MEMBREL cell

It is state of the art to deposit the platinum catalyst on the membrane surface by a diffusion process in which platinum salt solutions (from the cathode side of the membrane) and a reductant, like hydrazine, are counter-diffusing causing reductive precipitation of dispersed platinum close to and on the surface of the membrane. The BBC Membrel cell is reported to contain a catalyst load of only 0.2 mg Pt per square centimeter (97). The cathode is reported to exhibit only from 50 to 70 mV overpotential at current densities of 1 A/cm2 and 80°C. 

Membrel cell — (membrane electrolysis) Electrochemical cell developed by BBC Brown Boveri Ltd, now joined with ASEA AB, to ABB Asea Brown Boveri Ltd) for water electrolysis. A polymeric cation exchange membrane acting as -> solid electrolyte is placed between a catalyst-coated porous graphite plate acting as cathode and a catalyst-coated porous titanium plate acting as anode. 

Fig. 5.14 The ABB-Membrel process for electrolytic generation of ozone using a solid polymer electrolyte, (a) Schematic of the Membrel cell, (b) A complete ozone treatment unit including a circulating system, UV lamps, control panel and power supply. The system is used to deliver up to 2 m h ultrapure water to a pharmaceutical production plant. Ozone is produced by a single Membrel cell of 30 cm active electrode area. The cell is shown by an arrow. (Photographs courtesy Asea Brown Boveri Ltd.)...

Electrolysis of water contained within a perfluorinated sulphonic acid membrane (Membrel water electrolysis) developed by ABB [133,201-205] and Sasakura [200]. Current efficiencies reach 14-15% at current densities of 10000 A m2 and more. The cells are generally immersed directly in the water so that ozone is introduced directly into the water to be treated, Fig. 18. 

Asea Brown Boveri of Switzerland has commercialized the MEMBREL process for the electrolytic generation of ozone. The synthesis takes place in a cell whose anodic section is made of titanium and the cathodic section of stainless steel. A Nafion membrane (Du Pont) acts not only as the electrolyte for the system, but also as the separator. This membrane is sandwiched between the anode (lead dioxide) and the cathode (platinum). Electrolysis takes place at a total cell voltage of 3-5 V with a current density of 0.5 - 2.0 A/cml The corresponding cathodic reaction is hydrogen evolution. 

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