Energy Insights on Dissociative Chemisorption of (H 2 $$ {}_2 $$ O) n = 1 , 2 , 3 $$ {}_{n=1,2,3} $$ on Rutile-TiO 2 $$ {}_2 $$ (110)

Abstract

In this work, dissociative chemisorption of (H${\hspace{0.17em}}_2$O)${\hspace{0.17em}}_n$, $n=1,2,3$, on Rutile(R)-TiO${\hspace{0.17em}}_2$(110) was systematically studied by computing initial-geometry-specific potential energy curves (PECs) through the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. Due to orientational hydrogen-bonding interactions, (H${\hspace{0.17em}}_2$O)${\hspace{0.17em}}_n$ adsorbs on oxygen sites if it approaches to surface with the appropriate conformation. In general, the water molecule preferentially chemisorbs on the five-fold titanium atom (Ti${\hspace{0.17em}}_{5c}$) but never adsorbs on the six-fold one (Ti${\hspace{0.17em}}_{6c}$), while the second water molecule again preferentially chemisorbs on the nearest Ti${\hspace{0.17em}}_{5c}$ atom. This is consistent with experimental measurements (Chem. Soc. Rev. 45 (2016), 3701 and Chem. Rev. 119 (2019), 11020). Moreover, PECs for the dissociations of various O-H bonds are computed. The dissociation barriers with $n=1,2,3$ imply that dissociation ability increases with the increase of $n$. This is different from experiments on photon-dissociation (Chem. Rev. 119 (2019), 11020) which experimentally indicated that water dimer (i.e., $n=2$) has the largest photon-dissociation probability. This discrepancy between calculation and experiment implies the necessity of non-adiabatic quantum dynamics based on new potential energy surfaces, because the previous experiments focused on the photon-dissociation of (H${\hspace{0.17em}}_2$O)${\hspace{0.17em}}_n$ on R-TiO${\hspace{0.17em}}_2$(110) with $n=1,2,3$. Based on the present PBE calculations, discussions on previous experiments and calculations are also given.