Ir-Induced Local Charge and Electron-Spin Regulation on CoNi LDH Electrocatalyst for Efficient Oxygen Evolution Reaction

Nonprecious metal CoNi layered double hydroxides (LDHs)
have received
extensive attention as binary LDH-type catalysts with the lowest overpotential
in the oxygen evolution reaction (OER). However, its relatively low
electrical conductivity and strong adsorption on oxygen-containing
intermediates limit the OER reaction rate. Therefore, we doped the
iridium element containing 5d orbitals into CoNi LDH and obtained
the ternary CoNiIr ZLDH (ZIF-67 derived LDH) electrocatalyst with
an efficient OER performance. This strategy reduces the initial overpotential
of the OER reaction. Only low overpotentials of 202 mV and 280 mV
are needed to achieve current densities of 10 mA cm–2 and 100 mA cm–2, respectively. Furthermore, this
electrode exhibits strong electrochemical stability and maintains
the minimum degradation for nearly 24 h under the harsh OER conditions
with a high current density of 60 mA cm–2. These
characteristics make CoNiIr ZLDH one of the most efficient CoNi-based
LDH catalysts reported to date. Density functional theory calculations
indicate that the high catalytic activity of CoNiIr ZLDH mainly results
from the spin–orbit coupling effect of the wide 5d-orbital
containing element Ir, which alters the electron charge and electron
spin distribution near the Fermi energy of the catalyst. This modification
enhances the electrical conductivity, reduces the adsorption energy
of oxygen species, and promotes the transfer of electrons and substances,
thereby lowering the reaction overpotential and improving the reaction
efficiency. This research is expected to provide new ideas for the
practical design of OER electrodes in electrochemical water splitting.