The most common way of producing hydrogen is steam reforming from natural gas.
The Sun (2009)
In overheated reactors, water can react with zirconium to produce hydrogen.
Times, Sunday Times (2011)
Chlamydomonas can reach anoxia and produce hydrogen at low light intensity.
Neda Fakhimi, Omid Tavakoli 2019, 'Improving hydrogen production using co-cultivation of bacteria with Chlamydomonas reinhardtii microalga', Materials Science for Energy Technologies