In situ infrared monitoring of hydrogen adsorption/desorption at a germanium electrode

Upon potential cycling in acidic electrolyte, the coverage of Ge electrodes can be changed from GeH to GeOH. In situ infrared spectroscopy reveals that hydrogen adsorbs and desorbs at Ge in mono- and dihydride configurations. Comparison of (111)- and (100)-oriented electrodes shows that the Ge surface is rough at the atomic scale and that this roughening takes place through (111) microfacetting. This facetting can account for the attenuated polarization dependence of the GeH absorption and its enhancement through local field effects. Finally, the band edge shifts which are observed upon hydrogen adsorption/desorption appear related to a change in the Ge surface charge rather than to a dipolar effect.