Mitch there are lots, easily found on Google, this one is from a government study: https://www.nrel.gov/docs/fy02osti/32405b25.pdf

But we should note the Chinese are streets ahead of us, their research though public, is behind the language and political firewall, but we can see actual products routinely for for sale in Alibaba, which can be used to do the job. Reversible fuel cell functionality is obtainable by using an electrolyser with storage tank in conjunction with a standard fuel cell, by connecting the hydrogen and electrical ports of each together, using some clever circuitry to determine when the combination is being charged, and when it is being discharged.

I have been engaged in modeling these combinations for the past three or four months, there are standard modeling blocks in system modeling toolsets (Matlab/Simulink), I am a long practicing Systems Engineer with this background, so I see possible requirement to provide some guidance in use of the technology, as soon as I feel proficient... (not yet!), I will publish some results in Medium.