Facebook CFO David Wehner has joined the board of Alector, a biotech company that is working to develop treatments for Alzheimer's disease.

This is the first time that Wehner has joined a board outside of Facebook since he took the job in 2014. He previously served on the board of StubHub.

It might seem like an unusual choice for Wehner, whose career has spanned technology and finance, rather than health care. But his predecessor, David Ebersman, followed a similar path, leaving Facebook to start a mental health company called Lyra Health. Ebersman also had a background in biotech.

The appointment comes at a time when employee morale at Facebook has plunged. A recent internal survey reportedly found that 52 percent of employees were optimistic about the company's future, down from 84 percent a year ago.

Wehner isn't the only executive at the company to seek opportunities outside of his day job.

Facebook's CEO Mark Zuckerberg takes a break every quarter to hear from scientists from the Chan Zuckerberg Biohub talk about their research. (Zuckerberg is one of the largest investors in the Biohub and he serves on its board alongside his wife, Priscilla Chan, and LinkedIn founder Reid Hoffman.).