A survey of five year intensive R&D work in Belgium on advanced alkaline water electrolysis

A Belgian hydrogen research programme, aimed at the development of a new concept in advanced alkaline water electrolysis, has been carried out at the Nuclear Research Centre (S.C.K./C.E.N.) Mol, under the auspices of the Commission of the European Communities. An inorganic ion-exchanger membrane, based on polyantimonic acid, has up to now shown its chemical stability for up to 10,000 hours in alkaline solutions at 120°C, and its ion conducting and gas separating properties under electrolysis for 5000 hours. Electrocatalysts based on non-noble metals, deposited onto a perforated nickel plate, have been investigated. Nickel sulphide at the cathode and spinel oxides based on nickel and/or cobalt at the anode were investigated. Multicells (1-5 kW) were assembled using the so called Inorganic-Membrane-Electrolyte (I.M.E.) Technology. Hydrogen is produced under pressure (0.3-0.5 MPa) and performances are measured at current densities up to 10 kAm^-2 and temperatures up to 120° in 15 wt% NaOH. Cell voltages of 1.6 V at 90°C and 1.5 V at 120°C are obtained at 2 kAm^-2. Due to the flat characteristic of the cell voltage-current density relationship, only a 0.2 V increase in cell voltage is observed when increasing the current density by a factor of 5 (from 2 kAm^-2 to 10 kAm^-5). Electrolyte concentrations could be lowered by a factor of two (from 30 wt% to 15 wt%) without any losses in cell performances, due to the intrinsic properties of the polyantimonic-acid based membrane. As a result of the successful laboratory research, a prototype electrolyser unit which produces 25 Nm³ hydrogen per hour under 0.5 MPa pressure is under construction within the association Cobelcon (Consortium of Belgian Industries + S.C.K./C.E.N.).