Mechanism for NiAl-LDH/Graphene Oxide Heterojunctions Absorbing HCl: A First-Principles Study

Layered double hydroxide (LDH), graphene and their heterojunction can adsorb hydrogen chloride (HCl) released during the pyrolysis of polyvinyl chloride (PVC). But the mechanism is not clear. To investigate the adsorption mechanism and inform the development of high-performance HCl adsorbents and PVC heat stabilizers, this paper established heterojunction models of NiAl-LDH/graphene (LDH/G) and NiAl-LDH/graphene oxide (LDH/GO). It analyzed electronic properties, adsorption orientation, sites, and capacity of HCl on the LDH/G heterojunction by first principles. The most stable adsorption structure is the HCl molecule perpendicular to the G plane, with Cl near the G plane at distance of 3.519 Å, and the adsorption energy is −0.328 eV. LDH/GO heterostructure has excellent adsorption capacity. Among them, LDH/GO with epoxy groups in graphene demonstrates the highest adsorption stability, with an adsorption energy of −0.878 eV. Differential charge density plots show that the structure has the most electron transfer. The partial density of states and total density of states reveal charge transfer occurring during the hybridization and adsorption processes involving the Ni-3d, C-2p, O-2p, and Cl-3p orbitals. The maximum number of adsorbed HCl for the structure is 11 by molecular dynamics simulation. Therefore, LDH/GO heterojunction is a promising material for the adsorption of HCl.