At about 8:21pm, Larry Moss ordered agent Powell to handcuff Jack Bauer, after the raid on the White House, because of his illegal interrogation of Ryan Burnett.
Later, Powell was among the 25-agent team—led by Renee Walker and Park—which raided the abandoned building at 1297 Rincon in the search for Robert Galvez. He was inside when the building was gutted by Galvez's C4 explosions at about 2:47am.
Background information and notes
The name "Powell" is seen on the FBI map (see this image) during Day 7: 2:00am-3:00am. The character may not actually appear on-screen during this episode. It was not specified if Powell survived or was among those agents killed in the blasts.