Effect of boron concentration on the electrochemical reduction of nitrateson polycrystalline diamond electrodes

The Raman spectra and voltammograms in 0.1M KCI, 0.1M KNO3 and 0.1M KCl + 0 .1 M KNO3 solutions of polycrystalline diamond electrodes vary systematical ly versus their boron content in the gas phase (200 to 14 000 ppm). Both ex hibit the same threshold (2000 ppm, about 1.2 x 10(20) B cm(-3)) correspond ing to the appearance of a low-wavenumber continuum in Raman spectra and to a factor of 10(3) jump in the electrochemical current. In 0.1 M KNO3 solut ion, the reduction of nitrates from -0.6 to about -2V cathodic potential oc curs with low hydrogen reduction. The correlation between the electronic an d electrochemical properties of these electrodes is discussed. (C) 2000 Els evier Science S.A. All Rights reserved.