H₂O, NO_x Molecules Are Adsorbed On Cu, Co Doped ZnAl₂O₄ Spinel Low First-principles Study Of Exponential Surface

Spinel-type oxide ZnAl₂O₄ has promising physical and chemical properties,which widely used in transparent conductive material,catalyst,catalyst support and radiation resistant material.Transition-metal supported ZnAl₂O₄ used as a favorable heterogeneous catalyst,it has wide application in photocatalytic organic dye,organic synthesis,and hydrocarbon selective catalytic reduction of NO_x.The structure and properties of the low-index Zn Al₂O₄ surface?100?,?110?and?111?based on density functional theory calculations.Correlation between surface structure and adsorption behavior of H₂O,NO,and NO₂ on ZnAl₂O₄ low-index surfaces was established.Cu/Co-doped ZnAl₂O₄ low-index surface?100?,?110?and?111?was established.NO and NO₂ adsorption performance on Cu/Co-doped ZnAl₂O₄ low-index calculated.The effect of existing H₂O and O₂ molecules on HC-SCR NO₂ over Co-doped ZnAl₂O₄?111?surface was calculated.The results of calculations support theoretical guidance for studying surface structure of ZnAl₂O₄and spinel species oxides and design and preparation catalyst.The main research contents and results are as follows:When termination layer was Zn-O-Al,ZnAl₂O₄?100?,?110?and?111?surface had lowest surface energy.The protruding and coordination unsaturated Zn_2c and Al_3cc sites can act as adsorption sites for gas molecules.Al_3c sites of ZnAl₂O₄?111?surface had energy level on Fermi level,which can hybridize and overlay with the molecular orbital of H₂O,NO,and NO₂ enhanced adsorption stability.H₂O molecule absorbed on ZnAl₂O₄ low-index surface was the structure-sensitive process.H₂O molecule easily absorbed on Zn and Al sites which protruding termination layer.H₂O molecule absorbed on ZnAl₂O₄ low-index surfaces generated hydrogen bond and formed molecular multiple rings greatly enhanced adsorption stability.H₂O dissolved on ZnAl₂O₄?111?surface into a hydroxy and an H atom through surface sites Al_3c-O_3c or Al_3c-Zn_3c.Cu/Co-doped in ZnAl₂O₄ low-index surfaces decreased the surface energy.Doping of Cu and Co improved adsorption performance of NO and NO₂ over ZnAl₂O₄ low-index surfaces,and doping of Co was more notable.NO and NO₂generated double-bond and single-bond on ZnAl₂O₄ low-index surfaces,generation of double-bond was more stable.The electronic state of Cu 3d/Co 3d and Zn 3d existed synergy effect,hybridizing and overlaying with the molecular orbital of NO and NO₂,provided driving force for NO and NO₂ molecules adsorbed on ZnAl₂O₄ low-index surfaces.Al_3c sites of?111?surface generated an energy level on Fermi level can hybridize and overlay with molecular orbital of NO and NO₂,providing extra driving force for adsorption of NO and NO₂ molecules.When existing of O₂ and H₂O on adsorption system of C₂H₄-SCR-NO₂ over Co_0.25Zn_0.75Al₂O₄?111?,H₂O and O₂ made the adsorption system more stable,NO₂,C₂H₄,H₂O and O₂ molecules existed synergetic mechanism,charges transformed form Co_0.25Zn_0.75Al₂O₄?111?into gas molecules.