A Comparative Study of Functionalized High-Purity Carbon Nanotubes towards the V(IV)/V(V) Redox Reaction Using Cyclic Voltammetry and Scanning Electrochemical Microscopy

作者：Steimecke Matthias; Ruemmler Stefan; Schuhmacher Nils Frederik; Lindenberg Titus; Hartmann Mark; Bron Michael^*

来源：Electroanalysis, 2017, 29(4): 1056-1061.

DOI：10.1002/elan.201600614

• all-vanadium redox flow battery
• cyclic voltammetry
• scanning electrochemical microscopy
• carbon nanotubes
• functionalization

Functionalized high purity carbon nanotubes (CNTs) with various amounts of oxygen containing surface groups were investigated towards the relevant redox reactions of the all-vanadium redox flow battery. The quinone/hydroquinone redox peaks between 0.0 and 0.7V vs. Ag|AgCl|KClsat. were used to quantifying the degree of functionalization and correlated to XPS results. Cyclic voltammetry in vanadyl sulfate-containing 3M H2SO4 as a common supporting electrolyte showed no influence of the amount of surface groups on the V(IV)/V(V) redox system. In contrast, the reactions occurring at the negative electrode (V(II)/V(III) and V(III)/V(IV)) are strongly affected by oxygen surface groups. However, under modified experimental conditions, SECM experiments detecting the consumption of VO2+ molecules by CNT thin films in pH=2 solution show improved onset potentials with increased surface oxygen content up to approximate to 3 at%. Further increase in surface oxygen up to 8 at% led to minor improvement. These dissimilar results under different experimental conditions are rationalized by suggesting that oxygen functional groups do not form the active site for the V(IV)/V(V) reaction but wetting of the catalyst layer is of high importance.

• 出版日期2017-4