Impact of the NiO nanostructure morphology on the oxygen evolution reaction catalysis

The oxygen evolution reaction (OER) is still a barrier to energy generation technologies, motivating the development of new strategies to the rational use of electrodes for OER. This work reports the effect of the morphology of nickel oxide (NiO) nanostructures on their catalytic activity toward OER in alkaline medium. 1D hollow nanofibers (NiO-NFBs) synthesized by solution blow spinning are compared with 3D nanoparticles (NiO-NPTs) synthesized by a well-known citrate method. The intrinsic activity of the electrocatalysts was evaluated by linear sweep voltammetry (LSV), electrochemically active surface area (ECSA), turnover frequency (TOF), and electrochemical impedance spectroscopy (EIS). Results confirm the superiority of NiO-NFBs, with a remarkable difference of 133 mV versus RHE to generate j = 10 mA cm−2. The NiO-NFBs showed a TOF value 122 times higher than NiO-NPTs. The Tafel analysis and EIS revealed that the hollow structure favors kinetics through a more efficient process of mass and charge transfer. Overall, results corroborate the thesis that the morphology imposes the main rule on the electrocatalyst performance. The morphology of NiO-NFBs is fully preserved after the electrolysis test, while NiO-NPTs degrade through a nanoparticle coalescence mechanism. This work is a contribution to the state of the art of nanostructured NiO-based electrodes for OER.