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Title: Surface structures and phase transitions at the Au(100)-Br interface: pH and CO effects

Abstract

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 ismore » 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.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Director. Office of Science. Office of Basic Energy Sciences. Materials Science and Engineering Division (US)
OSTI Identifier:
827965
Report Number(s):
LBNL-55918
R&D Project: 505601; 500901; TRN: US200426%%1026
DOE Contract Number:  
AC03-76SF00098
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 108; Journal Issue: 17; Other Information: Journal Publication Date: 04/29/2004; PBD: 29 Jul 2004
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ADSORPTION; ANIONS; BROMIDES; ELECTRODES; PROBES; REMOVAL; SCATTERING

Citation Formats

Blizanac, Berislav B, Lucas, Chris A, Gallagher, Mark E, Ross, Philip N, and Markovic, Nenad M. Surface structures and phase transitions at the Au(100)-Br interface: pH and CO effects. United States: N. p., 2004. Web. doi:10.1021/jp037623u.
Blizanac, Berislav B, Lucas, Chris A, Gallagher, Mark E, Ross, Philip N, & Markovic, Nenad M. Surface structures and phase transitions at the Au(100)-Br interface: pH and CO effects. United States. https://doi.org/10.1021/jp037623u
Blizanac, Berislav B, Lucas, Chris A, Gallagher, Mark E, Ross, Philip N, and Markovic, Nenad M. Thu . "Surface structures and phase transitions at the Au(100)-Br interface: pH and CO effects". United States. https://doi.org/10.1021/jp037623u.
@article{osti_827965,
title = {Surface structures and phase transitions at the Au(100)-Br interface: pH and CO effects},
author = {Blizanac, Berislav B and Lucas, Chris A and Gallagher, Mark E and Ross, Philip N and Markovic, Nenad M},
abstractNote = {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.},
doi = {10.1021/jp037623u},
url = {https://www.osti.gov/biblio/827965}, journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
number = 17,
volume = 108,
place = {United States},
year = {2004},
month = {7}
}