Hydrogen production from water: past and present

Hydrogen derived from sustainable materials may be an important energy vector in a post petroleum economy. The focus of this short review article is on the most studied methods for making hydrogen from water including: electrocatalytic, photocatalytic, and thermally driven reactions on reducible oxides. Hydrogen from renewables comes at a cost. Therefore, projected process cost issues are necessary in determining the best path forward. The most important challenge in the thermally driven reaction is finding a metal oxide that can be reduced at practical temperatures with acceptable reaction kinetics while the most important challenge for photocatalytic reactions is to find a stable semiconductor-based material capable of splitting water using a large fraction of sun light.