Bai Lichen, Lee Seunghwa, Hu Xile
Laboratory of Inorganic Synthesis and Catalysis, Institute of Chemical Sciences and Engineering, ISIC-LSCI, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
Angew Chem Int Ed Engl. 2021 Feb 8;60(6):3095-3103. doi: 10.1002/anie.202011388. Epub 2020 Dec 11.
A bifunctional oxygen evolution reaction (OER) mechanism, in which the energetically demanding step of the attack of hydroxide on a metal oxo unit is facilitated by a hydrogen atom transfer to a second site, has the potential to circumvent the scaling relationship. However, the bifunctional mechanism has hitherto only been supported by theoretical computations. Here we describe an operando Raman spectroscopic and electrokinetic study of two highly active OER catalysts, FeOOH-NiOOH and NiFe layered double hydroxide (LDH). The data support two distinct mechanisms for the two catalysts: FeOOH-NiOOH operates by a bifunctional mechanism where the rate-determining O-O bond forming step is the OH attack on a Fe=O coupled with a hydrogen atom transfer to a Ni -O site, whereas NiFe LDH operates by a conventional mechanism of four consecutive proton-coupled electron transfer steps. The experimental validation of the bifunctional mechanism enhances the understanding of OER catalysts.
一种双功能析氧反应（OER）机制，其中氢原子转移到第二个位点促进了氢氧化物对金属氧代单元攻击这一能量需求较高的步骤，该机制有可能规避比例关系。然而，迄今为止，双功能机制仅得到理论计算的支持。在此，我们描述了对两种高活性OER催化剂FeOOH-NiOOH和镍铁层状双氢氧化物（LDH）的原位拉曼光谱和动电研究。数据支持这两种催化剂的两种不同机制：FeOOH-NiOOH通过双功能机制运行，其中决定反应速率的O-O键形成步骤是OH对Fe=O的攻击并伴有氢原子转移到Ni -O位点，而镍铁层状双氢氧化物通过四个连续的质子耦合电子转移步骤的传统机制运行。双功能机制的实验验证增进了对OER催化剂的理解。
