Advanced alkaline water electrolysis using inorganic membrane electrolyte (I.M.E.) technology

The Belgian Hydrogen Research Programme, aiming at the development of a new concept in advanced alkaline water electrolysis has resulted in demonstration projects with prototype electrolyser units. The new concept, named I.M.E. technology (inorganic membrane electrolyte) produces hydrogen under pressure (0.5-4.0 MPa) at current densities up to 12500 Am^-2 and temperatures not exceeding 120°C. Electrocatalysts based on non-noble metals are deposited on perforated nickel plates. These electrodes are pressed against an inorganic ion-exchanger membrane based on polyantimonic acid. Circular cells (surface area up to 0.2 m²) are assembled in a filter-press type manner. Prototype electrolysers, having hydrogen production rate from 2.5 Nm³h^-1 to 25 Nm³h^-1 have been constructed and tested. Multicell performances (up to 60 unit cells) at 2000 Am^-2 are 1.6 V at 90°C and even 1.5 V at 120°C. At a 5 times higher current density (10000 Am^-2) cell voltages only increase with 0.3 V at 90°C and 0.2 V at 120°C. Since 100% Coulombic efficiency has been measured in these 60 unit cell stacks the electrical power consumption (at 2000 Am^-2) per normal cubic meter of hydrogen produced is 3.81 kWh at 90°C and 3.65 kWh at 120°C. A techno-economic analysis was performed to quantify the cost of hydrogen as a function of design parameters such as module cost and module performance capability.