Behaviour of and mass transfer at gas-evolving electrodes

A completes set of models for the mass transfer of indicator ions to gas-evolving electrodes with different behaviour of bubbles is described theoretically. Sliding bubbles, rising detached single bubbles, jumping detached coalescence bubbles and ensembles of these types of bubbles are taken into consideration as well as the behaviour of various types of bubbles, in particular, the detached coalescence bubble is discussed. The set of model is checked using literature data of mass-transfer coefficients for ferricyanide ions and ferrocyanide ions to, respectively, a hydrogen-evolving and an oxygen-evolving electrode in alkaline solutions under conditions of forced convection of solution. It has been found that the mass transfer of indicator ions to various types of gas-evolving electrodes can be described well by the set of models proposed.