posted on 2021-10-13, 03:13authored byChunguang Kuai, Cong Xi, Anyang Hu, Yan Zhang, Zhengrui Xu, Dennis Nordlund, Cheng-Jun Sun, Christopher A. Cadigan, Ryan M. Richards, Luxi Li, Cun-Ku Dong, Xi-Wen Du, Feng Lin
The surface of an electrocatalyst
undergoes dynamic chemical and
structural transformations under electrochemical operating conditions.
There is a dynamic exchange of metal cations between the electrocatalyst
and electrolyte. Understanding how iron in the electrolyte gets incorporated
in the nickel hydroxide electrocatalyst is critical for pinpointing
the roles of Fe during water oxidation. Here, we report that iron
incorporation and oxygen evolution reaction (OER) are highly coupled,
especially at high working potentials. The iron incorporation rate
is much higher at OER potentials than that at the OER dormant state
(low potentials). At OER potentials, iron incorporation favors electrochemically
more reactive edge sites, as visualized by synchrotron X-ray fluorescence
microscopy. Using X-ray absorption spectroscopy and density functional
theory calculations, we show that Fe incorporation can suppress the
oxidation of Ni and enhance the Ni reducibility, leading to improved
OER catalytic activity. Our findings provide a holistic approach to
understanding and tailoring Fe incorporation dynamics across the electrocatalyst–electrolyte
interface, thus controlling catalytic processes.