Industrial water electrolysis: Present and future

Present and developing technologies for the production of hydrogen from water are reviewed in the framework of the fundamental thermodynamic and kinetic constraints which govern the process. Attention is directed primarily to the direct electrolysis processes. Alkaline unipolar and bipolar, solid polymer electrolyte, and vapour-phase technologies are compared. It is concluded that alkaline electrolysis at temperatures below 150°C will be economically preferred over the next decade, while vapour-phase electrolysis is a development of significant but longer-term interest.