Nitrogen-Doped Hierarchical Porous Carbon Architecture Incorporated with Cobalt Nanoparticles and Carbon Nanotubes as Efficient Electrocatalyst for Oxygen Reduction Reaction

Hierarchical porous carbon has attracted great interest because of its distinctive structure and superior properties for designing electrochemical energy storage and conversion devices. In this work, a novel method to fabricate nitrogen-doped hierarchical porous carbon (NHPC) is reported, which is incorporated with Co nanoparticles and carbon nanotubes (CNTs). The NHPC is prepared using a facile and scalable MgO-Co template method. Metal nitrate-glycine solution combustion synthesis, followed by a high temperature calcination, is used to prepare MgO-Co/N-doped carbon precursor. CNTs are formed by the in situ Co-catalytic growth during heat treatment; at the same time, localized graphitic layers are also formed around the Co nanoparticles. After acid washing, NHPC with hierarchical multipores and ultrafine Co nanoparticles is obtained. When applied as oxygen reduction reaction (ORR) catalyst, the NHPC displays high catalytic activity not only in terms of onset potential and current density, but also superior durability and tolerance to methanol crossover in alkaline electrolyte. The remarkable ORR activity is originated from the cooperative effects of high specific surface area, hierarchical pore structure, ultrasmall Co nanocrystals, localized graphitic layers, CNTs, and N-doping.