Electrocatalytic reduction of nitrite on a polycrystalline rhodium electrode

The electrochemical reduction of HNO 2 / NO 2 - was studied on a rhodium electrode as a function of pH and potential ( E). N 2O is detected only in acidic media, while NH 3 formation occurs at low E independently of pH. This paper addresses the mechanism of the electrochemical reduction of HNO 2 and...

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Bibliographic Details
Published in:Journal of catalysis 2010-09, Vol.275 (1), p.61-69
Main Authors: Duca, M., van der Klugt, B., Hasnat, M.A., Machida, M., Koper, M.T.M.
Format: Article
Language:English
Subjects:
Catalysis
Chemistry
Crystallography
Electrochemistry
Electrodes
Exact sciences and technology
General and physical chemistry
Kinetics and mechanism of reactions
Nitrite
Nitrous acid
On-line mass spectrometry
Research methodology
Rhodium
Rotating-disk electrode
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
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Summary:The electrochemical reduction of HNO 2 / NO 2 - was studied on a rhodium electrode as a function of pH and potential ( E). N 2O is detected only in acidic media, while NH 3 formation occurs at low E independently of pH. This paper addresses the mechanism of the electrochemical reduction of HNO 2 and NO 2 - on polycrystalline rhodium. Intermediates and/or reaction products were detected by means of various (combined) techniques: rotating ring-disk voltammetry (for NH 2OH detection), online electrochemical mass spectrometry (for volatile products) and transfer experiments (for NO ads). In acidic media, HNO 2 depletion due to homogeneous-phase reactions generates dissolved NO: the latter species can be adsorbed at Rh and is reduced to N 2O when 0.3 < E < 0.5 V (vs. RHE), while HNO 2 is reduced in a diffusion-limited wave to mainly NH 3 at potentials preceding hydrogen evolution. In alkaline media, the predominant product for the reduction of NO 2 - when E < 0.2 V is still NH 3, which can poison the electrode via dehydrogenation to NH x ,ads species. For more positive potentials, reduction still occurs via NO ads and stops at NH 2OH for E > 0.3 V. The behavior of Rh is compared to Pt and explained in terms of general properties of these metals. A mechanistic scheme including NO, HNO 2 and NO 2 - is discussed.
ISSN:0021-9517
1090-2694
DOI:10.1016/j.jcat.2010.07.013