First-principles study of O2 adsorption on Al-doped ZnO(10(1)over-bar0) surface

Understanding the O-2 adsorption on the Al-doped ZnO surface is crucial to unravel its enhanced sensing performances toward reducing gases (such as CO and H-2) compared with its undoped counterpart. We have studied the O-2 adsorption on the defect-free Al-doped ZnO(10 (1) over bar0) surface by using first-principles calculations. It is found that Al doping introduces electrons into the conduction band of the ZnO(10 (1) over bar0) surface, which should significantly enhance the conductance of the oxide. The adsorbed O-2 can effectively acquire electrons from the Al-doped ZnO(10 (1) over bar0) surface, leading to the decrease in the conductance of the materials. Upon gaining electrons, the adsorbed O-2 molecules on the Al-doped ZnO(10 (1) over bar0) surfaces exist in the form of superoxo O-2(-) species, which are expected to be chemically active toward reducing gases. (C) 2015 Elsevier B.V. All rights reserved.