In-operando 3D visualization of nickel electrodeposition and mass transport phenomena: Insights from X-ray microcomputed tomography

Nickel electrodeposition is widely used in industrial applications due to its ability to enhance the mechanical and corrosion resistance of metallic substrates. However, understanding mass transport mechanisms during electrodeposition remains a challenge, as conventional models struggle to describe complex three-dimensional phenomena such as concentration gradients, depletion zones, and convective instabilities. In this study, we employ X-ray micro-computed tomography (X-ray µCT) in-operando imaging technique to investigate the electrodeposition of nickel on titanium under potentiostatic conditions. Chronoamperometric analysis and scanning electron microscopy (SEM) confirmed distinct deposition behaviors at −0.5 V and −1.2 V, with negligible deposition at the lower potential and significant nickel growth, including dendritic structures, at the higher potential. The X-ray µCT images revealed the formation of structured ionic layers near the electrode surfaces, with Ni²⁺ ion migration and concentration gradients influencing deposition dynamics. At −1.2 V, depletion zones and convective instabilities were identified, suggesting a competition between diffusion, migration, and Rayleigh-Bénard convection. These findings demonstrate the feasibility of X-ray µCT for real-time 3D visualization of electrochemical processes, providing novel insights into mass transport during electrodeposition.