Research on adsorption enhancement of formaldehyde over transition-sensitive carbon materials for fast purification

Abstract

In order to simultaneously purify indoor air and exchange no pollutants with outdoor atmosphere, the method of adsorption purification for formaldehyde is brought up and its enhancement mechanism over graphene is theoretically investigated in this study via density functional theory (DFT). The distribution of adsorption sites, relationship between adsorption sites and adsorption forms, effects of dopant atoms on adsorption features of HCHO as well as transfer of weakly-adsorbed structures to strongly-adsorbed ones are main research contents of this study. The simulation results indicate that pure graphene barely shows affinity to HCHO molecules owing to lack of polar surface electron distributed on the adsorbent. When Al atoms are inserted in the graphene to replace some C atoms, polar electronic centers are formed and they can get HCHO chemically adsorbed while HCHO can be only weakly adsorbed on adsorption sites far away from polar centers and hardly transferred to strongly-adsorbed forms. However, after both N and Al atoms are doped in graphene, not only can HCHO be intensely adsorbed on more sites, but weak physisorption can be more easily transitioned into strong chemisorption, which makes accessible strong-adsorption areas of doped graphene for HCHO larger. This research supplies helpful information for utilization of graphene series to accomplish indoor air purification.