Abstract
In this work, we demonstrate electrochemical methods for determination of porosity and surface area of thin films of interconnected nickel nanowires. While the standard porosimetry and gas adsorption methods lack sensitivity for characterization of thin metallic films, the electrochemical methods employing coulometry, cyclic voltammetry and electrochemical impedance spectroscopy can be applied to accurately determine textural properties of micron- and sub-micron thick nanostructured materials. Additionally, in this work we evaluated accuracy and precision of five electrochemical signals recorded during cyclic voltammetry and electrochemical impedance spectroscopy, which are commonly used for determination of electrochemical surface area (AECSA) of various nickel electrodes. By verifying the data with two independent surface characterization techniques, we found that the analysis based on surface-limited oxidation of nickel and on capacitive charging of nickel surface during hydrogen evolution reaction give the best accuracy and smallest errors. We also show that experimental conditions play a crucial role in the accurate determination of AECSA of nickel nanomaterials. If the influence of experimental conditions is not corrected for, the electrochemical surface area can differ by over 250% compared to the surface area determined with other methods.
Highlights
Extended surface area nickel materials, such as macroporous foams or micro- and mesoporous sponges, are broadly used in multiple applications, for example catalysis,[1,2] sensing,[3] water electrolysis[4,5] or energy storage.[6]
In this work we used a combination of electrochemical techniques to characterize thin films of nickel nanowire meshes for their porosity and surface area
The porosity of the nanoporous material was determined by analysing the thickness of the nanomesh and the electric charge spent during its electrodeposition
Summary
Extended surface area nickel materials, such as macroporous foams or micro- and mesoporous sponges, are broadly used in multiple applications, for example catalysis,[1,2] sensing,[3] water electrolysis[4,5] or energy storage.[6]. In the study of macroporous nickel foams, Grdeń et al obtained similar AECSA values from the CV and (partially dependent) EIS measurements using common reference values of nickel oxidation charge and double layer capacitance,[40] our attempts to use their approach for characterization of thin films of nanoporous nickel yielded very inaccurate results In this contribution we present detailed methodology we developed for exact determination of porosity and surface area of the few-micron thick nickel nanomesh. The 95% confidence limits of the simulated values were estimated with the total derivative method
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