Abstract

This work deals with the interconversions of various nitrogen-containing compounds on Pt(111) and Pt(100) electrodes in contact with acidic solutions of nitrate. Via its reduction, nitrate acts merely as the source of adsorbed nitrogen-containing intermediates, which then undergo complex oxidative or reductive transformations depending on the electrode potential. Nitrate reduction to ammonium is structure sensitive on Pt(111) and Pt(100) because it is mediated by *NO, the adsorption and reactivity of which is also structure sensitive. Accordingly, previous knowledge from *NO electrochemistry is useful to streamline nitrate reduction and elaborate a comprehensive picture of nitrogen-cycle electrocatalysis. Our overall conclusion for nitrate reduction is that the complete conversion to ammonium under prolonged electrolysis is possible only if the reduction of nitrate to nitric oxide, and the reduction of nitric oxide to ammonium are feasible at the applied potential. Among the two surfaces studied here, this condition is fulfilled by Pt(111) in a narrow potential region.

Highlights

  • Electrochemical reactions involving nitrogen-containing compounds have been traditionally attractive to understand fundamentals of electrochemical surface science and electrode kinetics [1e3]

  • When scanning from þ0.07 VRHE in the positive direction, nitrate reduction starts above þ0.25 VRHE

  • The reductive current is maximized at þ0.35 VRHE and decreases, probably because intermediates of nitrate reduction remain adsorbed and are not further reduced

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Summary

Introduction

Electrochemical reactions involving nitrogen-containing compounds have been traditionally attractive to understand fundamentals of electrochemical surface science and electrode kinetics [1e3]. Such reactions include (but are not limited to) nitrate reduction, nitric oxide reduction and oxidation [4,5], nitrous oxide reduction [6,7] or ammonia oxidation [8,9]. The reactions of nitrogen-containing compounds are complicated, as they typically involve several bond-breaking or bong-forming events and several intermediates and final products are formed. These processes are interconnected within the biogeochemical nitrogen cycle and often share the same intermediates [16]. Platinum single-crystal electrodes have been utilized to understand structural effects on the reactivity and product distribution [2,31e34]

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