Microwave-Assisted Synthesis of Co-Coordinated Hollow Mesoporous Carbon Cubes for Oxygen Reduction Reactions

Transition-metal-/metal-oxide-loaded mesoporous carbon materials with hollow structures are thought to have great potential as catalysts, especially in the areas of sustainable chemistry and energy conversion. However, it is hard to load transition metals/metal oxides onto carbon materials while keeping the carbon materials unchanged through traditional after-treatment processes, thus making it difficult to determine the true roles of the transition metal/metal oxide and carbon in the reactions. Here, Co-coordinated hollow mesoporous carbon cubes (CoMHMCCs) were prepared by a microwave-assisted approach in the presence of ethylene glycol and hollow mesoporous carbon cubes (HMCCs). The synthesized CoMHMCCs inherited most advantages of the HMCCs, such as large surface area and pore volume, uniform pore size distribution, and hollow mesoporous structure, and the Co species was found to coordinate with the N atoms in the N-doped hollow mesoporous carbon cubes. The synthesized CoMHMCCs exhibited a much enhanced oxygen electroreduction reaction activity (∼50 mV deviation from Pt/C), a high selectivity (number of electrons transferred = 3.7-3.9), and excellent electrochemical stability (as low as 12 mV negative shift of half-wave potential after 5000 potential cycles) as a result of a synergetic catalytic effect.