Tracking oxygen atoms in electrochemical CO oxidation – Part I: Oxygen exchange via <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"><mml:msub><mml:mtext>CO</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:math> hydration

We report a new method to measure the kinetic rate constant of CO2 hydration using electrochemical oxidation carbon monoxide (CO oxidation) in isotope-labeled electrolyte. CO is often used as model reaction investigate surface metallic electrocatalysts, most notably stripping experiments. Using chip-based electrochemistry mass spectrometry with 18O-labeled electrolyte we show that: 1) For experiments on Pt, one oxygen product comes from reactant and other electrolyte, consistent Langmuir-Hinshelwood mechanism involving adsorbates *CO *OH. 2) Some formed subsequently exchanges via short-lived carbonic acid. use time-dependent isotopic ratios calculate compare it literature. By doing this at two different temperatures that robust provide an accurate measurement for hydration. Chip-based combined labeling thus shown be versatile powerful tool elucidating mechanistic aspects homogeneous reactions well electrocatalytic reactions.