Cyanamide derived thin film on carbon nanotubes as metal free oxygen reduction reaction electrocatalyst

Nitrogen-carbon complex coated carbon nanotubes were synthesized by a metal-free post treatment of commercial carbon nanotubes with cyanamide. Following a reflux and pyrolysis procedure, these materials were found to display increased oxygen reduction reaction (ORR) activity and selectivity towards an overall four electron reduction mechanism with increasing cyanamide loadings in alkaline electrolyte solution. The ORR activity was attributed to a thin surface layer remaining after pyrolysis, most likely containing pyridinic and quaternary nitrogen species acting as the active site structures. These materials also displayed considerable ORR activity in neutral conditions, with insight into the mechanistic pathway of oxygen reduction presented. This work demonstrates that the utilization of non-precious metal precursor species is not a stringent requirement for the formation of oxygen reduction active catalyst materials and presents a sustainable class of fuel cell electrocatalyst. (C) 2011 Elsevier Ltd. All rights reserved.