MnCo2O4 Anchored on Nitrogen-Doped Carbon Nanomaterials as an Efficient Electrocatalyst for Oxygen Reduction

The hybrids composed of N-doped carbon (N-C) and transition-metal-based nanoparticles have attracted tremendous interest due to their outstanding catalytic performance for oxygen reduction reaction (ORR). Herein, we first synthesize a N-C nanomaterial by pyrolyzing the mesoporous-silica-protected zeolitic imidazolate framework-8 (ZIF-8). The synthesis involves formation of ZIF-8@SiO2 core-shell structure, thermal annealing in Ar and acid etching. Then, the MnCo2O4 nanoparticles are supported on the as-synthesized N-C via a facile solvothermal method. The obtained hybrid of MnCo2O4 and N-C (MnCo2O4/N-C) exhibits better ORR activity than other as-prepared contrast materials in terms of more positive half-wave potential and larger diffusion-limiting current density, close to the commercial Pt/C. Moreover, the MnCo2O4/N-C catalyst also shows better methanol tolerance and better operational stability than the benchmark Pt/C catalyst. The superior performance of MnCo2O4/N-C is attributed to its porous structure and large BET surface area, N-doping effect, small size MnCo2O4 nanoparticles loaded on the porous N-C and synergistic effects between the doped active species. Therefore, it is expected to replace Pt/C as a promising fuel cell catalyst in alkaline direct methanol fuel cells.