Electrochemical reduction of nitrate to ammonia at modified gold electrodes
2004; Elsevier BV; Volume: 49; Issue: 9-10 Linguagem: Inglês
10.1016/j.electacta.2003.11.025
ISSN1873-3859
Autores Tópico(s)Catalytic Processes in Materials Science
ResumoThe electrocatalytic activity of Au electrodes modified with thiourea (TU), urea (U), iodide ions (I−) and sulfide ions (S2−) towards reduction of NO3− to NH3 have been tested. Cyclic voltammetry (CV) of the TU/Au electrode in 0.5 M NaNO3 (N2-saturated, pH 12.5) revealed an increase of the reduction peak of NO3− at ca. +0.75 V versus reversible hydrogen electrode (RHE) more than at the bare (i.e., unmodified) Au electrode. On the other hand, the intensity of this peak is more depressed at I−/Au, S2−/Au and U/Au electrodes. The Tafel slope is almost the same for the two reactions, i.e., the hydrogen evolution reaction (HER) and the nitrate reduction reaction suggesting a common rate-determining step (r.d.s.) for both reactions. Galvanostatic electrolysis of the basic nitrate solution resulted in three major reduction products i.e., NH3, NO2− and H2. The TU/Au electrode showed the highest current efficiency, Q, of the NH3 production (about 85%), which is about 6.5 times higher than that of the NO2− production. While the I−/Au and S2−/Au showed a sharp increase in the current efficiency for the hydrogen evolution reaction to about 43 and 47%, respectively, with a concurrent depression of the total current efficiency of the nitrate reduction.
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