Prussian blue and Prussian white thin-film electrodes: Single-step electrodeposition for anode and cathode applications

Abstract

This study examines how deposition potential influences the composition and nanoscale structure of Prussian Blue (PB)/Prussian White (PW)-family films, providing an experimental basis for assessing their proposed functions. Films were grown directly on Au/Cr/Si in a single potentiostatic step from a common aqueous bath at $-0.20$ to $+0.40$\,V versus a saturated calomel electrode, with a fixed deposition charge of 10\,mC. Electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy revealed potential-dependent chemistry and nonmonotonic morphology. EDS indicated greater K incorporation in lower-potential deposits, whose Fe~2p and Raman features were consistent with more reduced, PW-like environments. Surface K/Fe ratios varied nonmonotonically from 1.129 to 1.322 across the series, corresponding to 52.95--56.94\% K within the detected K+Fe population. Larger faceted crystallites at $+0.30$\,V contrasted with finer pyramids and cracks at $+0.40$\,V. Selected PB-like and PW-like regions had local cubic lattice parameters of $(10.31\pm0.10)$\,Å and $(10.36\pm0.10)$\,Å, respectively; their overlapping uncertainties prevent discrimination by lattice spacing alone. Cross-sectional maps showed broadly uniform framework-element distributions within locally continuous coatings. Together, these observations relate deposition conditions to contrasting chemical and morphological starting states without establishing bulk stoichiometry or phase purity. A literature-grounded outlook identifies ion storage, sensing, electrochromism, resistive switching, and ion handling as research opportunities requiring functional validation in these films.