STMによるNi₂P(10-10)単結晶表面のNOとの反応性評価

抄録

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 didn't change its structure by the NO exposure at 573 K. Since the (1×1) structure on the surface structure I had exposed Ni_t (tetrahedral Ni) and Ni_sp (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 Ni_t and Ni_sp 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.