Electrochemical vs. X-ray Spectroscopic Measurements of NiFe(CN)6 Crystals
Dr. Jennifer Hampton, Physics
Pseudocapacitive materials like hexacyanoferrate have greater energy storage capabilities than standard capacitors while maintaining an ability to charge and discharge quickly. By modifying the surface of an electrodeposited nickel thin film with a layer of hexacyanoferrate, we can enhance its electrochemical properties. Charging and discharging these modified films using cyclic voltammetry (CV) allows us to obtain a measurement of the electrochemically active iron in the film. To determine how closely this resembles the full amount of iron in the film, we measure the films’ composition using particle-induced x-ray emission (PIXE). We also vary the amount of nickel deposited, both to compare the electrolysis value of charge deposited to the PIXE measurement of nickel in the film, and also to measure how varying the thickness of the nickel surface to which hexacyanoferrate adheres affects the presence of iron in the film. Comparisons of the CV and PIXE measurements show agreement in nickel levels but disagreement in iron levels. PIXE measurements of iron in the film have positive correlation with nickel in the film, possibly because there is more nickel available to be incorporated into the hexacyanoferrate crystal lattice. This correlation between PIXE nickel and PIXE iron measurements suggests that PIXE provides a reliable measure of iron in the film. This in turn implies that a variable proportion of total iron in a given film is electrochemically active.
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