What Determines the Electrochemical Properties of Nitrogenated Amorphous Carbon Thin Films?

Jarkko Etula, Niklas Wester, Touko Liljeström, Sami Sainio, Tommi Palomäki, Kai Arstila, Timo Sajavaara, Jari Koskinen, Miguel A. Caro, Tomi Laurila*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
8 Downloads (Pure)

Abstract

Linking structural and compositional features with the observed electrochemical performance is often ambiguous and sensitive to known and unknown impurities. Here an extensive experimental investigation augmented by computational analyses is linked to the electrochemical characterization of in situ nitrogen-doped tetrahedral amorphous carbon thin films (ta-C:N). Raman spectroscopy combined with X-ray reflectivity shows nitrogen disrupting the sp3 C-C structure of the reference ta-C, supported by the observations of graphitic nitrogen substitution in X-ray absorption spectroscopy. The surface roughness also increases, as observed in atomic force microscopy and atomic-level computational analyses. These changes are linked to significant increases in the hydrogen and oxygen content of the films by utilizing time-of-flight elastic recoil detection analysis. The conductivity of the films increases as a function of the nitrogen content, which is seen as a facile reversible outer-sphere redox reaction on ta-C:N electrodes. However, for the surface-sensitive inner-sphere redox (ISR) analytes, it is shown that the electrochemical response instead follows the oxygen and hydrogen content. We argue that the passivation of the required surface adsorption sites by hydrogen decreases the rates of all of the chemically different ISR probes investigated on nitrogenated surfaces significantly below that of the nitrogen-free reference sample. This hypothesis can be used to readily rationalize many of the contradictory electrochemical results reported in the literature.

Original languageEnglish
Pages (from-to)6813–6824
Number of pages12
JournalChemistry of Materials
Volume33
Issue number17
Early online date23 Aug 2021
DOIs
Publication statusPublished - 14 Sep 2021
MoE publication typeA1 Journal article-refereed

Fingerprint

Dive into the research topics of 'What Determines the Electrochemical Properties of Nitrogenated Amorphous Carbon Thin Films?'. Together they form a unique fingerprint.

Cite this