Guo Si-Xuan, Lee Chong-Yong, Zhang Jie, Bond Alan M, Geletii Yurii V, Hill Craig L
School of Chemistry, Monash University Clayton, Victoria 3800, Australia.
Inorg Chem. 2014 Jul 21;53(14):7561-70. doi: 10.1021/ic500878w. Epub 2014 Jul 7.
The water insoluble complex Rb4[Ru(II)(bpy)3]5[{Ru(III)4O4(OH)2(H2O)4}(γ-SiW10O36)2], ([Ru(II)bpy]5[Ru(III)4POM]), was synthesized from Rb8K2[{Ru(IV)4O4(OH)2(H2O)4}(γ-SiW10O36)2] and used for electrocatalytic water oxidation under both thin- and thick-film electrode conditions. Results demonstrate that the [Ru(II)bpy]5[Ru(III)4POM] modified electrode enables efficient water oxidation to be achieved at neutral pH using thin-film conditions, with Ru(bpy)3([Ru(III)bpy]) acting as the electron transfer mediator and [Ru(V)4POM] as the species releasing O2. The rotating ring disc electrode (RRDE) method was used to quantitatively determine the turnover frequency (TOF) of the catalyst, and a value of 0.35 s(-1) was obtained at a low overpotential of 0.49 V (1.10 V vs Ag/AgCl) at pH 7.0. The postulated mechanism for the mediator enhanced catalytic water process in a pH 7 buffer containing 0.1 M LiClO4 as an additional electrolyte includes the following reactions (ion transfer for maintaining charge neutrality is omitted for simplicity): [Ru(II)bpy]5[Ru(III)4POM] → [Ru(III)bpy]5[Ru(V)4POM] + 13 e(-) and [Ru(III)bpy]5[Ru(V)4POM] + 2H2O → [Ru(III)bpy]5[Ru(IV)4POM] + O2 + 4H(+). The voltammetry of related water insoluble [Ru(II)bpy]2[S2M18O62] (M = W and Mo) and [Fe(II)Phen]x[Ru(III)4POM] materials has also been studied, and the lack of electrocatalytic water oxidation in these cases supports the hypothesis that [Ru(III)bpy] is the electron transfer mediator and [Ru(V)4POM] is the species responsible for oxygen evolution.
水不溶性配合物Rb4[Ru(II)(bpy)3]5[{Ru(III)4O4(OH)2(H2O)4}(γ-SiW10O36)2]，([Ru(II)bpy]5[Ru(III)4POM])，由Rb8K2[{Ru(IV)4O4(OH)2(H2O)4}(γ-SiW10O36)2]合成，并用于薄膜和厚膜电极条件下的电催化水氧化。结果表明，[Ru(II)bpy]5[Ru(III)4POM]修饰电极在薄膜条件下能在中性pH值下实现高效水氧化，Ru(bpy)3([Ru(III)bpy])作为电子转移介质，[Ru(V)4POM]作为释放O2的物种。采用旋转环盘电极（RRDE）方法定量测定催化剂的周转频率（TOF），在pH 7.0时，在0.49 V（相对于Ag/AgCl为1.10 V）的低过电位下得到的值为0.35 s(-1)。在含有0.1 M LiClO4作为附加电解质的pH 7缓冲液中，介质增强催化水过程的假定机制包括以下反应（为简单起见，省略了用于维持电荷中性的离子转移）：[Ru(II)bpy]5[Ru(III)4POM] → [Ru(III)bpy]5[Ru(V)4POM] + 13 e(-) 和 [Ru(III)bpy]5[Ru(V)4POM] + 2H2O → [Ru(III)bpy]5[Ru(IV)4POM] + O2 + 4H(+)。还研究了相关水不溶性[Ru(II)bpy]2[S2M18O62]（M = W和Mo）和[Fe(II)Phen]x[Ru(III)4POM]材料的伏安法，在这些情况下缺乏电催化水氧化支持了[Ru(III)bpy]是电子转移介质且[Ru(V)4POM]是负责析氧的物种的假设。
