Nitrogen-Doped 3D Graphene-like Carbon Synthesized Using a Zeolite Template As a Metal-Free Oxygen Reduction Electrocatalyst

Abstract

Ordered microporous carbons synthesized using a zeolite template have gained much attention owing to their excellent performances in advanced energy applications, including oxygen reduction reaction, electrical double-layer capacitors, and batteries. Their outstanding performances were attributed to the physicochemical properties of the carbon, such as high surface area of >2000 m2 g-1, large pore volume of >1.0 cm3 g-1 , and high conductivity. The electronic properties of zeolite-templated carbon (ZTC) can be modified through doping with heteroatoms, which can result in a further improvement of its electrochemical activities. The synergistic combination of its structural features and modified electronic properties is expected to enhance the performance of carbon as an electrode material in electrochemical applications. In this regard, we synthesized nitrogen-doped ZTCs using various nitrogen-containing carbon precursors. The synthesis was done with an aid of Ca2+ ion catalysts embedded inside the zeolite framework, following the recently reported approach by our group. The precursors were selected considering the size of the precursor molecule, the strength of carbon-nitrogen bond, and their interactions with Ca2+ ion catalysts. The resultant carbon exhibited high nitrogen content, uniform microporosity, high surface area, and 3D pore structure. Herein, we report the characterization of nitrogen-doped ZTC, and performances of both nitrogen-doped and undoped ZTCs as a metal-free catalyst for oxygen reduction reaction, focusing on the oxygen reduction behavior according to the nitrogen content, nitrogen bonding configurations, and porous texture of the carbon.