Differentiating electrochemically active regions of indium tin oxide electrodes for hydrogen evolution and reductive decomposition reactions. An in situ optical microscopy approach

Hybrid scanning electrochemical cell microscopy-interference reflection microscopy (SECCM-IRM): tracking phase formation on surfaces in small volumes

“…These data show that the intensity decreases over time after the feature appears on the image, indicating that the feature is growing in size with time, alongside the electrode plane. 31,32,61 Furthermore, by integrating the current over the cyclic voltammogram, one obtains the charge flowing through the ITO. The variation of the ROI intensity profile is remarkably similar to the morphology of the charge-time transient in Figure 3c.…”

“…The optical detection principle has been detailed in previous works. 28,31,32 It is based on the reflection of the light wave at the ITO-electrolyte interface and its possible interference with light wave scattered by objects present on the ITO surface, which disturb the local optical conditions and are highlighted within the background, with the camera acting as an interferometric detector. Optical features can show either a negative contrast, the feature appearing darker than the background, or a positive contrast, where the feature appears brighter than the background.…”

“…[28][29][30] As a surface sensitive technique, IRM is particularly suited to the investigation of phenomena at the electrode/electrolyte interface. [31][32][33][34] At optically transparent electrodes, such as indium tin oxide (ITO) immersed in solution, local phase formation and/or change at the electrode surface modify the refractive index, giving rise to a difference in contrast in the observed reflected light image. For example, this phase change can arise from the growth of nanoparticles or crystals at the electrode surface providing real-time in situ observation of the phase formation event.…”

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

“…This difference of behavior is most likely due to the surface heterogeneities of the ITO surface that affect its electroactivity. [30] According to Moffat et al, [9,10] the reduction peak in Figure 2 a1 ( % 70 % incidence from 20 LSVs), is related to Ni 2+ reduction and deposition of a Ni film. However it is also concomitant to water reduction resulting in the precipitation of a Ni(OH) 2 layer, which is a better catalyst than bare Ni [31,32] for water reduction, until it completely blocks further charge transfer.…”

“…To capture the reported diversity in electrochemical signatures, we leverage the capability of scanning electrochemical cell microscopy, SECCM, [28] to screen, electrochemically, at high throughput multiple areas of an electrode. Coupling SECCM to a correlated optical microscopy monitoring, [29,30] grants a complementary screening of the behavior of these different areas, here through the super-localization identification of many individual NPs. This is performed by confining a droplet of a 1 to 5 mM NiCl 2 + 0.1 M KCl electrolyte on the ITO with the tip end of a micropipette, and imaging this microelectrochemical cell during linear sweep voltammetry (LSV), in reflection mode, by IRM.…”