Towards Direct Electroanalysis in Seawater: Understanding the Role of the Buffer Capacity of Seawater in Proton-Coupled Electron Transfer Reactions

• Main Authors: Rachel L. Pindar (11845862), Christopher Batchelor-McAuley (1417645), Minjun Yang (120481), Richard G. Compton (1417648)
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 2021
• Subjects: Biophysics; Biochemistry; Microbiology; Inorganic Chemistry; Environmental Sciences not elsewhere classified; Biological Sciences not elsewhere classified; Chemical Sciences not elsewhere classified; towards direct electroanalysis; simple nernstian model; similar response measured; numerical simulations based; display excellent agreement; chemically reversible voltammetry; associated coupled chemistry; voltammetric timescale leads; high buffer concentrations; seawater requires understanding; leads either; concentrations approximately; thermodynamic parameters; split wave; platinum macroelectrodes; oxidation potential; literature values; electrochemical reactions; dissolved h; cathodic shift; carbonic acid; buffer capacity; authentic seawater; aqueous 0; 2 less; Carbonic acid
• Online Access: https://doi.org/10.1021/acs.jpcc.1c09142.s001

The study of electrochemical reactions in seawater requires understanding of the associated coupled chemistry with the components of seawater, especially the role of the carbonate–bicarbonate buffer system in the case of proton-coupled electron transfer reactions. We report the comparative paradigmatic voltammetric response of the reversible hydrogen oxidation reaction in the absence or presence of dibasic phosphate, formate, or bicarbonate. Electrochemically and chemically reversible voltammetry is seen in aqueous 0.7 M NaCl at platinum macroelectrodes in the absence of a buffer, while the presence of chemically stable buffer systems, such as phosphate or formate, leads either to a cathodic shift in the oxidation potential for high buffer concentrations or to a split wave for concentrations approximately a factor of 2 less than the dissolved H 2 . In the case of bicarbonate buffer, the dehydration of carbonic acid on the voltammetric timescale leads to chemically irreversible voltammetric behavior, with a similar response measured in authentic seawater. Numerical simulations based on a simple Nernstian model with literature values for kinetic and thermodynamic parameters are reported, which display excellent agreement with the experiment.