Guo Xiaojun, Wang Ni, Li Xialiang, Zhang Zongyao, Zhao Jianping, Ren Wanjie, Ding Shuping, Xu Gelun, Li Jianfeng, Apfel Ulf-Peter, Zhang Wei, Cao Rui
Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an, 710119, China.
Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.
Angew Chem Int Ed Engl. 2020 Jun 2;59(23):8941-8946. doi: 10.1002/anie.202002311. Epub 2020 Mar 24.
Several H-H bond forming pathways have been proposed for the hydrogen evolution reaction (HER). Revealing these HER mechanisms is of fundamental importance for the rational design of catalysts and is also extremely challenging. Now, an unparalleled example of switching between homolytic and heterolytic HER mechanisms is reported. Three nickel(II) porphyrins were designed and synthesized with distinct steric effects by introducing bulky amido moieties to ortho- or para-positions of the meso-phenyl groups. These porphyrins exhibited different catalytic HER behaviors. For these Ni porphyrins, although their 1e-reduced forms are active to reduce trifluoroacetic acid, the resulting Ni hydrides (depending on the steric effects of porphyrin rings) have different pathways to make H . Understanding HER processes, especially controllable switching between homolytic and heterolytic H-H bond formation pathways through molecular engineering, is unprecedented in electrocatalysis.
对于析氢反应（HER），已经提出了几种形成H-H键的途径。揭示这些HER机制对于合理设计催化剂至关重要，同时也极具挑战性。现在，报道了一个在均裂和异裂HER机制之间切换的无与伦比的例子。通过将庞大的酰胺基部分引入到中位苯基的邻位或对位，设计并合成了三种具有不同空间效应的镍（II）卟啉。这些卟啉表现出不同的催化HER行为。对于这些镍卟啉，尽管它们的单电子还原形式对还原三氟乙酸具有活性，但生成的镍氢化物（取决于卟啉环的空间效应）形成H的途径不同。了解HER过程，特别是通过分子工程在均裂和异裂H-H键形成途径之间进行可控切换，在电催化中是前所未有的。
