Electronic Factors Influencing the Thermodynamics of the Oxygen Evolution Reaction in Layered Double Hydroxides with Oxygen Vacancies

Oxygen
vacancies (Ovac) in layered double hydroxides
(LDHs) are point defects that significantly influence the electronic
structure and catalytic properties of these materials, enhancing their
suitability for electrocatalysis. The bimetallic nature of LDHs enables
precise tuning of these properties, making them adaptable to specific
applications such as the oxygen evolution reaction (OER). Despite
known improvements in catalytic activity due to Ovac, the
interplay between Ovac, material composition, and critical
properties like adsorption energy remains insufficiently understood.
Herein, density functional theory (DFT) calculations were employed
to investigate the impact of Ovac on the electronic and
catalytic properties of nickel-based LDH surfaces with varying compositions
(NiM, where M = Mn, Fe, Co, and Cu) in the context of the OER. The
calculations reveal a strong correlation between properties such as
magnetic moment, adsorption energy, and thermodynamic overpotential
with the position of the d-band center. Introducing Ovac reduces theoretical overpotential across all compositions by shifting
the d-band center to more negative energies relative to the Fermi
level, lowering binding energy and charge transfer to adsorbed species.
NiFe-Ovac demonstrates an optimal balance of overpotential
and adsorption energy, while NiMn-Ovac and NiCo-Ovac present a moderate relationship between these two quantities. Meanwhile,
NiCu’s performance deviates significantly, indicating low OER
activity. These findings offer insights for designing efficient LDH-based
catalysts through defect engineering and compositional optimization.