Deciphering Competitive Routes for Nickel-Based Nanoparticle Electrodeposition by an Operando Optical Monitoring

Electrodeposition of earth-abundant iron group metals such as nickel is difficult to characterize by simple electrochemical analyses since the reduction of their metal salts often competes with inhibiting reactions. This makes the mechanistic interpretation sometimes contradictory, preventing unambiguous predictions about the nature and structure of the electrodeposited material. Herein, the complexity of Ni nanoparticles (NPs) electrodeposition on indium tin oxide (ITO) is unraveled operando and at a single entity NP level by optical microscopy correlated to ex situ SEM imaging. Our correlative approach allows differentiating the dynamics of formation of two different NP populations, metallic Ni and Ni(OH)(2) with a < 25 nm limit of detection, their formation being ruled by the competition between Ni2+ and water reduction. At the single NP level this results in a self-terminated growth, an information which is most often hidden in ensemble averaged measurements.

Automated summary

The electrodeposition of nickel nanoparticles on indium tin oxide (ITO) is complex and can be differentiated by optical microscopy and SEM imaging, revealing the dynamics of two different NP populations: metallic nickel and Ni(OH)(2). The formation of these NPs is governed by the competition between Ni2+ and water reduction, resulting in self-terminated growth at the single NP level. This information is often obscured in ensemble averaged measurements.