Catalytic Activity of Au and Au2 on the h-BN Surface: Adsorption and Activation of O2

The structural, electronic, and catalytic properties of Au and Au-2 supported on the pristine and defected hexagonal boron nitride (h-BN) surface have been studied theoretically using density functional theory. It is demonstrated that adsorption and catalytic activation of O-2 on the h-BN supported Au and Au-2 can be affected by the interaction with the support via electron pushing and donor/acceptor mechanisms. It is shown that even weak interaction of Au and Au-2 with the defect-free "inert" h-BN surface can have an unusually strong influence on the binding and catalytic activation of the molecular oxygen. This effect occurs due to the mixing of the 5d orbitals of the supported Au and Au-2 with the N-p(z) orbitals. Although the defect-free h-BN surface does not act as a good electron donor for the supported O-2-Au, it promotes an electron transfer from the Au to O-2, pushing electrons from the gold to the adsorbed oxygen. In the case of the defected h-BN surface, Au and Au-2 can be trapped effectively by N or B vacancy and impurity point defects. Strong adsorption on the surface defects is accompanied by the large charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported Au and Au-2 can considerably promote their catalytic activity. Therefore, the h-BN surface (pristine or defected) cannot be considered as an inert support for Au and Au-2.