If you take urea (urine) and heat it at about 500-600 C, it becomes graphitic carbon nitride (melon). It turns out that this material is photocatalytic and may catalyze the hydrolysis of water. However, I think the reaction is too slow to be useful. However, I have been reading that if you take carbon nitride material amd then put it in an anerobic solution with an "electron donor", probably like methyl viologen/paraquat, that the paraquat will reduce blue and then may reduce hydrogen and carbon dioxide to methanol or methane. Also, chicken feathers can be heated and carburized and used to store hydrogen. Titanium dioxide doubles the photocatalytic activity of graphitic carbon nitride.