Formic acid oxidation on Pt deposit model catalysts on Au: Single-layered Pt deposits, plateau-type Pt deposits, and conical Pt deposits

This work presents the formic acid oxidation (FAO) behavior on three model Pt deposit catalysts on Au. The investigated model Pt catalysts were single-layered Pt deposits, plateau-type Pt deposits and tall conical Pt deposits, produced via irreversible adsorption of Pt ions according to the protocols of conventional route, CO route and iodine route, respectively. The shapes and populations of the model Pt deposits were controlled by the deposition protocols and number of deposition cycles. The most effective Pt deposit catalyst in FAO was verified to be single-layered one with a population of ∼50% which inhibited dehydration (poison formation) and promoted dehydrogenation. As the population of Pt deposits became higher than 50%, the dehydration process activated to decrease the FAO catalytic efficiency. Furthermore, multiple layered Pt deposits such as conical ones were not so efficient due to activation of dehydration even at a population below 50%. More detailed analysis of the observed voltammograms in the negative-going scan suggested that dehydrogenation took place at two different potentials depending on the shapes and populations of Pt deposits. One was low potential dehydrogenation occurring on separated single-layered Pt deposits at 0.14 V; the other was high potential dehydrogenation taking place on continuous Pt surface at 0.34 V. This particular suggestion was successfully applicable to explaining the FAO voltammograms of Pt electrodes of disk and nanoparticle.