Assisted deprotonation of formic acid on Cu(111) and self-assembly of 1D chains.

Formic acid (HCOOH) deprotonates on the open surfaces of Cu(110) and Cu(100) when exposed at 300 K. However, this does not occur on the close-packed surface of clean Cu(111). In this study, we show that the deprotonation of formic acid on atomically flat Cu(111) surfaces can be induced by pre-adsorbing polymeric formic acid clusters at low temperatures, and then annealing the system to break the acidic O-H bond of HCOOH adsorbed on the edges of the polymeric clusters. The thermal activation of HCOOH to bidentate formate was studied using a combination of infrared reflection absorption spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, and near edge X-ray absorption fine structure spectroscopy. Extended 1D formate structures self-assemble due to a templating effect introduced by the formation of long α-polymeric formic acid chains commensurate with the substrate.