Adsorption of ammonia on ZrOx-modified graphene nanoribbon: a first-principle investigation

Ammonia (NH3) is a main environmental pollutant related to global warming, and reduction of its emission is the subject of multiple international agreements and regulations. Accordingly, the development of highly precise detectors to monitor its content in the environment is essential to track and limit its emission. This work examines the influence of modifying of armchair–graphene nanoribbon (AGNR) by zirconium (Zr) and its oxides on its adsorption for NH3 gas. Density functional theory (DFT) computations are utilized to investigate the band structure, adsorption energy (Ed\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${E}_{d}$$\end{document}), adsorption length (D\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$D$$\end{document}), charge transferred (ΔQ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta Q$$\end{document}), and density of states (DOS) of pristine and modified structures with ZrOx (x=0,1,or2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$x=0, 1, \mathrm{or }2$$\end{document}). ZrOx is presented to AGNR nanostructure by two pathways: substitution of carbon atoms (doping) and introduction on top of the AGNR surface (decoration). The findings of the investigation illustrate great improvement of NH3 adsorption on AGNR due to its modification. Although the adsorption energy is enhanced in general upon modification, AGNR structures where ZrOx substitute carbon atoms exhibit greater adsorption energy as compared with the decoration scheme. The maximum energy of adsorption is for the AGNR structure doped with ZrO2, followed by that doped with Zr. The adsorption energy of NH3 on the ZrO2-doped AGNR is − 10.05 eV with an adsorption length of 2.4 Å and − 0.214e charge transferred. As compared to the pristine structure, the adsorption energy for NH3 on AGNR doped with ZrO2 increases 22.2 times. Therefore, AGNR nanostructure doped with ZrOx can be considered for practical sensors for the applications of detection and control of ammonia emission.