Multi-potential-step chronocoulospectrometry for electrocatalytic water oxidation by a mononuclear ruthenium aquo complex immobilized on a mesoporous ITO electrode
Multi-potential-step chronocoulospectrometry for electrocatalytic water oxidation by a mononuclear ruthenium aquo complex immobilized on a mesoporous ITO electrode
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通过固定在介孔 ITO 电极上的单核钌水复合物进行电催化水氧化的多电位步骤计时库仑光谱法
DOI：
10.1039/c9dt04442f
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
and Masayuki Yagi
中科院分区：
文献类型：
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作者：
Yuta Tsubonouchi;Junichiro Honta;Taisei Sato;Eman A. Mohamed;Zaki N. Zahran;Kenji Saito;Tatsuto Yui;and Masayuki Yagi
以4，4 ′-二羧基-2，2 ′-联吡啶（H2 dcbpy）和4′-辛氧基-2，2 ′：6′，2 ′ ′-三联吡啶（C8 Otpy）为配体，合成了一种新的单核钌水配合物[Ru（C8 Otpy）（H2 dcbpy）（OH 2）]2+，并将其固定在介孔铟掺杂氧化锡（meso-ITO）电极上，采用多电位阶跃计时库仑法（MPSCCS）研究了该配合物对水的电催化氧化.紫外-可见吸收光谱数据表明，即使在pH 5.9的电解质溶液中，[Ru（C8 Otpy）（dcbpy）（OH 2）]（RuOH 2）在meso-ITO表面上也被去质子化为[Ru（C8 Otpy）（dcbpy）（OH）]−（RuOH）。RuOH/meso-ITO电极的循环伏安图（CV）显示在pH 5- 1/2范围内在E1/2 = 0.80 V vs. Ag/AgCl处的pH无关的氧化还原响应，被归因于RuIIOH/RuIIIOH的非质子耦合的1 e −氧化还原过程。对RuOH/meso-ITO电极在0.2 ~ 1.5 V（Ag/AgCl）之间的MPSCCS测量表明，RuIV物种（暂称RuIVO）在电催化的初始阶段以稳态存在。这表明在所采用的条件下，从RuIVO到RuVO的电化学氧化可以与水亲核攻击竞争参与速率决定步骤中的O-O键形成。水对RuIVO的亲核攻击也可能与RuIVO到RuVO的电化学氧化竞争的可能性被建议由电催化水氧化在低施加电位1.4 V之前的RuVO的形成电位。在1.4V下持续1小时的MPSCCS测量显示，RuOH在电极上逐渐转化为替代催化剂（最可能是RuOx纳米颗粒）。MPSCCS技术是有前途的，以揭示氧化还原反应和固定在电极上的分子催化剂的催化方面的水氧化。
A new mononuclear Ru aquo complex [Ru(C8Otpy)(H2dcbpy)(OH2)]2+ with 4,4′-dicarboxy-2,2′-bipyridine (H2dcbpy) and 4′-octyloxy-2,2′:6′,2′′-terpyridine (C8Otpy) ligands was synthesized to investigate electrocatalytic water oxidation by the complex immobilized on a mesoporous indium-doped tin oxide (meso-ITO) electrode using a multi-potential-step chronocoulospectrometric (MPSCCS) technique. UV-visible absorption spectroscopic data indicated that [Ru(C8Otpy)(dcbpy)(OH2)] (RuOH2) is deprotonated to [Ru(C8Otpy)(dcbpy)(OH)]− (RuOH) on the meso-ITO surface even at pH 5.9 of the electrolyte solution. The cyclic voltammogram (CV) of the RuOH/meso-ITO electrode showed a pH-independent redox response at E1/2 = 0.80 V vs. Ag/AgCl in the pH range of 5–12, being assigned to a non-proton-coupled 1e− redox process of RuIIOH/RuIIIOH. The MPSCCS measurement of the RuOH/meso-ITO electrode between 0.2 and 1.5 V vs. Ag/AgCl showed that RuIV species (tentatively RuIVO) exist in a steady state of the electrocatalysis in the initial stage. This suggests that the electrochemical oxidation from RuIVO to RuVO could compete with the water nucleophilic attack for O–O bond formation involved in the rate-determining step under the employed conditions. The possibility that the water nucleophilic attack on RuIVO could also compete with the electrochemical oxidation of RuIVO to RuVO was suggested by the electrocatalytic water oxidation at a low applied potential of 1.4 V prior to the formation potential of RuVO. The MPSCCS measurement at 1.4 V for 1 h showed that RuOH is gradually transformed into an alternative catalyst (most likely RuOx nanoparticles) on the electrode. The MPSCCS technique is promising to reveal the redox reactions and catalytic aspects of molecular catalysts immobilized on an electrode for water oxidation.