3D electrode surface engineering via atomic layer deposition of nickel oxide for improved water oxidation performance

Nickel-based electrodes are widely recognized for their cost-effectiveness and efficiency in the alkaline oxygen evolution reaction (OER), yet further advancements in surface engineering of these electrodes are essential to fully unlock their catalytic potential. This study explores the electrocatalytic performance of several topologies of 3D-structured nickel electrodes decorated by atomic layer deposited (ALD) NiO films for water oxidation. While pristine Ni electrodes already exhibit good performance due to their 3D structure, their native NiO layer is limited by its fixed thickness, chemical composition, and crystallinity. Adopting ALD for surface modification allows to unravel the role of these properties on the OER performance and electrochemical activation. Among the investigated structures in this work, the 3D Ni electrode based on regularly shaped pillars and holes (Ni Veco), stands out as the most promising OER electrocatalyst, both in its pristine state and after ALD NiO modification, surpassing the performance of Ni felt and Ni foam. Moreover, the presence of ALD NiO is demonstrated to significantly alter the surface chemistry and surface energy of Ni electrodes, leading to a notable enhancement of the OER performance. Upon electrochemical activation, thermal and plasma-assisted ALD NiO on Ni Veco demonstrated overpotentials of 470 and 560 mV, respectively, at 500 mA·cm^-2, outperforming pristine Ni Veco (640 mV).