Well-defined inhomogeneous a-Sb2O4/VSbO4 catalysts were prepared using an electron lithography method to investigate the effects of µm order structures on an atomic scale catalytic reaction. X-ray photoelectron spectroscopy (XPS) and laser microscopy revealed that µm order structures were successfully developed on a Si substrate where an a-Sb2O4 micro line with a controlled width was deposited on VSbO4. We carried out a propene partial oxidation reaction on this surface and found that the acrolein formation rate was significantly influenced by the width and interval of the a-Sb2O4 µm line. The results of this study indicate the possibility of controlling the surface reaction by the inhomogeneity of the surface structure in the µm order.
In order to understand relation between surface structure and catalytic activity, we studied the Ni2P (1010) surface using scanning tunneling microscopy (STM). Atomic scale STM images of c(2×4) structure and (1×1) structure were obtained after annealing the sample at 653 K (denoted as surface structure I). The area of c (2×4) structure was decreased by the NO exposure at 573 K. A c(2×4) structure together with c(2×2) structure was obtained after the repeated sputtering-annealing treatments and reactions, which was called as surface structure II. Contrary to the surface structure I, this surface didnʼt change its structure by the NO exposure at 573 K. Since the (1×1) structure on the surface structure I had exposed Nit (tetrahedral Ni) and Nisp (square pyramid Ni) pairs, NO might be activated and destroy the c(2×4)structure, while c(2×2) structure on the surface structure II had no exposed Nit and Nisp pair so that surface structure II was less reactive. The removal of the surface P atoms is important for the activation of the Ni2P surface.
Electrochemical deposition of Ag on a 23× 3 reconstructed surface of Au(111) electrode at various potentials was followed by scanning tunneling microscope (STM) in situ in real time. Ag was nucleated on the faulted hcp region of the reconstruction and grew preferentially along the hcp lines (the 〈112〉 directions), resulted in a line shape. Formation of the Ag lines with biatomic height was more favored than that with monatomic height at more negative potentials in the range of −0.2∼+0.3 V (vs. Ag/AgCl). The growth mode of the potentiostatic electrochemical deposition of Ag on the reconstructed Au (111) electrode surface observed here is quite different from those previously reported for the electrochemical deposition on Au(111)-(1×1) electrode and deposition under ultra-high vacuum (UHV) condition on the reconstructed Au(111) surface, showing the importance both of substrate surface structure and electrode potential.
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