Rh- and Ru-Modified InSe Monolayers for Detection of NH3, NO2, and SO2 in Agricultural Greenhouse: A DFT Study

The level of agricultural greenhouse intelligence is an important indicator of national agricultural modernization. Thus, it is important to achieve the detection of characteristic gases in the greenhouse to maintain the growth of crops. In this paper, NH3, NO2, and SO2 are the target detection gases in the greenhouse. The adsorption models of rhodium-doped indium selenide (Rh–InSe) and ruthenium-doped indium selenide (Ru–InSe) for the three characteristic gases were established based on density functional theory (DFT). By analyzing the adsorption energy, density of states, and deformation charge density of the two modified systems compared to the intrinsic InSe, it was found that the introduction of metal atoms effectively opened the energy gap of the intrinsic InSe and exhibited strong chemisorption. Finally, two gas-sensitive materials, Rh–InSe and Ru–InSe, are analyzed by comparing them in terms of frontier molecular orbital theory and desorption time. It can be seen that the adsorption energy of the Rh–InSe system is all higher than that of the Ru–InSe system, but Ru–InSe has higher conductivity and shorter desorption time than Rh–InSe and also exhibits stable chemisorption. By calculating the sensitivity of Rh and Ru–InSe, it can be found that Ru–InSe is more sensitive to the characteristic gas, which is favorable for gas adsorption. Therefore, Rh–InSe is more suitable as an adsorbent for three harmful gases, and the Ru-modified InSe monolayer has potential applications in the field of materials for realizing the detection of characteristic harmful gases in a greenhouse.