Advanced direct use of geothermal energy for hydrogen production and material conversion

Production of hydrogen by using geothermal energy was investigated. Georeactor is one of advanced direct use for chemical reactions to produce hydrogen and material conversion. Hydrogen sulfide (H ₂S, HS ^- and S ^2-) has great potential to produce hydrogen under hydrothermal condition, however, oxidized sulfur species such as SO ₄ ^2- and S ₂O ₃ ^2- were produced as by-product of generation of hydrogen. Some of organic compounds and urea had possibilities to reduce oxidized sulfur species into reduced sulfur species to reproduce hydrogen. We carried out hydrothermal experiments involving two reaction steps which were production of hydrogen and reduction of sulfur oxidized species. We can obtain over 40% conversion rate to produce hydrogen under hydrothermal condition by using the lab-scale georeactor.