Deciphering Competitive Routes for Nickel‐Based Nanoparticle Electrodeposition by an Operando Optical Monitoring. Issue 31 (29th June 2021) - Godeffroy, Louis
Abstract: 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 Ni 2+ 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. Abstract : The results of electrodeposition can be challenging to predict in the absence of unambiguous electrochemical signature. Operando optical microscopy correlated to ex situ SEM imaging allows probing mechanistic diversity with single nanoparticle resolution. It is illustrated by differentiating, with sub‐25 nm size limit of detection, the electrodeposition of Ni and Ni(OH)2 NPs upon Ni 2+ reduction.