Herrmann had the first meaningful effort of the game on the quarter-hour mark when he lashed towards the corner but couldn't get the better of Ralf Fahrmann.
The only goal of the game arrived 10 minutes before the break when Herrmann smacked a first-time shot into the corner after running onto Raffael's centre.
Max Kruse could have put Borussia further in front after half time but his effort went just wide of the post.
Schalke were inches away from an equaliser nine minutes from time when Adam Szalai's shot came back off the post.
Victory for Borussia sees them move into the European spots, with Schalke still third going into the final two games of the season.