Understanding the effect of electric fields on the local reactivity of catalyst surfaces is of interest to heterogeneous catalysis, primarily for electrochemistry. Using Scanning Tunneling Microscopy experiments, we show how the concentration and spatial distribution of hydrogen atoms on Pd(111) can be controllably manipulated with nanometer resolution, by the application of local electric fields. First-Principles DFT calculations explain the phenomena on the basis of field-dependent changes in the adsorption energy of H in both surface and subsurface layers. We show that the binding energy changes can be rationalized based on the interplay of changes in the dipole moment and adsorbate polarizability on the Pd(111) surface in the presence of external electric fields. The ability to locally modify the surface concentration of adsorbates opens the possibility of patterning surface reactivity on a nanometer scale.

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