Abstract
Structure relaxation of monoclinic TeMo5O16 catalyst that exhibits two-dimensional semiconductive character has been controlled by ultralow doping content of vanadium Its roles in changing the redox abilities of the catalysts are first studied via experimental and theoretical methods. Strong O-Mo center dot center dot center dot O bond alteration occurs along the b direction both in bulk and on the surface. Meanwhile, the Mo-Mo distances and Mo-O-Mo angles are continuously changed as the degree of structural relaxation increases. As a result, the electron coupling and oxygen covalent bonding are remarkably weakened in the Mo4O18 unit The redistribution of Mo 4d electrons in the Mo4O18 unit forms the (Mo5+-O-Mo5+)/(Mo6+-O-Mo6+) redox sites as electron donor-acceptor and oxygen reservior. The presence of such redox sites is proved to sharply enhance the redox abilities of the catalysts by surface probe reactions.