Cu/Ag单掺及Cu-Ag共掺对ZnO光催化性能影响的第一性原理研究

The stability, electronic structure and optical properties of ZnO with Cu/Ag doped and Cu-Ag codoped were studied by first-principles method. Formation energies of Cu_Zn2 and Cu_Zn1-Cu_Zn3 are close to 0.0 eV, and negative for Cu_Zn1-Cu_Zn2, which indicates that Cu doped is effortless and tends to gather. The value for Ag_Zn2 is 2.5 eV, and higher than 4.5 eV for Ag_Zn1-Ag_Zn2 and Ag_Zn1-Ag_Zn3. It's difficult for Ag doping with higher concentration. Formation energies of Cu_Zn1-Ag_Zn2 and Cu_Zn1-Ag_Zn3 are close to that of Ag_Zn2. The Cu3d and O2p states have obvious hybridization in models of Cu_Zn2, Cu_Zn1-Cu_Zn2 and Cu_Zn1-Cu_Zn3, the top of valence band is mainly occupied by Cu3d states. The hybridization between Ag4d and O2p states for Ag_Zn2, Ag_Zn1-Ag_Zn2 and Ag_Zn1-Ag_Zn3 models is weaker, the top of valence band is mainly occupied by O2p states. For Cu_Zn1-Ag_Zn2 and Cu_Zn1-Ag_Zn3 models, although Cu3d states hybridize with O2p states, the top of valence band is mainly occupied by O2p states. Cu/Ag doped and Cu-Ag codoped lead Zn4s states downward significantly, which reduces the band gap of above models. They influence the electronic structure of ZnO near the band gap mainly. The modified ability of Cu-Ag codoped to ZnO electronic structure is between Cu/Ag doped ZnO. The absorption edges of above models have obvious red-shift, which realizes the visible light absorption for ZnO. The ultraviolet light absorption also is higher than pure ZnO in the range of 3.10-3.90 eV. Cu/Ag doped and Cu-Ag codoped improves the photocatalytic activity of ZnO. According to formation energy analysis, the models with higher photocatalysis under different doping are Cu_Zn1-Cu_Zn2, Ag_Zn2 and Cu_Zn1-Ag_Zn2.