Electrocatalytic reduction of nitrate at low concentration on coinage and transition-metal electrodes in acid solutions
Electrocatalytic reduction of nitrate at low concentration on coinage and transition-metal electrodes in acid solutions
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DOI：
10.1016/s0022-0728(02)01443-2
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发表时间：
2003-09-15
影响因子：
4.5
通讯作者：
Koper, MTM
中科院分区：
文献类型：
--
作者：
Dima, GE;de Vooys, ACA;Koper, MTM
使用循环伏安法 (CV)、计时电流法和微分电化学质谱 (DEMS) 进行比较研究，以确定酸性溶液中八种不同多晶电极（铂、钯、铑、钌、铱、铜、银和金）上 0.1 M 硝酸根离子的反应性。循环伏安法表明硝酸盐还原的电流密度很大程度上取决于电极的性质。对于过渡金属电极，活性按 Rh > Ru > Ir > Pd 和 Pt 的顺序降低；对于造币金属，活性按 Cu > Ag > Au 的顺序降低。 Ru、Rh、Ir、Pt、Cu 和 Ag 的速率决定步骤被推断为硝酸盐还原为亚硝酸盐，这从塔菲尔斜率、硝酸盐动力学反应级数和阴离子效应中可以明显看出。 Pt 转移实验表明，化学吸附的一氧化氮是硝酸盐还原的关键表面中间体。由于 Pt 和 Rh 的在线质谱 (DEMS) 测量显示没有形成一氧化氮 (NO)、一氧化二氮 (N2O) 或氮气 (N-2) 等气态产物，因此表明氨和羟胺是过渡金属电极上的主要产物。这与已知的 NO 还原机制一致，只有当 NO 存在于溶液中时才会形成 N2O 或 N-2。对于 Cu，DEMS 测量显示会产生气态 NO，这是因为与过渡金属相比，NO 与 Cu 的结合较弱。 (C) 2002 Elsevier Science B.V. 保留所有权利。
A comparative study was performed to determine the reactivity of nitrate ions at 0.1 M on eight different polycrystalline electrodes (platinum, palladium, rhodium, ruthenium, iridium, copper, silver and gold) in acidic solution using cyclic voltammetry (CV), chronoamperometry and differential electrochemical mass spectroscopy (DEMS). Cyclic voltammetry shows that the current densities for nitrate reduction depend strongly on the nature of the electrode. The activities decrease in the order Rh > Ru > Ir > Pd and Pt for the transition-metal electrodes and in the order Cu > Ag > Au for the coinage metals. The rate-determining step on Ru, Rh, Ir, Pt, Cu, and Ag is concluded to be the reduction of nitrate to nitrite, as is evident from the Tafel slope, the kinetic reaction order in nitrate, and the anion effect. Transfer experiments with Pt suggest that chemisorbed nitric oxide is the key surface intermediate in the nitrate reduction. Since on-line mass spectrometry (DEMS) measurements on Pt and Rh show no formation of gaseous products such as nitric oxide (NO), nitrous oxide (N2O) or nitrogen (N-2), it is suggested that ammonia and hydroxylamine are the main products on transition-metal electrodes. This is in agreement with the known mechanism for NO reduction, which forms N2O or N-2 only if NO is in solution. On Cu, DEMS measurements show the production of gaseous NO, which is explained by the weaker binding of NO to Cu as compared to the transition metals. (C) 2002 Elsevier Science B.V. All rights reserved.