Adsorption of Gas Molecules on Graphene‐Like ZnO Nanosheets: The Roles of Gas Concentration, Layer Number, and Heterolayer

Abstract

ZnO also has a multitude of 1D nanomorphologies, [3,4] for example, nanowires, [5] nanotubes, [6] nanorods, [7] nanoribbons, [8] etc. This versatile functional material has attracted significant research attention because of its excellent properties such as sizable direct band gap of ≈3.3 eV and large exciton binding energy of 60 meV and so on, which make it an excellent candidate for a variety of applications like piezoelectric devices, [9] light emitting diodes, [10] biosensors, [11] catalysis, [12] etc. Apart from those applications, ZnO has also been extensively investigated as gas sensors, in particular, the 1D ZnO nanostructures exhibit much higher sensitivity than the polycrystalline bulk ones owing to the high surface-to-volume ratio. [13][14][15][16][17] Recently, another type of nanostructure of ZnO, namely, the atomic-thinned g-ZnO monolayer, was theoretically predicted [18,19] and experimentally realized. [20][21][22] It has the honeycomb structure very similar to that of single-layered hexagonal boron nitride (h-BN), with the band gap predicted to be 3.57-5.64 eV, larger than the one of the bulk wurtzite ZnO. [23] As the mutual merit shared by the 2D materials, [24][25][26][27][28][29][30] monolayer g-ZnO has even larger surface area than its 1D counterparts with the same volume. Inspired by the previous researches of unique gas adsorption performance of various 2D materials, [26,[31][32][33][34][35][36][37][38][39][40][41][42][43] it is of scientific interests to investigate the gas adsorption performance of g-ZnO and explore its suitability to be gas sensing materials. However, relevant systematical investigations of gas adsorption performance of pristine g-ZnO are relatively scarce. [44,45] In this paper, we employ first principle calculations based on the density functional theory (DFT) to gain fundamental insights into the interaction between gas molecules and pristine g-ZnO. This study mainly focuses on the following questions: (i) What is the adsorption behavior of the common atmospheric (CO 2 , H 2 O, and O 2 ) and toxic (CO, H 2 S, NH 3 , SO 2 , NO, and NO 2 ) gas molecules on g-ZnO? (ii) Will the adsorption strength be affected by the gas concentration? (iii) What is the impact of the layer numbers of g-ZnO on the adsorption? (iv) Do the heterolayers or substrates have effects on the adsorption? To solve the issues above, we utilized different supercell sizes of g-ZnO to simulate the gas concentration effect, that is, a large supercell gives rise to lower gas density. Besides, we also 2D layered materials have gained tremendous research interests for gas sensing applications because of their ultrahigh theoretical specific surface areas and unique electronic properties, which are prone to be influenced by external factors. Here, using first principle calculations, the adsorption of several common gas molecules on graphene-like ZnO (g-ZnO) is systematically studied by taking the gas concentration, homolayer number, and heterolayers into considerations. The calculation results show that the a...

1T′-MoS2, A Promising Candidate for Sensing NOx

“…Also, Chen et al found that the adsorption strengths of NH 3 and NO 2 on g-ZnO increase with the number of layers. They attributed the enhancement of adsorption strength to vdW forces between molecules and sublayers . In their case, the adsorption enhancement of NH 3 with the layer number is probably because of the N-metal (including sublayer Zn) interactions, while in MoS 2 , the weaker H­(NH 3 )–S­(MoS 2 ) interactions are less likely to be enhanced by sublayers compared to the S­(SO 2 )–S­(MoS 2 ) interactions.…”

A Janus MoSSe monolayer: a superior and strain-sensitive gas sensing material

“…[7][8][9][10] However, the intrinsic metallic feature of graphene limited the respond sensitivity of gas sensors. [11][12][13][14] Therefore, the 2D layered materials with semiconducting behavior is highly desired for a gas sensor with outstanding preformances. The semiconducting 2D layers with tunable electronic properties by the light or gate bias is particularly attractive since the transport characteristics can be modulated to enhance sensing performance.…”

Near‐Room‐Temperature Ethanol Gas Sensor Based on Mesoporous Ag/Zn–LaFeO3 Nanocomposite

“…The O 1s spectrum in Figure f can be deconvoluted into two contributions, corresponding to two kinds of oxygen at the surface. The adsorbed oxygen species play a vital role in the gas sensing process of semiconductors by modulating the interaction with target gases . The peak around binding energy of 531.5 eV is ascribed to chemical absorbed oxygen (O A ) at the surface of composite .…”