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The electrochemistry of Sn(II), Sn(IV), and Se(IV) in the choline chloride-glycerol deep eutectic solvent was investigated on glassy carbon at 110 °C by various electrochemical methods including cyclic voltammetry, chronopotentiometry, and chronoamperometry. The Sn(IV)/Sn(II) couple displays very slow electrochemical kinetics, so that the reduction of Sn(IV) essentially proceeds directly to Sn(0) through a 4 e− process, even if the potential of the Sn(IV)/Sn(II) couple is more positive than the Sn(II)/Sn(0) couple. Because of this sequence of potentials, the comproportionation reaction Sn(IV) + Sn(0) → 2Sn(II) takes place when elemental tin is deposited from the Sn(IV) solution. The electrodeposition of tin proceeds through an instantaneous nucleation process with Sn(II) whereas a progressive nucleation mechanism is observed with Sn(IV). In the presence of both Sn(IV) and Se(IV) in solution, voltammetric features associated with the formation of a Sn-Se compound are clearly identified and the suitable potential range where the compound can be deposited without co-deposition of elemental tin is determined, as confirmed by SEM images and EDX analyses. [ABSTRACT FROM AUTHOR]

Electrochemical nucleation and growth (EN&G) is an inherently dynamic process governed by atomic-level interactions. Understanding the electrochemical phase formation on foreign substrates presents a formidable challenge at the fundamental level. One of the main challenges lies in uncovering both the energetic state of the substrate and the complex interaction between the substrate and the newly formed phase at the "electrode–electrolyte" interface. Furthermore, obtaining direct, unconvoluted, information is not straightforward due to the intricate nature of the phase boundary and phase formation process. In this work, we explore the EN&G from a local perspective by independently probing hundreds of different surface regions with scanning electrochemical cell microscopy (SECCM), providing a novel perspective and insights into the activity distribution and role of the substrate state in the nucleation process. We highlight the significance of acknowledging the diversity at the microscopic scale by summarizing the electrochemical profiles with statistical measures and observing their temporal- or potential-dependent evolution. Our results show that the energy required for the formation of stable nuclei on active sites varies due to surface heterogeneities, significantly impacting the overpotential required on low-energy and high-energy substrates. Upon a cross-system examination, trends emerge thanks to our high-throughput approach. Although nucleation is driven by the most active sites, we observe that it is possible to probe less active sites. Interestingly, these can significantly change their activity after being subjected to polarization. Non-uniform distributions of nucleation activity are disclosed and can be best fitted with two expressions: lognormal and Weibull. The understanding of these distributions is the bridge connecting the microscopic information to macroscopic outcomes, shedding light on how surface heterogeneities influence nucleation rates and deposition behaviors. Characterizing the distribution provides valuable insights into the underlying mechanism, offering a deeper understanding of the nature of active sites and highlighting the capabilities of our local approach for leveraging data-driven analysis. [ABSTRACT FROM AUTHOR]

A hybrid rule-based/ML approach using linear regression and artificial neural networks (ANNs) determined pitting corrosion descriptors from high-throughput data obtained with Scanning Electrochemical Cell Microscopy (SECCM) on 316 L stainless steel. Non-parametric density estimation determined the central tendencies of the Epit/log(jpit) and Epass/log(jpass) distributions. Descriptors estimated using conditional mean or median curves were compared to their central tendency values, with the conditional medians providing more accurate results. Due to their lower sensitivity to high outliers, the conditional medians were more robust representations of the log(j) vs. E distributions. An observed trend of passive range shortening with increasing testing aggressiveness was attributed to delayed stabilisation of the passive film, rather than early passivity breakdown. [ABSTRACT FROM AUTHOR]