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.
At the same time, in-situ/operando Mossbauer spectroscopy was used to study the reaction mechanism of oxygen evolution reaction (OER) materials, in order to guide the synthesis of high-performance OER catalyst materials.
Recently, a group led by prof. WANG Junhu from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with prof. HUANG Yanqiang from DICP, used the self-developed in-situ/operando electrochemical Mossbauer spectroscopy device to investigate the mechanism of Ni-Fe based catalysts in the electrocatalytic OER. They observed a large amount of Fe4+ near the onset potential of OER through experiments, and further confirmed that the current density of OER was positively associated with the content of high-valent iron species.
This study was published in the Journal of Energy Chemistry and it was selected as cover article.
Constructed nickel–iron (oxy)hydroxide with abundant in-situ produced high-valent iron species for efficient water oxidation (Image by KUANG Zhichong)
In this work, the researchers used Prussian blue analogues as precursors to prepare Ni-Fe oxyhydroxide with low crystallinity through topological transformation, which had a high OER activity. They discovered that a large amount of Fe4+ was formed near the OER starting potential by in-situ/operando electrochemical Mossbauer spectroscopy technology. As the voltage increased, its content could reach 40%.
"We first confirmed experimentally that the current density of OER was positively correlated with the content of high-valent iron species (Fe4+), and it deepened our understanding of the reaction mechanism of Ni-Fe oxyhydroxide in OER," said Prof. WANG.
This study is supported by the International Partnership Program of CAS. (Text by by KUANG Zhichong)