Abstract
• O 2 molecules bond with Sn atoms on the crystal plane and H 2 O molecules bond with Zn atoms to form characteristic adsorbed species. • As the characteristic adsorbed species, H 2 O molecules further promoted the natural adsorption of O 2 molecules in the form of hydrogen bond. • The crystal conductivity changes with the adsorption and desorption. • High temperature facilitates the adsorption of O 2 molecules. The molecular adsorption behavior of Zn 2 SnO 4 (1 1 1) crystal plane was studied. DFT theoretical simulation result shows that O 2 and H 2 O molecules are adsorbed on the crystal plane by bonding with Zn atom and Sn atom respectively and forming characteristic adsorption species. H 2 O molecules as characteristic adsorbed species promote the natural adsorption of O 2 molecules in the form of hydrogen bonds, N 2 molecules adsorb naturally in the form of physical adsorption. Meanwhile, the crystal surface conductivity varies with the adsorption and desorption of different gases. When the adsorbent is only O 2 molecule, the crystal surface conductivity decreases, the DOS of Fermi is from 8.00 to 4.01 electrons/eV. The conductivity of crystal surface increases when H 2 O molecule acts as a characteristic adsorbent and further adsorbs O 2 molecule, the DOS of Fermi is from 5.74 to 8.51 electrons/eV. When oxygen molecules are directly adsorbed on Zn 2 SnO 4 (1 1 1) crystal plane, the adsorption energy is +0.79 eV, while when oxygen molecules are further adsorbed on Zn 2 SnO 4 (1 1 1) crystal plane through water molecule, the adsorption energy is +2.71 eV. This conclusion was confirmed by EIS. In situ Raman spectroscopy detection of acetone molecule gas sensitive experiment showed that the adsorption of O 2 molecules is slow at room temperature and fast at high temperature, which is consistent with the calculation result that O 2 molecule belongs to endothermic adsorption. The results show that, through the method of combining experiment and theory, the influencing mechanism is analyzed, which effects of different gases on adsorption properties of crystal surfaces. This work provides guidance for optimizing catalytic and gas sensitive properties of materials and realizing controllable optimization of surface properties of materials.
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