Schönig M, Frittmann S, Schuster R. Identification of electrochemically adsorbed species via electrochemical microcalorimetry: sulfate adsorption on Au(111).
Chemphyschem 2022;
23:e202200227. [PMID:
35510390 PMCID:
PMC9542382 DOI:
10.1002/cphc.202200227]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 04/28/2022] [Indexed: 11/11/2022]
Abstract
We investigate compositional changes of an electrochemical interface upon polarization with electrochemical microcalorimetry. From the heat exchanged at a Au(111) electrode upon sulfate adsorption, we determine the reaction entropy of the adsorption process for both neutral and acidic solutions, where the dominant species in solution changes from SO42− to HSO4−. In neutral solution, the reaction entropy is about 40 J mol−1 K−1 more positive than that in acidic solution over the complete sulfate adsorption region. This entropy offset is explicable by a deprotonation step of HSO4− preceding sulfate adsorption in acidic solution, which shows that the adsorbing species is SO4* in both solutions. The observed overall variation of the reaction entropy in the sulfate adsorption region of ca. 80 J mol−1 K−1 indicates significant sulfate‐coverage dependent entropic contributions to the Free Enthalpy of the surface system.
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