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A Copper-Peptoid as a Highly Stable, Efficient, and Reusable Homogeneous Water Oxidation Electrocatalyst
ACS Catalysis ( IF 12.9 ) Pub Date : 2018-09-28 00:00:00 , DOI: 10.1021/acscatal.8b03661
Totan Ghosh 1 , Pritam Ghosh 1 , Galia Maayan 1
Affiliation  

Water electrolysis is among the simplest methods to generate hydrogen, which can be used as a clean and renewable energy source. Within this process, the oxidation of water into molecular oxygen is considered as the bottleneck reaction because it involves the transfer of four electrons toward the oxidation of a highly stable small molecule. Challenges in this area include the development of stable and effective electro- and photocatalysts that utilize readily available metal ions. Herein we report a copper–peptidomimetic complex as an electrocatalyst for water oxidation, which is both highly stable and efficient. Inspired by enzymatic catalysis, which is largely based on intramolecular cooperativity between a metal center and functional organic molecules located on one scaffold, we have designed and synthesized a peptoid trimer bearing a 2,2′-bipyridine (bipy) ligand, an −OH group, and a benzyl group. Both experimental and computational data reveal that binding of CuII to this peptoid in aqueous medium occurs via the bipy group and two hydroxyl moieties from the solution. Based on a systematic electrochemical study, we show that this complex is an active electrocatalyst for water oxidation in aqueous phosphate buffer solution enabling oxygen evolution at pH 11.5 with a turnover frequency of 5.8 s–1 and a Faradaic efficiency of up to 91%. Importantly, this catalyst is highly stable over at least 15 h of electrolysis. Thus, we could reuse it for at least 9 times in 40 min electrolysis experiments, demonstrate that it retains its activity in every experiment, and obtain oxygen evolution with an overall turnover number record (based on moles oxygen to moles catalyst) of >56 in 6 h. Moreover, based on electrochemical experiments, spectroscopic data, and density functional theory-D3 calculations, we identified a key peroxo intermediate and propose an intramolecular cooperative catalytic path for this reaction, which suggests that the −OH group has a major role in the high stability of the complex.

中文翻译:

铜拟肽作为高度稳定,高效和可重复使用的均相水氧化电催化剂

水电解是产生氢的最简单方法之一,可以用作清洁和可再生的能源。在此过程中,将水氧化为分子氧被认为是瓶颈反应,因为它涉及四个电子向高度稳定的小分子的氧化转移。该领域的挑战包括开发利用容易获得的金属离子的稳定有效的电催化剂和光催化剂。在这里,我们报告了铜-拟肽络合物作为水氧化的电催化剂,它既稳定又高效。受酶催化的启发,酶催化主要是基于金属中心与位于一个支架上的功能性有机分子之间的分子内协同作用,我们设计并合成了带有2个类肽的三聚体 2'-联吡啶(联吡啶)配体,-OH基和苄基。实验和计算数据均表明,铜的结合在水介质中该类肽的II通过联吡啶基和溶液中的两个羟基部分产生。基于系统的电化学研究,我们表明该络合物是一种在磷酸盐缓冲液中用于水氧化的活性电催化剂,能够在pH为11.5的条件下以5.8 s –1的周转频率释放氧气。法拉第效率高达91%。重要的是,该催化剂在至少15小时的电解过程中具有很高的稳定性。因此,我们可以在40分钟的电解实验中将其重复使用至少9次,证明它在每个实验中均保持其活性,并在> 56的条件下获得的氧气逸出量总记录(基于氧气与催化剂的摩尔数)为56。 6小时 此外,基于电化学实验,光谱数据和密度泛函理论-D3计算,我们确定了一个重要的过氧中间体,并提出了该反应的分子内协同催化路径,这表明-OH基团在高稳定性中起主要作用。的复杂。
更新日期:2018-09-28
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