▎ 摘　　要

We study the effect of different gas adsorbates (N-2, O-2, and CO2) on the field emission (FE) properties of graphene film. Our experimental measurements show that, except for N-2, adsorption of O-2 and CO2 reduces the FE current of the graphene film. Moreover, the measured FE hysteresis loop is almost quenched after adsorbing O-2 or CO2. The ab initio calculations quantify the experimental results by predicting a larger work function and smaller FE current for the graphene system after O-2 or CO2 adsorption. In contrast, the change of FE properties in N-2 adsorbed graphene is negligible. A "depolarization electric field model" is then proposed to explain the observed FE hysteresis behavior.