Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex
Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex
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DOI：
10.1021/acscatal.1c01395
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发表时间：
2021-06-04
期刊：
影响因子：
12.9
通讯作者：
Gunnoe, T. Brent
中科院分区：
文献类型：
--
作者：
Geer, Ana M.;Musgrave, Charles, III;Gunnoe, T. Brent
报道了一种三核铜(II)配合物[(DAM)Cu-3(Mu(3)-O)][Cl]4(1，DAM=十二氮杂大四环)，作为均相电催化剂，在pH分别为7.0、8.1和11.5的磷酸盐缓冲溶液中催化水氧化制二氧化氧。PH为7时，过电位为550 mV时发生电催化水氧化，其翻转频率与1.5V时的19 S(-1)相近。在pH为11.5、电压为1.2V、pH为8.1、电压为1.37V、电解时间为40min的条件下，控制电位电解(CPE)实验证实了氧气的析出，法拉第效率分别为81%和45%。在CPE研究之后进行的漂洗测试为催化的均质性质提供了证据。电流密度与催化剂浓度的线性关系表明，铜预催化剂1可能是一级依赖关系，而动力学同位素研究(H2O和D2O)表明，质子参与了速率决定步骤或之前的步骤。在pH为8.1和11.2时，转环-圆盘电极的测量结果表明，没有H_2O_2生成的证据，支持选择性地生成氧气。电解过程中的冷冻猝灭电子顺磁共振研究为分子铜中间体的形成提供了证据。实验和计算研究支持磷酸盐作为受体碱的关键作用。此外，密度泛函理论计算强调了第二球相互作用的重要性以及氮基配体在促进质子转移过程中的作用。
We report a trinuclear copper( II) complex, [(DAM)Cu-3(mu(3)-O)][Cl] 4 (1, DAM = dodecaaza macrotetracycle), as a homogeneous electrocatalyst for water oxidation to dioxygen in phosphate-buffered solutions at pH 7.0, 8.1, and 11.5. Electrocatalytic water oxidation at pH 7 occurs at an overpotential of 550 mV with a turnover frequency of similar to 19 s(-1) at 1.5 V vs NHE. Controlled potential electrolysis (CPE) experiments at pH 11.5 over 3 h at 1.2 V and at pH 8.1 for 40 min at 1.37 V vs NHE confirm the evolution of dioxygen with Faradaic efficiencies of 81% and 45%, respectively. Rinse tests conducted after CPE studies provide evidence for the homogeneous nature of the catalysis. The linear dependence of the current density on the catalyst concentration indicates a likely first-order dependence on the Cu precatalyst 1, while kinetic isotope studies (H2O versus D2O) point to involvement of a proton in or preceding the rate-determining step. Rotating ring-disk electrode measurements at pH 8.1 and 11.2 show no evidence of H2O2 formation and support selectivity to form dioxygen. Freeze-quench electron paramagnetic resonance studies during electrolysis provide evidence for the formation of a molecular copper intermediate. Experimental and computational studies support a key role of the phosphate as an acceptor base. Moreover, density functional theory calculations highlight the importance of second-sphere interactions and the role of the nitrogen-based ligands to facilitate proton transfer processes.