Directly anchoring Fe3C nanoclusters and FeNx sites in ordered mesoporous nitrogen-doped graphitic carbons to boost electrocatalytic oxygen reduction

Porous carbon materials doped with nano-sized transition metal carbides and/or metal-nitrogen coordinative sites are promising oxygen reduction electrocatalysts. The doping of such functionalities in carbon materials with desirable concentration, ultra-small size and stable configuration is still a challenge. In this paper, by grinding and pyrolyzing solid mixtures of an amino acid, an iron salt, and a mesoporous silica template, we demonstrate a solvent-free assembly approach to directly anchor both Fe3C nanoclucters and FeNx sites into nitrogen-doped ordered mesoporous graphitic carbon materials. The carbonaceous electrocatalysts are imparted with several fascinating features, namely, highly dispersed ultra-small Fe3C nanoclusters of 1-3 nm, well-anchored FeNx sites, nitrogen-doped well-graphitized carbon frameworks, and ordered mesopores (similar to 5.4 nm) and high surface areas (>1000 m(2)/g), respectively. The combination of these features makes these electrocatalysts exceptional for oxygen reduction reaction under both alkaline and acidic electrolytes, i.e. superior catalytic activities (e.g. onset and half-wave potentials up to 1.00 and 0.89 V vs. the reversible hydrogen electrode in alkaline solution), outstanding stabilities and excellent methanol tolerance, respectively. An in-depth study has been conducted to identify and characterize the key active sites in these electrocatalysts and to elucidate several important influencing factors to optimize the catalytic performance. (C) 2017 Elsevier Ltd. All rights reserved.