Explosive evolution of hydrogen abstraction of water on oxidized Ag(110) surfaces studied by scanning tunnelling microscopy

Abstract

Scanning tunnelling microscopy was used for studying surface structural evolution in the course of the hydrogen abstraction of H₂O by O adatoms on oxidized Ag(110) surfaces where quasi-1D AgO chains form ordered structures. The reaction initially takes place slowly on Ag(110)–(5 × 1)O at the end of the AgO chain, whereas the reaction accelerates explosively upon the appearance of a reaction front that propagates along the direction perpendicular to the chain. The surface morphology of the region swept over by the reaction front completely changes from a (5 × 1)-O to a (2 × 3) structure with many rectangular islands possibly due to the formation of H₂O(OH)₂. The induction time and explosive acceleration with the propagating reaction front imply that the reaction proceeds autocatalytically. The water clusters hydrating OH adsorbates play likely a central role in accelerating the reaction by supplying H₂O to the O adatoms in the AgO chains at the reaction front.