Reactive trajectories for *CO–CHO formation at the high coverage of surface H (H* in 1 ML) from AIMD simulation at 298 K (A) one *CHO and one nonadsorbed CO, (B) transition state, and (C) *CO-CHO. The solvent water molecules are hidden for viewing convenience. The colors are Cu in orange, C in gray, H in yellow, and O in red. The reaction barrier is 0.71 eV.