Water-Splitting Methods

In addition to conventional, chemical water splitting methods there exist electrolytic water splitting and water splitting via thermal cycles and hybrid processes. Hydrogen production via chemical water splitting is based in conventional process technology on chemical redox reactions in which water essentially reacts with carbon or carbon monoxide. Probably the oldest method is the splitting of steam with metallic iron [7.1]: (7.1)$$ {H_2}O + Fe \to FeO + {H_2}\quad; \;\Delta {H^0} = - 9.20kJ/mol, $$followed by the reduction of iron oxide to metallic iron with carbon monoxide: (7.2)$$ FeO + CO \to Fe + C{O_2}\quad; \;\Delta {H^0} = - 31.9kJ/mol. $$