First-principles study of O2 adsorption on Al-doped ZnO(1 0 1¯ 0) surface

• The O2 adsorption on the Al-doped ZnO(1 0 1¯ 0) surface has been studied.
• Al doping can significantly increase the conductance of the ZnO(1 0 1¯ 0) surface.
• The adsorbed O2 can effectively acquire electrons from the Al-doped ZnO(1 0 1¯ 0) surface.
• The adsorbed O2 on the Al-doped ZnO(1 0 1¯ 0) surface exist in the form of superoxo O2–.

Understanding the O2 adsorption on the Al-doped ZnO surface is crucial to unravel its enhanced sensing performances toward reducing gases (such as CO and H2) compared with its undoped counterpart. We have studied the O2 adsorption on the defect-free Al-doped ZnO(1 0 1¯ 0) surface by using first-principles calculations. It is found that Al doping introduces electrons into the conduction band of the ZnO(1 0 1¯ 0) surface, which should significantly enhance the conductance of the oxide. The adsorbed O2 can effectively acquire electrons from the Al-doped ZnO(1 0 1¯ 0) surface, leading to the decrease in the conductance of the materials. Upon gaining electrons, the adsorbed O2 molecules on the Al-doped ZnO(1 0 1¯ 0) surfaces exist in the form of superoxo O2− species, which are expected to be chemically active toward reducing gases.