The interplay between hydrogen evolution reaction and nitrate reduction on boron-doped diamond in aqueous solution: The effect of alkali cations

The nitrate ion reduction was studied on boron-doped diamond (BDD) electrodes by real-time on-line differential electrochemical mass spectrometry (DEMS) coupled with chronoamperometry in K⁺, Na⁺ cation-containing electrolyte solutions. It was found, via steady state voltammetry, that the hydrogen evolution reaction (HER) was affected by the presence of K⁺ or Na⁺. A moderate HER occurs in K ⁺-containing electrolyte solution favoring the reaction between NO₃^- and H₂ species, whereas in Na ⁺-containing electrolyte solutions, the HER kinetics was more important leading to a suppression of molecular nitrogen generation. The use of isotope-labeled nitrogen and DEMS confirmed the influence of alkali cations toward the nitrate ion reduction.