Electrochemical purification of carbon nanotube electrodes

We present a fast and effective electrochemical method to purify random networks of single-walled carbon nanotubes (SWCNTs) that leads to total removal of metal catalyst without apparent detrimental effect on the electrochemical properties of the electrodes. The efficiency of the electrochemical purification has been compared with that of conventional chemical purification (acid washing). The disappearance of the peaks corresponding to the electrochemical redox reactions of iron during electrochemical purification evidences removal of iron impurities. The efficiency of electrochemical cleaning is further corroborated by cyclic voltammetry (CV) of an iron-sensitive electrochemical reaction, hydrazine oxidation. X-ray photoelectron spectroscopy also indicates that no iron can be detected after electrochemical purification whereas some iron is still left after acid washing. Moreover, Raman spectroscopy reveals higher degree of SWCNT damage after chemical purification compared to the electrochemical one. Electrochemically purified and pristine SWCNT electrodes exhibit similar conductivity, electrochemistry and performance as optically transparent electrodes for an iron-insensitive redox probe, Ru(bipy)³⁺⁼²⁺₃ .