A NEW LOW HYDROGEN OVERVOLTAGE CATHODE FOR CHLORALKALI ELECTROLYSIS CELL

A new low hydrogen overvoltage cathode has been developed by using a composite-coating method. In the coating process, Raney nickel alloy and a hydrogen absorbing alloy are uniformly dispersed in a modified Watts type bath and electroplated on to a cathode substrate. During the plating, pulverized Raney nickel alloy and the hydrogen absorbing alloy are co-deposited on the substrate with nickel ions. The deposited nickel forms a nickel matrix and strongly adheres the Raney nickel alloy and the hydrogen absorbing alloy. The microscopic structure of the coating is dendritic, that enables the co-deposited Raney nickel alloy particles and the hydrogen absorbing alloy particles to expose to the surface effectively. The cathode shows a low hydrogen overvoltage (ca. 90 m V at 90 degrees C, at 30 A dm(-2) in a 35 wt.% NaOH) and has excellent stability under cell short-circuiting shutdown as well as under normal operating condition. The performances and the stability mechanism under shutdown conditions are discussed.