Tailoring the electrocatalytic oxygen reduction reaction pathway by tuning the electronic states of single-walled carbon nanotubes

Carbon nanomaterials are emerging as a kind of promising electrocatalyst for oxygen reduction reaction (ORR) whether to produce hydrogen peroxide (H2O2) or to be applied in energy conversion devices. However, it is unexplored up to now whether the electronic states of carbon nanomaterials, such as single-walled carbon nanotube (SWNT), will affect its reaction pathway of ORR. Herein, we demonstrate that the selectivity towards H2O2 during ORR of SWNT can be controllably tailored by filling of a series of foreign substances, such as potassium (K), iron (Fe), fullerene (C60) and iodine (I2). This tunability is ascribed to the modification of electronic states of SWNT by electron transfer between SWNT and the filled species, as evidenced by Ultraviolet–visible–near infrared absorption spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the more negatively the carbon atoms are charged, the more preferentially the four electrons route is to undergo. Contrarily, the more positively the carbon atoms are charged, the more tendentiously the two electrons pathway is to conduct.