In a polycrystalline material, the grain boundaries (GBs) can be effective active sites for catalytic reactions by providing an electrodynamically favorable surface. Previous studies have shown that grain boundary density is related to the catalytic activity of the carbon dioxide reduction reaction, but there is still no convincing evidence that the GBs provide surfaces with enhanced activity for oxygen evolution reaction (OER). Combination of various electrochemical measurements and chemical analysis reveals the GB density at surface of NiFe electrocatalysts directly affects the overall OER. In situ electrochemical microscopy vividly shows that the OER occurs mainly at the GB during overall reaction. It is observed that the reaction determining steps are altered by grain boundary densities and the meaningful work function difference between the inside of grain and GBs exists. High-resolution transmission electron microscopy shows that extremely high index planes are exposed at the GBs, enhancing the oxygen evolution activity. The specific nature of GBs and its effects on the OER demonstrated in this study can be applied to the various polycrystalline electrocatalysts.
Bibliographical noteFunding Information:
H.K.P. and H.S.A. contributed equally to this work. This research was supported by the Future Material Discovery Program (Grant No. 2018M3D1A1058793), Basic Research Laboratory of the National Research Foundation of Korea (NRF) funded by the Ministry of Science and Information & Communication Technology (ICT) (MSIT), Korean government (2018R1A4A1022647), the NRF grant funded by the MSIT (2019M3E6A1103818), Basic Science Research Program through the NRF funded by MSIT (2017R1A2B3009135), and Institute of Engineering Research at the Seoul National University. C.‐H.L. acknowledges the support from the Korea University ‐ Korea Institute of Science and Technology (KU‐KIST) school project.
© 2020 Wiley-VCH GmbH
- NiFe alloys
- grain boundaries
- in situ electrochemical microscopy
- oxygen evolution reaction
ASJC Scopus subject areas
- General Chemistry
- General Materials Science