Electrochemical TEM: Simulating Electrochemistry Coupled with Radiolysis

In situ electrochemical transmission electron microscopy (EC-TEM) offers unique opportunities to directly visualize electrochemical transformations at the nanoscale. However, reliable interpretation is hindered by the coupled effects of electrochemistry, electron-beam-induced radiolysis, and mass transport in confined electrolytes. Here, we combine nickel electrodeposition experiments with finite element simulations to disentangle these interactions. The model integrates Nernst–Planck ion transport, Navier–Stokes fluid dynamics, and radiolysis kinetics, enabling the systematic evaluation of beam effects under realistic EC-TEM conditions. First, we show that the flow direction and magnitude govern the spatial redistribution of reactive species, giving rise to anisotropic nanoparticle growth. We then show that radiolysis products strongly modulate the electrochemical current and hence the anisotropy of nanoparticle growth. Their impact depends on the electrolyte thickness, flow velocity, and applied overpotential. Thick electrolyte layers (≈μm), such as those occurring as a consequence of bulging, and low overpotentials favor radiolysis-driven bulk effects, whereas nanoscale electrolyte layers (≈100 nm) and high overpotentials minimize the contributions of radiolysis products, enhancing the interpretability of the electrochemical process during EC-TEM experiments. Importantly, simulations reveal parameter windows where oxidative and reductive radiolysis pathways compensate, resulting in radiolysis-neutralized conditions. These findings establish practical guidelines to minimize beam-induced artifacts and accurately interpret in situ EC-TEM measurements. This generalized framework is transferable to other metals, providing a robust strategy to design and analyze nanoscale electrochemical experiments using liquid-cell TEM.