Hydrogen adsorption on the b-Ga2O3(100) surface containing oxygen vacancies

ESTELA A. GONZALEZ; PAULA V. JASEN; ALFREDO JUAN; SEBASTIÁN E. COLLINS; MIGUEL A. BALTANÁS; ADRIAN L. BONIVARDI

SURFACE SCIENCE

Año: 2005 vol. 575 p. 171 - 180

0039-6028

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 ~24% stronger than Ga(II)–H while Ga(I)–O(I) bond is ~44% stronger than Ga(II)–O(I). Also, Ga(I)–O(III) is ~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.