Temperature‐Dependent Synthesis of Robust Ultrathin Cobalt Oxide Nanomesh for Oxygen Evolution Reaction

Abstract A temperature‐dependent annealing methodology has been developed for the synthesis of ultrathin Co 3 O 4 nanomesh that has pores on the basal planes of nanosheets. The high‐temperature annealing resulted in situ exfoliation and etching that created narrow mesopores (3–5.5 nm) on the basal plane. N 2 adsorption/desorption and transmission electron microscopy experiments validated the formation of nanomeshes, and the best material (CoNM‐400) was obtained at 400 °C annealing temperature. The CoNM‐400 revealed superior catalytic performance for oxygen evolution reaction with an overpotential of 308 mV, a mass activity of 396.7 A g −1 , and a turnover frequency of 6.15 s −1 . Electrochemical impedance spectroscopy revealed a minimal charge transfer resistance (4.2 Ω) and pseudoresistance (66.2 Ω), favoring effective electron transport at the electrode/electrolyte interface and improved kinetics for oxygen evolution reaction, respectively. The elevated roughness factor of around 325 underscored the significance of small mesopores in enhancing catalyst–electrolyte interactions and enhancing mass transport inside the material. CoNM‐400 exhibited exceptional stability for 10 days of prolonged electrolysis at a current density of 30 mA cm − 2 . The stability of the material was due to the presence of narrow mesopores on the basal plane of the ultrathin nanosheets that favored vertical ion penetration and easy O 2 release, and the uniformly distributed mesopores served as an efficient buffer to mitigate volume expansion during intense electrocatalysis. The polycrystalline nature of the nanomesh also provided structural robustness to sustain intense electrocatalysis with high gas evolution.