During the spacecraft from geospace penetrating into the atmosphere, a plasma sheath can be formed around its external surface due to shock heating which subsequently leads the radio communications between the space vehicle and ground-based stations to interrupt, i.e. the blackout problem happens. Many techniques have been developed to mitigate the blackout problem, and the attachment chemicals releasing is considered as an effective method. Previously, halogenides and water have been widely investigated both theoretically and experimentally. In this work, we report the mitigation of the reentry plasma sheath through releasing carbon dioxide, in which the electron density is reduced through different mechanisms and processes from the releasing halogenides. Controlled experiments are performed to investigate the carbon dioxide released in the arc wind tunnel and the high-frequency plasma wind tunnel. Results suggest that the electron density can be significantly reduced in the simulated plasma sheath environment, which provides a potential approach to solving the communication blackout problem encounterin the reentry process.