Field ion microscopy combined with video techniques and chemical probing reveals the existence of catalytic oscillatory patterns at the nanoscale. This is the case when a rhodium nanosized crystal—conditioned as a field emitter tip—is exposed to hydrogen and oxygen. Here, we show that these nonequilibrium oscillatory patterns find their origin in the different catalytic properties of all of the nanofacets that are simultaneously exposed at the tip's surface. These results suggest that the underlying surface anisotropy, rather than a standard reaction–diffusion mechanism, plays a major role in determining the self-organizational behavior of multifaceted nanostructured surfaces. Surprisingly, this nanoreactor, composed of the tip crystal and a constant molecular flow of reactants, is large enough for the emergence of regular oscillations from the molecular fluctuations.

We have studied oxygen interaction with Au crystals (field emitter tips) using time-resolved (atom-probe) field desorption mass spectrometry. The results demonstrate no adsorption to take place on clean Au facets under chosen conditions of pressures $(p<{10}^{-4}\mathrm{mbar})$ and temperatures $(T=300–350\mathrm{K})$ . Steady electric fields of $6\mathrm{V}∕\mathrm{nm}$ do not allow dissociating the oxygen molecule. The measured ${\mathrm{O}}_2^{+}$ intensities rather reflect ionization of ${\mathrm{O}}_2$ molecules at critical distances above the Au tip surface. Certain amounts of $\mathrm{Au}–{\mathrm{O}}_2$ complex ions can be found at the onset of Au field evaporation. Calculations by density functional theory (DFT) show weak oxygen end-on interaction with ${\mathrm{Au}}_{10}$ clusters $(\Delta E=0.023\mathrm{eV})$ and comparatively stronger interaction with ${\mathrm{Au}}_1∕\mathrm{Au}\left(100\right)$ model surfaces $(\Delta E=0.25\mathrm{eV})$ . No binding is found on {210} facets. Including (positive) electric fields in the DFT calculations leads to an increase of the activation energy for oxygen dissociation thus providing an explanation for the absence of atomic oxygen ions from the field desorption mass spectra.