Theoretical Study into Adsorption of \NO_x\ and \CO_x\ by Single Atom Cobalt Adsorbent
Hafiz Aji Aziz(a), George Enrique Sanjaya(a)

a) Departement of Chemistry, Universitas Pendidikan Indonesia, Bandung 40154, Indonesia

Abstract

Industrial processes generate nitrogen oxides (NOx) and carbon oxides (COx) emissions, contributing to air pollution and environmental damage. Mitigating these emissions requires efficient adsorbent materials, but experimental studies are often costly and time-consuming. This work utilized density functional theory (DFT/B3LYP/LANL2DZ) calculations in ORCA to predict the thermodynamics and structural properties of NOx and COx adsorption on a single-atom cobalt adsorbent. Four gas species (NO, NO&#8322-, CO, CO&#8322-) were evaluated in different binding conformations to provide a comprehensive understanding of adsorption performance. For NO, both N-bond (NO) and O-bond (ON) configurations were studied, yielding &#916-G = -75.19 kJ/mol for NO vs. -66.29 kJ/mol for ON. NO&#8322- was examined in N-bond (NO&#8322-) and O-bond (O&#8322-N) orientations, with &#916-G = -117.33 kJ/mol and -122.95 kJ/mol, respectively. CO binding was compared for C-bond (CO, &#916-G = -63.84 kJ/mol) and O-bond (OC, &#916-G = -46.70 kJ/mol). CO&#8322- adsorption was similarly evaluated for C-bond (CO&#8322-, &#916-G = -41.40 kJ/mol) and O-bond (OCO, &#916-G = -47.91 kJ/mol) modes. Structural analysis reveals bond lengths from 1.348 (NO&#8322-) to 1.868 (CO) and cobalt charge distributions from 0.1512 (CO&#8322-) to 0.3424 (ON). The adsorption strength follows O&#8322-N > NO&#8322- > NO > ON > CO > OCO > CO&#8322-, with NOx species showing the strongest interactions. These results indicate that the single-atom cobalt adsorbent should be considered for further studies, especially using experimental methods.

Keywords: density functional theory, single-atom cobalt, \NO_x\ adsorption, \CO_x\ adsorption, binding conformations, thermodynamics.

Topic: Chemistry and Chemistry Education