The new progress in in-situ/operando electrochemical Mössbauer spectroscopy research

Recently, our Center used the self-developed in-situ/operando electrochemical Mössbauer spectroscopy device to conduct an in-depth exploration of the mechanism of Ni-Fe based catalysts in the electrocatalytic oxygen evolution reaction (OER). A large amount of Fe4+ was first observed near the onset potential of OER through experiments, and it was further confirmed that the current density of OER is positively associated with the content of high-valent iron species which deepened people's understanding the reaction mechanism of Fe sites of Ni-Fe based catalysts in the OER reaction.

The research of electrocatalytic oxygen evolution materials is of great significance to the development of hydrogen energy and metal-air batteries. However, most of catalyst for commercialization are Ru, Ir-based and other noble metal catalysts. The development of non-precious metal OER catalysts with excellent performance and low price has been a hot research topic in recent years. At the same time, using in-situ/operando Mössbauer spectroscopy and other methods to study the reaction mechanism of OER materials to guide the synthesis of high-performance OER catalyst materials has become an important means to explore OER materials. For Ni-Fe oxyhydroxide OER catalysts, in-situ/operando Mössbauer spectroscopy studies have been reported, and it is found that there are indeed high-valent iron species in the reaction, but it is observed that it is generated at a relatively higher potential, which is much higher than OER. It is also reported that the kinetics can’t effectively promote the OER reaction. (JACS,

In this work, we used Prussian blue analogues as precursors to prepare Ni-Fe oxyhydroxide with low crystallinity through topological transformation, which has a high OER activity. And it was first discovered that a large amount of Fe4+(1.42 V vs. RHE, 12%) was formed near the OER starting potential by in-situ/operando electrochemical Mössbauer spectroscopy technology. As the voltage increased, its content can reach 40% (1.57 V vs. RHE). Through systematic research, the research group first confirmed experimentally that the current density of OER is positively correlated with the content of high-valent iron species (Fe4+), and deepened people's understanding of the reaction mechanism of Ni-Fe oxyhydroxide in OER.

Related work was published in full text in the Journal of Energy Chemistry and it was selected as the cover story ( This study is financially supported by the International Partnership Program of Chinese Academy of Sciences (No.121421KYSB20170020).