Surface structures and phase transitions at the Au(100)-Br interface: pH and CO effects
- LBNL Library
The surface reconstruction of Au(100) and the formation of an ordered commensurate c(sqrt 2 x 22 sqrt 2)R45o adlayer of Br (Brad) have been studied by a combination of electrochemical (EC) and surface X-ray scattering (SXS) measurements. Emphasis is placed on linking the microscopic structural information concerning the Brad adlayer to the voltammetric and other macroscopic electrochemical responses, including using the rotating ring disk electrode (RRDE) measurements for determining the surface coverage by Brad. It is found that the potential-induced hexagonal (''hex'') to (1 x 1) transition of the Au surface coincides with Br- adsorption and occurs faster in solutions containing Br- anions than in Br--free solutions. In agreement with previous SXS results, in acid solutions, Brad forms a c(sqrt 2 x sqrt 2)R45o structure at around 0.15 V. However, no ordered structures of Brad are observed in alkaline solution, although the cyclic voltammetry indicates that the order structure should be present at 0.12 V. Absence of an ordered Brad adlayer in alkaline solution is attributed to competitive adsorption between Brad and OHad. To probe the role of OHad on the ordering of the bromide adlayer, coadsorbed OHad is consumed in an electrochemical reaction in which strongly adsorbed OHad is removed from the surface by a relatively weakly adsorbed reactant, viz. COad. Under such experimental conditions, we found that (i) in acid solution the c(sqrt 2 x 2 sqrt 2)R45o structure develops/disappears more rapidly than in CO-free solution and (ii) in alkaline solution the c(sqrt 2 x 2 sqrt 2)R45o structure is formed in exactly the same potential region as in acid solution. We propose that the continuous removal of OHad in the Langmuir-Hinshelwood reaction (COad + OHad) CO2 + H+ + e- may stabilize the c(sqrt 2 x 2 sqrt 2)R45o structure in both acid as well as alkaline media.
- Research Organization:
- Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Basic Energy Sciences. Materials Science and Engineering Division (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 827965
- Report Number(s):
- LBNL--55918
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 17 Vol. 108
- Country of Publication:
- United States
- Language:
- English
Similar Records
Oxygen Reduction Reaction on Pt(111): Effects of Bromide
Structure of active phases during the course of electrocatalytic reactions