First-principle study of O vacancy on LaNiO3 (001) surface

In the paper, based on the first principle of density functional theory, it is easier to form O vacancy on the surface by calculating vacancy formation energy, from which the adsorption problems of H-2 molecule on LaNiO3 (001) surface with O vacancy are calculated and analyzed. By calculating the adsorption energy and dissociation energy of LaNiO3 (001) surface with O vacancy, it is found that there are two kinds of chemical adsorption modes on the surface of LaNiO3 (001):The first one is that two H atoms are adsorbed to the same O atom to form H2O molecules, which is the best adsorption position where the PBE and PBESOL functionals are applied to perform geometry optimization and property analysis, and it is found that the application of PBESOL functional is less ideal than the application of PBE functional and takes longer. At this point, the effects of H and O atoms result from the orbital hybridization effects of H 1s and O 2p, and there is a typical covalent bond between H and O. The second one is that two H atoms are respectively adsorbed to the two O atoms, forming two OH groups. Furthermore, H-2 molecules on the surface of LaFeO3 (010) can also set off physical adsorption. The results show that the existence of O vacancy will lead to the increasing of adsorption energy of H, which is easier to reserve hydrogen; it also will reduce the conductivity of the surface, however, the surface conduction band with O vacancy will increase after absorbing H and its electrical conductivity will be enhanced; to appropriately increase the quantity of O vacancy of the surface will accelerate the decomposition of H-2, but it does not have much effect on the electrical conductivity of the surface. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.