title: Direct STM elucidation of the effects of atomic-level structure on Pt(111) electrodes for dissolved CO oxidation.
abstract: We  sought to establish a new standard for  direct comparison of electrocatalytic activity with surface structure using in situ scanning tunneling microscopy (STM) by examining the electrooxidation of CO in a CO-saturated solution on Pt(111) electrodes with steps, with combined electrochemical measurements, in situ STM, and density functional theory (DFT). On pristine Pt(111) surfaces with initially disordered (111) steps, CO oxidation commences at least 0.5 V lower than that for the main oxidation peak at ca. 0.8-1.0 V vs the reversible hydrogen electrode in aqueous perchloric acid solution. As the potential was cycled between 0.07 and 0.95 V, the CO oxidation activity gradually decreased until only the main oxidation peak remained. In situ STM showed that the steps became perfectly straight. A plausible reason for the preference for (111) steps in the presence of CO is suggested by DFT calculations. In contrast, on a pristine Pt(111) surface with rather straight (100) steps, the low-potential CO oxidation activity was less than that for the pristine, uncycled (111) steps. As the potential was cycled, the activity also decreased greatly. Interestingly, after  cycling,  in situ STM showed that (111) microsteps were introduced at the (100) steps. Thus, potential cycling in the presence of dissolved CO highly favors  formation of (111) steps. The CO oxidation activity in the low-potential region decreased in the following order: disordered (111) steps > straight (100) steps > (100) steps with local (111) microsteps ≈ straight (111) steps.
authors.affiliation: Fuel Cell Nanomaterials Center, University of Yamanashi, Kofu, 400-0021, Japan. jinukai@yamanashi.ac.jp
authors.forename: Junji
authors.initials: J
authors.lastname: Inukai
authors.forename: Donald A
authors.initials: DA
authors.lastname: Tryk
authors.forename: Takahiro
authors.initials: T
authors.lastname: Abe
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Wakisaka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Uchida
authors.forename: Masahiro
authors.initials: M
authors.lastname: Watanabe
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry*; D004566:Electrodes; D016252:Microscopy, Scanning Tunneling; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010984:Platinum / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties
chemical_list: D010984:Platinum; D002248:Carbon Monoxide