This journal is c The Royal Society of Chemistry 2011 Chem. Commun., 2011, 47, 4463–4465 4463 Cite this: Chem. Commun., 2011, 47, 4463–4465 Efficient electrocatalytic oxygen reduction over metal free-nitrogen doped carbon nanocapsulesw Sangaraju Shanmugam* and Tetsuya Osaka* Received 19th January 2011, Accepted 17th February 2011 DOI: 10.1039/c1cc10361j Nitrogen doped carbon nanocapsules (NCNCs) were synthesized as a non-noble electrocatalyst for the ORR using a simple and efficient route. The NCNCs exhibited higher activity than the commercial Pt/C catalyst, excellent stability, and resistance to methanol oxidation in the oxygen reduction reaction. The synthesis of a low cost and high performance catalyst for the oxygen reduction is one of the most critical challenges for the successful development of fuel cells for portable and transportation applications. 1 Platinum or its alloys dispersed on the carbon is the most effective for oxygen reduction reaction. 2 However, the sluggish oxygen reduction and high cost, low abundance of Pt based electrocatalysts are the most technical limitations in the commercialization of fuel cell technology. Research efforts have been focused to decrease the cost of Pt electrocatalysts by two approaches (i) reducing the Pt loading and (ii) to explore non-precious catalysts. Recently, nitrogen doped carbon nanomaterials have received enormous importance as non-precious electrode materials for oxygen reduction. 3 Generally, the nitrogen doping in carbon nanostructures has been carried out by in situ doping during the synthesis or through post-treatment (postdoping) of pre-formed carbon nanostructures. 4 In the latter method, the carbon material is subjected to heat treatment in a nitrogen containing atmo- sphere (NH 3 plasma, N-ion implantation, etc.). The in situ nitrogen doping in CNTs or CNFs is generally achieved by thermal decomposition of nitrogen containing hydrocarbons over metal catalyst particles such as Fe, Co, Ni and Cu by using arc-discharge, laser ablation, or chemical vapor deposition (CVD). 5 High energy consumption, expensive hardware and multistep processes of these techniques are mostly responsible for high cost of manufacturing nitrogen doped carbon nano- structures and thus limit their practical applications. We introduce a simple and an alternative route for the fabri- cation of nitrogen doped carbon nanocapsules. This was achieved by using one dimensional nanostructures as a sacrificial template and the template was synthesized by a straightforward single step route using a single component precursor. The method is facile, solvent-, catalyst-, and template-free and it is easy to handle. The novelty of the current approach relies on the synthesis of Gd 2 O 3 or Gd 2 O 2 CO 3 filled nitrogen doped carbon nanocapsules and we further demonstrate the use of these nanostructures as a versatile sacrificial template to prepare nitrogen doped carbon nanocapsules. Subsequently, the NCNCs were used as an electrocatalyst for the oxygen reduction reaction (ORR) and it was found that they exhibit superior activity and stability compared to a commercial electrocatalyst (Scheme 1). The solid state pyrolysis of gadolinium(III) diethylene triamine- pentaacetate at 700 and 900 1C under autogenic pressure resulted in Gd 2 O 2 CO 3 and Gd 2 O 3 filled carbon nanocapsules, respectively (Fig. S1, ESIw). The products were treated with concentrated HCl to dissolve oxide and the carbons derived from Gd 2 O 2 CO 3 @C and Gd 2 O 3 @C are denoted as NCNC 700 and NCNC 900 . Details of synthesis and characterization of Gd oxide filled carbon nanostructures are given in the ESI.w The electron microscopic (SEM and TEM) studies reveal that the products obtained at 700 and 900 1C show the presence of rod and capsule-like morphologies with uniform carbon coating and the diameter of the rod is in the range of 80–100 nm with few hundreds of nanometres length (Fig. S2, ESIw). The EDX spot analysis revealed that the core comprised of only Gd, O, C elements and C, N, O are observed in the shell (Fig. S3, ESIw). The SEM and TEM images of NCNCs are shown in Fig. 1a–d. The images show capsule-like morphology and are stacked together. Most of the NCNCs are free from the oxide core. The TEM image of NCNCs shows that the capsule is comprised of an outer diameter of about 80–120 nm and an inner diameter of about 25–50 nm. The carbon capsule Scheme 1 Schematic representation of the fabrication of nitrogen doped carbon nanocapsules by (i) formation of metal oxide filled nitrogen doped carbon, (ii) core removal. School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan. E-mail: sangarajus@aoni.waseda.jp, osakatets@waseda.jp w Electronic supplementary information (ESI) available: Details of synthesis and characterization of templates and XRD, EDX spectra and RDE traces of NCNCs. See DOI: 10.1039/c1cc10361j ChemComm Dynamic Article Links www.rsc.org/chemcomm COMMUNICATION Downloaded by Waseda University on 29 March 2011 Published on 08 March 2011 on http://pubs.rsc.org | doi:10.1039/C1CC10361J View Online