Alternating current measurements in scanning electrochemical microscopy, part 2: detection of adsorbates

Dao Trinh; Michel Keddam; Xosé Ramón Novoa; Vincent Vivier

doi:10.1002/cphc.201001085

Alternating current measurements in scanning electrochemical microscopy, part 2: detection of adsorbates

Chemphyschem. 2011 Aug 1;12(11):2177-83. doi: 10.1002/cphc.201001085. Epub 2011 May 31.

Authors

Dao Trinh¹, Michel Keddam, Xosé Ramón Novoa, Vincent Vivier

Affiliation

¹ LISE-UPR du CNRS, Université Pierre et Marie Curie, Paris, France.

PMID: 21630411
DOI: 10.1002/cphc.201001085

Abstract

A scanning electrochemical microscope (SECM) in ac mode is used for the characterisation of the adsorption process during the hydrogen evolution reaction (HER) in sulfuric acid solution. It is shown that this technique allows quantitative analysis of the adsorption process, and measurements of the differential capacitance with the frequency as parameter are obtained. The time constant for relaxation of adsorbed hydrogen (H(ads)) is approximately 2 Hz, and analysis of the Nyquist plot allows direct evaluation of the charge involved. In addition, the direct comparison of the usual electrochemical impedance data and ac-SECM results obtained simultaneously permits characterisation of processes occurring at the surface and in solution.