Comparative theoretical study ofH2Seadsorption and dissociation onZnO(101¯0),TiO2(110), andZn2TiO4(010)

Abstract

Removal of corrosive or toxic species such as As, Se, and S is critical to the successful implementation of high efficiency integrated gasification combined cycle processes to utilize coal as a more environmentally friendly fuel. In this work we comparatively study the mechanisms of surface reaction of ${\text{H}}_{2}\text{Se}$ on a regenerable sorbent, zinc orthotitanate $({\text{Zn}}_{2}{\text{TiO}}_{4})$, and two constituent materials, ZnO and ${\text{TiO}}_{2}$, using first-principles density-functional theory. ${\text{H}}_{2}\text{Se}$ adsorbs more strongly on the $\text{ZnO}(10\overline{1}0)$ and ${\text{Zn}}_{2}{\text{TiO}}_{4}(010)$ surfaces than on the ${\text{TiO}}_{2}(110)$ surface. Investigation of the dissociation rates shows that dehydrogenation should be facile on both ${\text{Zn}}_{2}{\text{TiO}}_{4}$ and ZnO while it is much slower on ${\text{TiO}}_{2}$. Evaluation of sublimation energies of ${\text{Zn}}_{2}{\text{TiO}}_{4}$ and ZnO suggests that ${\text{Zn}}_{2}{\text{TiO}}_{4}$ has higher thermal stability than ZnO due to addition of ${\text{TiO}}_{2}$, in agreement with experimental results.