Hydrogen adsorption on β-Ga2O3(1 0 0) surface containing oxygen vacancies

Abstract

The understanding of hydrogen (H) adsorption on gallia is an important step in the design of molecular sensors and alkane dehydrogenation–aromatization catalysts. We have simulated the (100) surface of b-Ga2O3, which is the more frequent cleavage plane. Our study has considered oxygen vacancies in that plane. We have used the atom superposition and electron delocalization molecular orbital (ASED-MO), a semiempirical theoretical method, to understand both the electronic and bonding characteristic of H on b-Ga2O3 surface. As a surface model, we have considered both a cluster and a five-layer slab. We have found that H adsorption occurs on Ga sites close to oxygen vacancies. Two types of Ga have also been considered; namely, Ga(I) and Ga(II), with different coordination: Ga(I) is fourcoordinated and Ga(II) six-coordinated. The Ga(I)–H bond is aprox 24% stronger than Ga(II)–H while Ga(I)–O(I) bond is aprox 44% stronger than Ga(II)–O(I). Also, Ga(I)–O(III) is aprox 56% stronger that Ga(II)–O(III). The Ga–H and Ga–O interactions are always bonding. The Ga–Ga overlap population is null. We have assigned the 2003 and 1980cm -1 infrared bands to the stretching frequencies of Ga(I)–H and Ga(II)–H bonds, respectively.