Surface X-ray Scattering of Stepped Surfaces of Platinum in an Electrochemical Environment: Pt(331) = 3(111)-(111) and Pt(511) = 3(100)-(111)

Abstract

Real surface structures of the high-index planes of Pt with three atomic rows of terraces (Pt(331) = 3(111)-(111) and Pt(511) = 3(100)-(111)) have been determined in 0.1 M HClO(4) at 0.1 and 0.5 V(RHE) with the use of surface X-ray scattering (SXS). The surfaces with two atomic rows of terraces, Pt(110) = 2(111)-(111) and Pt(311) = 2(100)-(111) = 2(111)-(100), are reconstructed to a (1 × 2) structure according to previous studies. However, the surfaces with three atomic rows of terraces have pseudo-(1 × 1) structures. The interlayer spacing between the first and the second layers, d(12), is expanded 13% on Pt(331) compared to that of the bulk, whereas it is contracted 37% on Pt(511). The surface structures do not depend on the applied potential on either surface.

Surface X-ray Scattering of Pd(110) and Pd(311) in Electrochemical Environments

“…Surface energy of the close-packed (111) structure is lower compared with other surfaces; enlargement of the (111) terrace width stabilizes the surface structure after the reconstruction to (1 © 2). 24 On the surfaces with more than 3 atomic rows of terrace, however, (111) terrace width does not increase after the (1 © 2) reconstruction. Thus enlargement of (111) terrace width is regarded as a motive force to the (1 © 2) reconstruction on single crystal electrodes of Pt.…”

“…22 However, the surfaces composed of 3 atomic rows of terrace, such as Pt(310) = 3(100)-(110), 23 Pt(511) = 3(100)-(111) and Pt(331) = 3(111)-(111), have unreconstructed (1 © 1) structures. 24 Reconstruction to (1 © 2) enlarges (111) terrace width on the surfaces with 2 atomic rows of terrace such as Pt(110) and Pt(311). Surface energy of the close-packed (111) structure is lower compared with other surfaces; enlargement of the (111) terrace width stabilizes the surface structure after the reconstruction to (1 © 2).…”

“…Thus enlargement of (111) terrace width is regarded as a motive force to the (1 © 2) reconstruction on single crystal electrodes of Pt. 24 The ORR activity was discussed on the basis of the surface structure determined with SXS, and the active site for the ORR is assigned to (111) terrace edge on Pt electrodes. 9 There have been few reports on the real surface structures of single crystal electrodes of Pd in electrochemical environments.…”

Elucidation of Activity Enhancement Factors for the Oxygen Reduction Reaction on Platinum and Palladium Single Crystal Electrodes

“…Real surface structures of the high index planes of Pt were also determined using SXD in 0.1 M HClO 4 . [28][29][30] Surfaces composed of two atomic rows of terrace such as Pt(110) and Pt(311) are reconstructed to (1 © 2) structure, whereas surfaces with more than three atomic rows of terraces have unreconstructed (1 © 1) structure. 30 Interlayer spacing between the first and the second layers d 12 is expands 13% compared with the bulk on Pt(331) that is composed of 3 atomic rows of (111) terrace and monatomic height (111) step, whereas d 12 is contracted 37% on Pt(511) that consist of 3 atomic rows of (100) terrace and monatomic height of (111) step.…”

“…30 Interlayer spacing between the first and the second layers d 12 is expands 13% compared with the bulk on Pt(331) that is composed of 3 atomic rows of (111) terrace and monatomic height (111) step, whereas d 12 is contracted 37% on Pt(511) that consist of 3 atomic rows of (100) terrace and monatomic height of (111) step. 30 STM study showed that bare Pd(111) has unreconstructed (1 © 1) structure in electrochemical environments. 31 Structures of adsorbed iodine were determined on Pd(111), Pd(100) and Pd(110) in 0.05 M H 2 SO 4 using STM, 32 however, real surface structures of bare Pd(100) and Pd(110) were not known in electrochemical environments.…”