Adsorption of sulfuric acid on graphene with a high titanium coverage and on the [001] titanium surface

Surface Science, Volume 618, December 2013, Pages 36-41.

I. Carrilloa, E. Rangelb, J.M. Ramírez-de-Arellanob, L.F. Maganab.

 

aInstituto Tecnológico de Tláhuac, Av. Estanislao Ramírez # 301, Colonia Ampliación Selene, C.P. 13420 México, D.F., México and

bInstituto de Física, Universidad Nacional Autónoma de México, Apartado. Postal 20-364, C.P. 01000, México, D. F., México

 

Abstract

 

Density functional theory and molecular dynamics were used to study the adsorption of sulfuric acid on two surfaces. One is graphene modified with titanium with high metal coverage (C2Ti). The other is a [001] titanium surface. We considered cis and trans molecule conformers at 300 K, and atmospheric pressure. We found that the molecule (trans and cis) is dissociated and chemisorbed on the graphene–titanium layer, in several ways, forming a conductor surface. We also found that the molecule (cis and trans) is dissociated on the [001] titanium surface in only one, but a different way. In this case, all four oxygen atoms are chemisorbed, forming titanium oxide (TiO). The remaining sulphydric acid is physisorbed, and it desorbs at 700 K.

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Significance Statement

We used density functional theory and molecular dynamics to study the adsorption of sulfuric acid on two surfaces. One is graphene modified with titanium with high metal coverage (C2Ti). The other is a [001] titanium surface. We considered cis and trans molecule conformers at 300 K, and atmospheric pressure. The sulfuric acid molecule is adsorbed and dissociated in several ways on a graphene-titanium surface with a high metal coverage. The same molecule is adsorbed and dissociated in only one, but a different way on a [001] titanium surface.

On the graphene-titanium surface, the molecule is dissociated into two or into three parts. In the first case, the adsorption energy is -0.67 eV. In the second case, the adsorption energy is -1.13 eV. It is important to mention the fact that this system remains as a conductor, after adsorption of sulfuric acid, unlike common sulfated oxides.

On the [001] titanium surface, we found that the molecule is adsorbed and dissociated during its interaction with the surface. It loses all oxygen atoms, which end bound to titanium atoms of the surface, forming titanium oxide (TiO). The resulting surface remains as a conductor. The remaining H2S is physisorbed. For all the initial orientations of the molecule, we found the same result (see figures 7 and 8). The adsorption energy is -5.1 eV. The sulfhydric acid desorbs at 700 K.  

We must mention that we could not find neither theoretical nor experimental results on the adsorption of sulfuric acid on titanium, or on the graphene-titanium system.

titanium surface

 

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