The role of surface deconstruction in the autocatalytic decomposition of formate and acetate on Ni(110)

The adsorption of formate and acetate on the Ni(110) surface has been investigated with STM, LEED, TPRS, and XPS. At saturation coverage formate and acetate form a c(2 x 2) structure amid a pitted surface, which is suggestive of the incorporation of "added" Ni atoms into the c(2 x 2) structure. Heating the surface to 350 K to decompose the formate produces islands of step height, indicative of the release of Ni from the c(2 x 2) structure during HCOO decomposition. Upon further heating to 370 K the islands dissipate and p(4 x 1)-CO domains appear. Heating the acetate-covered surface affects a restructuring of the c(2 x 2) to scattered domains of a p(8 x 1) structure, which is attributed to acetate. Concomitant with this restructuring is the release of Ni to form islands of step height. Upon further heating the acetate decomposes to yield a p(4 x 5)-C covered surface. The present investigation adds further insight into the phenomena underlying the autocatalytic decomposition of formate and acetate. It is suggested that the added Ni in the formate structure facilitates the decomposition of formate into CO2, H-2, and scattered Ni-x nuclei, which act as sites for further formate decomposition.