Very cool research. On the topic of hydrogen deep underground: I'm not an expert, just a fascinated amateur, but I've been fascinated by the recent discovery that there is enormous amounts of hydrogen below the earth. In fact, this article mentions hydrogen forming by serpentinization, and says that the researchers were shocked to find so much hydrogen. Recent research indicates that hydrogen may exist deep in the earth from processes other than serpentinization as well. There are now a handful of companies working to extract this natural hydrogen to use as a source of green energy. Exciting stuff.

This is an excellent research overview on the topic of "natural" geologic hydrogen https://www.sciencedirect.com/science/article/abs/pii/S00128...

I've also compiled some of my own notes on that paper here which provide some summaries on the multiple fascinating sub-topics. (E.G. hydrogen may be a driver of earthquakes! And we may be able to use hydrogen samples to predict earthquakes! Some predict that there may be even more biomass under the earth driven by sources like hydrogen and methane than there is above ground!) https://docs.google.com/document/d/1pnW4HRq6E2up0DhIoxjCyGS6...