Ni/NiO/C hollow microspheres fabricated by a mist-CVD process using ethanolamine: an efficient OER catalyst

NiO-based materials hold great promise as oxygen evolution reaction (OER) catalysts owing to their high intrinsic OER activity and good chemical stability. Herein, Ni/NiO/C hollow microspheres with high activity were successfully fabricated through a facile one-step mist chemical vapor deposition (mist-CVD) process using ethanolamine and nickel chloride as precursors. The high-temperature pyrolysis of the organic precursor yields a significant quantity of gas, leading to a rapid increase in pressure within the droplet, which prompts the nanoparticles to aggregate on the surface of the droplet and form a hollow structure. The crystal phase and morphology of the samples can be modulated through optimizing the decomposition temperature, and particularly, Ni/NiO/C porous hollow microspheres synthesized at 600 °C (Ni-600) presented the best OER activity, exhibiting an overpotential at 10 mA cm−2 (η10) of 286.4 mV and a Tafel slope of 54.8 mV dec−1. The outstanding OER electrocatalytic performance of Ni/NiO/C hollow microspheres is ascribed to the improved electronic conductivity facilitated by the existence of metallic Ni and amorphous C, coupled with the relatively large specific surface area derived from the unique hollow structure.