that the binding of Pd to the top of N site is the most preferred position for adsorption process. The results of CH4 and CO2 adsorption showed that Pd-decorated C3N nanosheet possesses strong adsorption performance towards these gases, leading to the stable adsorption on the Pd site of Pd-C3N monolayer through forming strong chemical bonds. Moreover, the band structure analyses indicated the semiconducting behavior for CH4 and CO2 adsorbed Pd-C3N monolayers. Our DFT computations would be important to expound the strong sensing application of Pd-decorated C3N systems as a novel nanomaterial for gas detection.

Adsorption of CO2 and CH4 molecules on the Pd-decorated C3N based sensors: A first-principles study

It is of great significance to develop ethanol sensors with high sensitivity and low detection temperature. Hence, we prepared Au-supported material on mesoporous ZnO composites derived from a metal-organic framework ZIF-8 for the detection of ethanol gas. The obtained Au/ZnO materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (SEM), field emission transmission electron microscopy (TEM) and nitrogen adsorption and desorption isotherms. The results showed that the Au/ZnO-1.0 sample maintains a three-dimensional (3D) dodecahedron structure with a larger specific surface area (22.79 m2 g−1) and has more oxygen vacancies. Because of the unique ZIF structure, abundant surface defects and the formation of Au-ZnO Schottky junctions, an Au/ZnO-1.0 sensor has a response factor of 37.74 for 100 ppm ethanol at 250 °C, which is about 6 times that of pure ZnO material. In addition, the Au/ZnO-1.0 sensor has good selectivity for ethanol. According to density functional theory (DFT) calculations, the adsorption energy of Au/ZnO for ethanol (−1.813 eV) is significantly greater than that of pure ZnO (−0.217 eV). Furthermore, the adsorption energy for ethanol is greater than that of other gases.

https://www.mdpi.com/1424-8220/21/13/4352/pdf

Ethanol Sensing Properties and First Principles Study of Au Supported on Mesoporous ZnO Derived from Metal Organic Framework ZIF-8.

Two-dimension black arsenic-phosphorus as a promising NO sensor: A DFT study

The effects of small organic molecule (SOM) adsorption with benzene (C6H6), hexafluorobenzene (C6F6), and p-difluorobenzene (C6H4F2) on the electronic properties of stanene under external electric fields are investigated through first-principles calculations. Different adsorption sites and molecular orientations are considered to determine the most stable configurations of small organic molecule (SOM) adsorption on the surface of stanene. The results show that the internal electric field caused by the adsorption of small organic molecules destroys the symmetry of the two sublattices of stanene in C6H6/stanene, C6F6/stanene and C6H4F2/stanene systems with the most stable configurations, opening the band gaps of stanene with 39.5, 18.9 and 14.5 meV, respectively. Under an external electric field, a wide range of linearly tunable and sizable direct band gaps (31.6–420.1 meV for the C6H6/stanene system, 14.8–587.2 meV for the C6F6/stanene system and 14.5–490.2 meV for the C6H4F2/stanene system) are merely determined by the strength of the composite electric field despite its direction. The mechanism of charge transfer between stanene and organic molecules under an external electric field can be revealed using an equivalent capacitor model to explain the tunable charge transfer. More importantly, the high carrier mobility of the stable SOM/stanene systems under an external electric field is largely retained due to the weak interactions at the interface. These results indicate that the electronic properties of stanene can be effectively modulated by the surface adsorption of organic molecules under an external electric field, providing effective and reversible routes to enhance the performance of stanene for novel electronic devices in the future.

Shupeng Liu

Papers

Adsorption of nitrogen based gas molecules on noble metal functionalized carbon nitride nanosheets: A theoretical investigation