Analytical Sciences

Abstract − Analytical Sciences, 37(6), 865 (2021).

Suppression of Surface Oxygen on Nanocarbon Film Electrodes for Maintaining Electrode Activity
Mitsunobu TAKEMOTO,*,** Tomoyuki KAMATA,*** Motoki HAISHI,* Dai KATO,*** and Masahiko HARA**
*Nitto Denko Corporation, 1-1-2 Shimohozumi, Ibaraki, Osaka 567-8680, Japan
**School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8502, Japan
***Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
We investigated sputtered nanocarbon films with respect to the effect of suppressing surface oxygen on their electrochemical properties. The nanocarbon film consisted of nanocrystallites with mixed sp2 and sp3 bonds formed by unbalanced magnetron sputtering. Ultraviolet/ozone (UV/O3) irradiation and electrochemical pretreatment (ECP) were conducted to change the surface oxygen concentration of nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of the surface roughness (Ra) at the angstrom level after treatments, owing to a stable structure containing 40% of sp3 bonds. The electrode characteristics, including the potential window and electrochemical properties for some redox species, such as Ru(NH3)63+/2+, were investigated. Some electrochemical measurements of zinc ions (Zn2+) and hydrogen peroxide (H2O2) showed that the electrochemical reaction was improved by suppressing the surface oxygen. These results clearly indicated that the low surface oxygen concentration plays an important role in these electrochemical reactions.