Ultramicroelectrode Studies of Self-Terminated Nickel Electrodeposition and Nickel Hydroxide Formation upon Water Reduction.
Ultramicroelectrode Studies of Self-Terminated Nickel Electrodeposition and Nickel Hydroxide Formation upon Water Reduction.
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DOI：
10.1021/acs.jpcc.6b10006
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发表时间：
2016-12-08
期刊：
影响因子：
--
通讯作者：
Moffat TP
中科院分区：
文献类型：
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作者：
Ritzert NL;Moffat TP
利用超微电极(UME)结合光学成像、产生/收集扫描电化学显微镜(G/C-SECM)和初步的微尺度pH测量，在确定的传质条件下研究了电沉积镍与电解液破裂之间的相互作用，即通过H3O+和H2O还原的析氢反应(HER)。在5 mmoL/L NiCl2+0.1mol/L NaC l，pH 3.0的电解液中，在−0.6V~−1.4V与Ag/AgCl2之间的中等过电位下的伏安电流分布在金属沉积和H3O+还原之间，两个反应都达到传质极限电流值。在更负的电位下，在H2O还原开始时出现不寻常的电流尖峰，并伴随着氢气产量的瞬时增加。电流峰电位是[Ni(H2O)6]2+(Aq)浓度和pH的函数。电流的急剧上升归因于自催化H2O还原的开始，电化学生成的OH−物种诱导了Ni(OH)2(ADS)岛的异相成核，据报道，岛的周长对H2O还原具有活性。随着涂层的结合，进一步的金属沉积被淬灭，同时H2O还原继续进行，尽管速度有所下降，因为最活跃的位置，例如Ni/Ni(OH)2岛边缘，可用。当电位低于−1.5V与Ag/AgCl时，H2O还原被加速，导致Ni(OH)2·xH2O在UME的近半球形扩散层内均匀析出。
The interaction between electrodeposition of Ni and electrolyte breakdown, namely the hydrogen evolution reaction (HER) via H3O+ and H2O reduction, was investigated under well-defined mass transport conditions using ultramicroelectrodes (UME’s) coupled with optical imaging, generation/collection scanning electrochemical microscopy (G/C-SECM), and preliminary microscale pH measurements. For 5 mmol/L NiCl2 + 0.1 mol/L NaCl, pH 3.0, electrolytes, the voltammetric current at modest overpotentials, i.e., between −0.6 V and −1.4 V vs. Ag/AgCl, was distributed between metal deposition and H3O+ reduction, with both reactions reaching mass transport limited current values. At more negative potentials, an unusual sharp current spike appeared upon the onset of H2O reduction that was accompanied by a transient increase in H2 production. The peak potential of the current spike was a function of both [Ni(H2O)6]2+(aq) concentration and pH. The sharp rise in current was ascribed to the onset of autocatalytic H2O reduction, where electrochemically generated OH− species induce heterogeneous nucleation of Ni(OH)2(ads) islands, the perimeter of which is reportedly active for H2O reduction. As the layer coalesces, further metal deposition is quenched while H2O reduction continues albeit at a decreased rate as fewer of the most reactive sites, e.g., Ni/Ni(OH)2 island edges, are available. At potentials below −1.5 V vs. Ag/AgCl, H2O reduction is accelerated, leading to homogeneous precipitation of bulk Ni(OH)2·xH2O within the nearly hemispherical diffusion layer of the UME.