The Model of Bockris and Uosaki

In the early stages of study of photoelectrochemical kinetics, two extreme models were presented. One is the model of Bockris and Uosaki, in which the charge transfer step was considered to be the rate-determining step and the other is Butler s model, in which the semiconductor/ele rolyte interface was considered as a Schottky barrier, i.e., the electrochemical kinetics were neglected and all the potential drop occurred only within the semiconductor. 

In this section, these two models are explained first, then the effects of other terms will be considered. 

Bockris and Uosaki calculated photocurrent-potential relations mainly for the hydrogen evolution reaction (HER) at p-type semiconductors with the assumption that the following is the ratedetermining step  

x o gives the number of electrons arriving at the surface per unit area per unit time which are excited between x and x + dx. Therefore, the total number of electrons arriving at the surface per unit 

They also took into account the band edge movement due to applied external potential, and their final expression for the photocurrent, ip, is given by 

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