Ab initio Study of the Hydrogen Molecule on ZnO Surfaces

Abstract

We conduct first-principles total-energy density functional calculations to study the interaction of H2 on ZnO surfaces. Four surface models of Zn-terminated (0001)-, O-terminated (0001)-, $(10{\bar 1}0)-$, and $(2{\bar 1}{\bar 1}0)-$oriented ZnO planes in the presence of H2 are evaluated. The relative stability of four different surface models is examined as a function of the chemical potentials of oxygen and hydrogen. We find that only surfaces of O-terminated (0001)-oriented ZnO models exhibit active sites for the dissociation of H2, which in turn enables the formation of water from dissociative chemisorption of 2H on the O-terminated ZnO(0001) surface. The surface energy of O-terminated ZnO(0001) surface in the presence of water was found to be negative under the O-rich and H-rich condition. The findings agree with the experimental observations that ZnO epitaxial layers are easily etched by hydrogen at typical growth temperatures.

Ab initioStudy of Atomic Hydrogen on ZnO Surfaces

“…2(b), which is very similar to the interaction of H 2 with the O-terminated ZnO(0001) described in our previous work. 13) The above finding is also consistent with other DFT calculations which find that water can be obtained on the O-terminated ZnO(0001) surface under the O-and H-rich limit and hydrogen adsorption plays a major role for the stabilization of the (0001) plane. 14,15) In Fig.…”