Pd掺杂ZnO(0001)表面的气敏机理

Gas Sensing Mechanism of the Pd-Doped ZnO(0001) Surface

利用基于密度泛函理论(DFT)的第一性原理研究了O原子与Pd掺杂前后ZnO(0001)表面的相互作用机理。通过对模型表面六个高对称位吸附能的计算,发现O原子最有可能吸附于Pd掺杂表面的间隙位。从表面的态密度(density of states,DOS)及分波态密度(partial density of states,PDOS)分析结果可以看出,掺杂体系中费米能级附近出现的杂化峰是由O原子的p轨道电子和Pd原子的d轨道电子杂化引起的。掺杂表面的差分电荷密度反映出O原子与Pd原子之间存在大量电荷转移,说明掺入催化剂Pd有助于提高ZnO材料的气敏性能。最后,通过对挥发性有机化合物(VOC)气体的气敏测试验证了理论计算的结论。

The interaction mechanism between the oxygen atom and pure/Pd-doped ZnO （0001） surface was studied by using the first principles based on the density functional theory （DFT）. The adsorption energies of six highly symmetric adsorption sites in the model were calculated re- spectively. The results show that the oxygen atom prefers to be adsorbed on the hollow site of Pd-doped ZnO （0001） surface. The analysis results of the density of states （DOS） and partial density of states （PDOS） indicate that the electron hybridization between p orbit of O and d orbit of Pd leads to a new hybrid peak near the Fermi level in the doped system. The electronic density difference of Pd-doped ZnO （0001） surface shows that there is a significant charge transfer be- tween the O and Pd atoms, which proves that the catalyst of Pd helps to improve the gas sensing properties of ZnO. Finally, the conclusions based on the theoretical calculation were verified by gas sensing experiments of volatile organic compounds （VOC）.