Yes. Assuming the sacrificed creature is a Zombie, Diregraf Captain's ability will cause target opponent to lose 1 life. This is because "dies" simply means "goes to the graveyard from the battlefield".

Is sacrificing a creature dying?

Yes you can . Dying is a keyword that means going from the battlefield to the graveyard. This includes sacrifice.

What does sacrifice a creature mean?

Description. Sacrificing or saccing is purposely or forcefully removing a permanent from play. This can be due to an effect on the card itself, the effect of another permanent already in play, coming into or leaving play or a spell such as an instant or sorcery. A sacrificed permanent cannot be regenerated.