Electric field–prevented adsorption of hydrogen on supported gold nanoparticles

The adsorption of hydrogen on the surface of gold nanoparticles deposited on a graphite support was studied in the presence of an external electric field by means of scanning tunneling microscopy (STM) and spectroscopy (STS). Hydrogen was adsorbed from the gas phase onto the surface of gold nanoparticles synthesized by impregnation-precipitation method. During the adsorption process, the STM tip was removed from the surface of the sample so that the measurable tunneling current could not flow, and potential differences of various polarities were applied to the vacuum gap between the sample and the grounded tip. Thus, the system of the STM tip and sample surface formed an asymmetric capacitor inside which an inhomogeneous electric field existed. No hydrogen adsorption was observed in the case of a positive potential difference, while dissociative adsorption of hydrogen took place in the cases of zero and negative potential differences. The ability to control the adsorption process of hydrogen by means of a weak electric field was demonstrated.