On the mechanism and energetics of electrochemical alloy formation between mercury and platinum for mercury removal from aqueous solutions
Journal article, 2024

Mercury pollution is an acute global concern threatening the health of humans and wildlife. Thus, there is a need for new and improved techniques to reduce emissions and remove toxic mercury from aqueous environments. Electrochemical alloy formation, specifically between mercury ions in aqueous solution and a platinum electrode, emerges as a promising solution. Through analysis of reaction mechanisms and energetics related to the formation and dissolution of the PtHg4 alloy, this study aims to deepen our understanding of the underlying processes of effective electrochemical mercury removal. Potentiodynamic measurements indicate rapid alloy formation at a clean platinum surface, proceeding with only trace amounts of metallic mercury on the surface. However, once the electrode surface has sufficient mercury coverage with an alloy thickness of around 1.5 nm, clear evidence of metallic mercury on the surface is observed. Furthermore, the amount of absorbed mercury on the cathode increases linearly in time. The onset potential for the alloy formation is experimentally determined using electrochemical quartz crystal microbalance with dissipation monitoring to be approximately 0.64 V vs. SHE, and the alloy dissolution (oxidation) onset potential is found to be approximately 0.98 V vs. SHE, at a mercury ion concentration of 10 mg/L. Density functional theory calculations are used to provide a theoretical value for the reversible potential from a thermodynamics perspective, yielding a value of 0.78 V vs. SHE at a mercury ion concentration of 10 mg/L. This value is in excellent agreement with the experimental results, suggesting an overpotential of about 0.14 and 0.20 V for the alloy formation and oxidation, respectively. These findings provide important information on the reaction mechanisms and overpotentials of the PtHg4 alloy formation and dissolution, which are key factors for development of large-scale mercury removal based on this technique, as well as fundamental understanding of the electrochemical alloy formation between mercury ions and platinum.

Mercury removal

EQCM

Platinum

DFT

Electrochemical alloy

Author

Vera Roth

Chalmers, Physics, Chemical Physics

Mikael Valter

Chalmers, Physics, Chemical Physics

Linnéa Strandberg

Chalmers, Physics, Chemical Physics

Mohammad Reza Bilesan

Lappeenranta-Lahti University of Technology (LUT)

Julia Järlebark

Applied Chemistry

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Jan Jamroz

Warsaw University of Technology

Chalmers, Physics, Materials Physics

Björn Wickman

Chalmers, Physics, Chemical Physics

Electrochimica Acta

0013-4686 (ISSN)

Vol. 507 145137

Subject Categories

Inorganic Chemistry

Materials Chemistry

Environmental Sciences

DOI

10.1016/j.electacta.2024.145137

More information

Latest update

10/15/2024