Supported
Ni-based nanocatalysts have attracted much attention
to replace noble metal catalysts (e.g., IrO2) for the oxygen
evolution reaction (OER) due to their low costs. However, their low
activity is the main hindrance for their use in the practical OER
application. In this study, a Ni-based core–shell material
(Ni@Ni-NC) is produced through the heat treatment of a mixture of
urea and NiCl2·(H2O)6. Multiple
analysis data reveal that the Ni@Ni-NC consists of a Ni nanoparticle
core and several tens of nanometer-thick, N-doped carbon (NC) shell
materials, in which atomically attached Ni-based species were homogeneously
distributed. Ni@Ni-NC exhibits excellent electrocatalytic OER performance
with over- and onset potentials of 371 mV and 1.51 V, respectively,
which are better than those of commercial IrO2. As control
samples, structural and electrochemical properties of various composites
(Ni nanoparticles + N-doped graphene, Ni nanoparticles + C3N4, atomically dispersed Ni on a C3N4 surface) and acid-treated Ni@Ni-NC are investigated. These experiments
reveal that the well-dispersed Ni–NC species and core–shell
structures play pivotal roles in improving the electrocatalytic OER
performance. Furthermore, density functional theory (DFT) calculations
suggest the dual-site OER mechanism of the Ni–NC active species
with a significantly low reaction barrier. The mechanisms for the
formation of core–shell structures are studied with control
samples, which are produced from different heating times, and DFT
calculation suggested that the core/shell structure formation is attributed
to the cohesive energy of the Ni particles and strong bonds between
the Ni and NC supports. This work provides a facile strategy for designing
supported Ni catalysts with core–shell architecture for electrocatalytic
reactions and other advanced applications.