Analysis of the Hydrogen Formation at GaAs Electrodes by Impedance Spectroscopy Investigations

The kinetics of the hydrogen formation from protons as well as from water has been studied over a large potential range by measuring the interfacial current and the impedance spectrum in dependence of the electrode potential simultaneously. According to a quantitative analysis of the experimental data a semilogarithmic plot of the current j versus the potential across the space charge region ϕsc yielded a straight line of an ideal slope of 60 mV/decade. In addition it was found that the j‐ϕsc behavior at n‐GaAs electrodes can be described by the thermionic emission model, i.e., the electron transfer rate is controlled by the electron transport across the space charge region. From this result it has been concluded that the reduction of protons is an extremely fast process. The mechanism and the consequences of this surprising result are discussed in detail.