Self-Composition of Hierarchical Core–Shell-Structured NiCo<sub>2</sub>O<sub>4</sub>@NiCo<sub>2</sub>O<sub>4</sub> Microspheres with Oxygen Vacancies for Efficient Oxygen Evolution Electrocatalysis
Jun Zhao, Feng-Wei Chen, Xiaoying Zhao, Xiaojing Wang, Yupei Li, Fa‐tang Li
Abstract
The reactivity of oxygen evolution reaction (OER) electrocatalysts can be effectively controlled by the subtle design of their morphologies, composition, and surface defects. Herein, the hierarchical core–shell-structured NiCo 2 O 4 @NiCo 2 O 4 microspheres (NCO-2) are synthesized by a “self-composition” strategy in the one-pot hydrothermal process followed by calcination. The unique nanoarchitecture of NCO-2 has NiCo 2 O 4 solid microspheres as the core and ultrathin porous NiCo 2 O 4 nanosheets as the shell, acting synergistically with the surface oxygen vacancies, which can afford more efficient active sites and shorten the transportation/diffusion path for electrons and electrolyte ions, thus evidently optimizing the OER kinetics. Consequently, the obtained NCO-2 exhibits significant electrocatalytic activity with a low overpotential of ∼350 mV and long-term stability of 30 h at 10 mA cm –2 in a 1.0 M KOH electrolyte, which outperforms those of NiCo 2 O 4 with diverse morphologies (solid sphere, urchin-like, and hollow structures) and commercial IrO 2 . This approach provides a promising route to design intricate catalyst structures for OER applications.