Tuning Electrodeposition Parameters for Tailored Nanoparticle Size, Shape, and Morphology: An In Situ ec-STEM Investigation

Advances in vacuum-tight in situ liquid cell TEM systems have attracted significant attention because of the ability to directly interpret chemical and electrochemical reactions within their native liquid environments [1]. Conducting quantitative in situ electrochemistry experiments within the S/TEM is feasible using the relatively new platform of in situ electrochemical S/TEM (ec-S/TEM). In this approach, microfabricated electrochemical cells are used to seal the liquid electrolyte between two silicon microchips with electron transparent SiNx viewing membranes and micropatterned electrodes. The electrochemical microchip devices used in the present study have platinum reference and counter electrodes and a glassy-carbon working electrode (GC-WE) that are directly patterned on the microchip device. Figure 1a shows a schematic of the microfabricated electrochemical cell and vacuum-tight in situ TEM holder assembly. SEM images of the spacer microchip and electrochemical microchip are shown in Figure 1b and Figure 1c, respectively. The GC-WE is microfabricated onto the SiNx viewing window, which permits the direct visualization of electrochemical reactions occurring directly on the electron transparent glassy-carbon (Figure 1d). Quantitative electrochemical measurements can be performed using these small-scale electrochemical devices via techniques such as cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy, with no adverse effects from the electron beam [2]. In the present study, this method is used to investigate the dynamics of crystal nucleation and growth mechanisms. Moreover, we demonstrate how electrodeposition parameters (CV scan rate) can be adjusted to tailor the size-scale and morphology of electrodeposited nanoparticles.