An STM investigation of formic acid adsorption on oxygen precovered Cu(110)

We have used STM to observe the development of overlayer structures upon adsorption of formic acid on O(0.5 ML):Cu(110) between 300 and 420 K. At 300 K c(2 x 2) and (3 x 1) formate structures are initially produced together with a c(6 x 2) oxygen structure indicating compression of the oxygen islands. Further formic acid adsorption results in the loss of these structures, leaving distinct small islands on a mostly featureless background. Annealing to 400 K regenerates the c(6 x 2) oxygen structure and well-ordered c(2 x 2) and (4 x 1) formate structures, the latter also being the dominant formate structure produced by formic acid adsorption between 350 and 420 K.