Understanding the Growth of Electrodeposited PtNi Nanoparticle Films Using Correlated <i>In Situ</i> Liquid Cell Transmission Electron Microscopy and Synchrotron Radiation

Electrodeposition is a versatile method for synthesizing nanostructured films, but controlling the morphology of films containing two or more elements requires a detailed understanding of the deposition process. We used liquid cell transmission electron microscopy to follow the electrodeposition of PtNi nanoparticle films on a carbon electrode during cyclic voltammetry. These <i>in situ</i> observations show that the film thickness increases with each cycle, and by the fourth cycle, branched and porous structures could be deposited. Synchrotron studies using <i>in situ</i> transmission X-ray microscopy further revealed that Ni was deposited in the oxide phase. <i>Ex situ</i> studies of bulk electrodeposited PtNi nanoparticle films indicated the number of cycles and the scanning rate were the most influential parameters, resulting in a different thickness, a different homogeneity, a different nanoparticle size, and a different surface structure, while the precursor concentration did not have a significant influence. By varying the potential range, we were able to obtain films with different elemental compositions.