3D Honeycomb Nanostructure Comprised of Mesoporous N-Doped Carbon Nanosheets Encapsulating Isolated Cobalt and Vanadium Nitride Nanoparticles as a Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction

The development of high-efficiency non-noble metal catalysts for the oxygen reduction reaction (ORR) is of paramount significance to sustainable energy-conversion technologies. Herein, a three-dimensional (3D) honeycomb nanostructure comprised of mesoporous N-doped carbon nanosheets encapsulating isolated cobalt and vanadium nitride nanoparticles (denoted Co-VN-NC) is synthesized through a facile one-step pyrolysis method. The catalyst prepared under optimal temperature exhibits excellent ORR performance with an E-onset of 0.032 V and an E-1/2 of -0.086 V (vs Ag/AgCl) in 0.1 M KOH solution, which is very close to that of commercial 20% Pt/C, and it also shows better ORR performance in 0.5 M H2SO4 solution. Moreover, it demonstrates a superior enhanced tolerance to methanol poisoning compared with that of Pt/C. More importantly, the optimized catalyst shows extraordinary stability with a little current decline of less than 4 and 8% during chronoamperometric evaluation for more than 30 000 s in alkaline and acidic solutions, respectively. It has been proved that the catalyst favors an efficient four-electron pathway-dominated ORR process. The excellent performance can be ascribed to the 3D honeycomb nanostructure with a number of mesopores, which possesses high specific surface area (433.20 m(2) g(-1)) conducive to the high exposure level of the active sites, the efficient electron-transfer capability between different metal nanoparticles, and a powerful protective effect of the N-doped carbon layer. This work not only provides great potential non-noble metal ORR electrocatalysts comparable to Pt/C but also puts forward a simple and scalable pyrolysis method to prepare nonprecious metal catalysts.