Density Functional Theory Investigation into the B and Ga Doped Clean and Water Covered γ-Alumina Surfaces

Lihong Cheng,Zehua Zhou,Jianping Ai,Tianliang Xu,Zhiqin Chen,Jianwen Liu,Wenkui Li

doi:10.1155/2017/6215315

Abstract

The structures and energies of the B and Ga incorporated γ-alumina surface as well as the adsorption of water are investigated using dispersion corrected density functional theory. The results show that the substitution of surface Al atom by B atom is not so favored as Ga atom. The substitution reaction prefers to occur at the tricoordinated A(4) sites. However, the substitution reaction becomes less thermodynamically favored when more Al atoms are substituted by B and Ga atoms on the surface. Moreover, the substitution of bulk Al atoms is not so favored as the Al atoms by B and Ga on the surface. The γ-alumina surface is found to have stronger adsorption ability for water than the B and Ga incorporated surface. The total adsorption energy increases as water coverage increases, while the stepwise adsorption energy decreases. The studies show the coverage of water at 7.5 H2O/nm2 (five H2O molecules per unit cell) can fully cover the active sites and the further water molecule could only be physically adsorbed on the surface.

Highlights

The γ-alumina is an important material in chemistry and materials science due to its widespread applications in chemical industry [1,2,3], ceramics, and semiconductors [4,5,6,7]
The substitution of surface Al3+ by Fe3+ in alumina with mixed (Al1−xFex)2O3 surface formation is confirmed by transmission Mosbauer spectroscopy
Integral low-energy electron Mosbauer spectroscopy and Fe K-edge X-ray absorption near-edge structure characterization observed the formation of iron nanoclusters from the transformation of γ-(Al1−xFex)2O3 to α-(Al1−xFex)2O3 and the iron distribution on the surface layers and in the cores of grains [12,13,14]

Summary

Introduction

The γ-alumina is an important material in chemistry and materials science due to its widespread applications in chemical industry [1,2,3], ceramics, and semiconductors [4,5,6,7]. Integral low-energy electron Mosbauer spectroscopy and Fe K-edge X-ray absorption near-edge structure characterization observed the formation of iron nanoclusters from the transformation of γ-(Al1−xFex)2O3 to α-(Al1−xFex)2O3 and the iron distribution on the surface layers and in the cores of grains [12,13,14]. This field attracts the interests of theoretical researches. Since γ-alumina is usually prepared and used in atmospheres containing water, the adsorption of water on the B and Ga incorporated γ-alumina is investigated and compared with the water adsorption on pure γ-alumina surface

Computational Details

Results and Discussion

Conclusions