Nanoscale pyrazolate-based coordination polymers (CPs)
are becoming
increasingly popular as electrocatalysts owing to their customizable
compositions and structures. However, using them for oxygen evolution
reaction (OER) is highly challenging due to their unsatisfactory catalytic
efficiency and relatively low stability. Herein, a simple one-step
solvothermal process was employed for the fabrication of polycrystalline
nickel-pyrazolate [Ni(Pz)] with an unusual lamellar nanorod-assembled
microsphere morphology for the first time using ethanol as a green
organic solvent via controlling other physical parameters. Meanwhile,
the Ni(Pz) structure and morphology are investigated to derive its
formation process following the different monomeric feed ratios relying
on the metal/ligand interactions of CP. Shaping the Ni(Pz) electrocatalyst
in well-oriented lamellar nanorod-assembled microspheres brings the
advantage of porosity and high specific surface area, which expedites
mass/charge transport and contact with the electrolyte as well as
creates less tortuous pathways for charge distribution, thus improving
the charge homogeneity. These high-class structural features and polycrystalline
nature of Ni(Pz)-E-PVP facilitate amazing catalytic OER activity with
a low overpotential of 290 mV at 10 mA cm–2 and
a Tafel slope of only 94 mV dec–1 beyond the yardstick
material (i.e., RuO2) in alkaline solution. A suite of
measurements, entailing X-ray photoelectron spectroscopy and density
functional theory calculations, suggest that the rich Ni–N4 moieties in Ni(Pz)-E-PVP are central species providing adsorption
sites for OER intermediates. This facile protocol is prophesied to
commence the imminent development of noble metal-free, effective,
and low-priced electrocatalysts for OER.