Poison Tolerant Platinum Catalysed Cathodes for Membrane Cells

Abstract

Chlorine and sodium hydroxide are manufactured almost/exclusively by the electrolysis of brine (aqueous sodium chloride), the overall reaction being represented by eqn (1):

$$ 2NaCl + H_2 O \to 2NaOH + Cl_2 \uparrow + H_2 \uparrow $$

(1)

During the past decades, the chlor-alkali industry has been revolutionised by the advent of anodes catalysed by precious metal, which have almost entirely superseded the graphite previously used. Increasing public concern for environmental pollution has also led to pressure for a change from mercury cathodes, and from asbestos as diaphragm separators. This is encouraging a move towards cells incorporating ion exchange membrane separators, enabling greater efficiency in manufacturing, and making products of higher purity.