  The role of catalyst support and regioselectivity of molecular adsorption on
a metal oxide surface is investigated for the NO reduction on a
Cu/{\gamma}-alumina heterogeneous catalyst. For the solid surface,
computational models of the {\gamma}-alumina surface are constructed based on
the Step-by-Step Hydrogen Termination (SSHT) approach. Dangling bonds, which
appear by cutting the crystal structure of a model, are terminated stepwise
with H atoms until the model has an appropriate energy gap. The obtained SSHT
models exhibit the realistic infrared (IR) and ultraviolet-visible (UV/Vis)
spectra. Vibronic coupling density (VCD), as a reactivity index, is employed to
elucidate the regioselectivity of the Cu adsorption on the {\gamma}-alumina and
that of the NO adsorption on the Cu/{\gamma}-alumina in place of the frontier
orbital theory that could not provide clear results. We discovered that the
highly dispersed Cu atoms are loaded on Lewis-basic O atoms, which is known as
anchoring effect, located in the tetrahedral sites of the {\gamma}-alumina
surface. The role of the {\gamma}-alumina support is to raise the frontier
orbital of the Cu catalyst, which in turn gives rise to the electron
back-donation from the Cu/{\gamma}-alumina to NO. In addition, the penetration
of the VCD distribution of the Cu/{\gamma}-alumina into the {\gamma}-alumina
support indicates that the excessive reaction energies dissipate into the
support after the NO adsorption and reduction. In other words, the support
plays the role of a heat bath. The NO reduction on the Cu/{\gamma}-alumina
proceeds even in an oxidative atmosphere because the Cu-NO bond is strongly
bounded compared to the Cu-O2 bond.

Materials Science