The role of Zn2+ dopants in the acid-basic catalysis on MgO(001) surface: Ab initio simulations of the dissociative chemisorption of R-O-R′ and R-S-R′ (R, R′=H, CH3, C2H5)

Publication date: July 2017
Source:Surface Science, Volume 661
Author(s): Carla G. Fonseca, Sérgio R. Tavares, Carla V. Soares, Bruno G. daFonseca, Fábio J.F.S. Henrique, Viviane S. Vaiss, Wladmir F. Souza, Sandra S.X. Chiaro, Renata Diniz, Alexandre A. Leitão
Ab initio calculations were performed to study the effect of the Zn²⁺ dopant on the reactivity and the catalytic activity of the MgO(001) surface toward molecular adsorption and dissociation reactions of the H2O, H2S, CH3CH2OH, CH3CH2SH and CH3SCH3 molecules. The electronic analysis showed that Zn²⁺ cation increased the reactivity of the surface locally. All molecules dissociate on both surfaces except for water and ethanol which only dissociate on the MgO:Zn(001) surface, confirming the increased reactivity in this surface. The ΔG° for the dissociation reactions of the CH3CH2SH and CH3SCH3 molecules on pure MgO(001) surface is positive in the entire temperature range. On the other hand, the ΔG° for H2S molecule is negative until 148.7°C. In the case of the MgO:Zn(001) surface, the CH3CH2SH molecule dissociates in the entire temperature range and, for H2S molecule, the dissociation is spontaneous until 349.7°C. The rate constants obtained for the dissociation reactions were very large because the reaction barriers are very low in both surfaces for all the studied molecules, except for CH3SCH3 molecule. The Zn-doped MgO(001) surface, besides being more reactive, presented a better catalytic activity than the MgO(001) surface for the dissociation of this molecule.

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