They've commited to ordering 100k electric vans from Rivian:
"Amazon CEO Jeff Bezos said the company has placed an order for 100,000 electric delivery vans from Michigan-based startup Rivian. The announcement came during an event on Thursday in Washington, DC where Bezos unveiled Amazon’s sweeping plan to tackle climate change."
https://www.theverge.com/2019/9/19/20873947/amazon-electric-...
This was part of their investment into Rivian:
"In February 2019, Amazon announced it would be leading an investment round of $700 million into Rivian." https://en.wikipedia.org/wiki/Rivian