Herman, 38, will make his first Open Championship appearance. He earned his maiden PGA Tour victory earlier this season at the Shell Houston Open, and will now play in all four majors in 2016 after making only three total major championship starts prior to this year.
Hurley earned the spot as part of the Open Qualifying Series with his breakthrough win Sunday at the Quicken Loans National. He opted to withdraw on Tuesday and will instead be with his sister, Megan, when she gets married in Virginia on July 16, the same day as the third round at Troon.
Herman is ranked No. 80 in the world and was the top name on the alternate list based on the world rankings of those not already qualified.
Five more spots in the Open will be secured this week: four players not already qualified among the top 12 finishers at the Open de France, plus the top finisher not already qualified among the top five at the PGA Tour's Barracuda Championship.
The Open Championship will be held July 14-17 in Ayrshire, Scotland.