1 research outputs found
Mn<sub>3</sub>O<sub>4</sub> Quantum Dots Supported on Nitrogen-Doped Partially Exfoliated Multiwall Carbon Nanotubes as Oxygen Reduction Electrocatalysts for High-Performance Zn–Air Batteries
Highly
efficient and low-cost nonprecious
metal electrocatalysts that favor a four-electron pathway for the
oxygen reduction reaction (ORR) are essential for high-performance
metal–air batteries. Herein, we show an ultrasonication-assisted
synthesis method to prepare Mn<sub>3</sub>O<sub>4</sub> quantum dots
(QDs, ca. 2 nm) anchored on nitrogen-doped partially exfoliated multiwall
carbon nanotubes (Mn<sub>3</sub>O<sub>4</sub> QDs/N-p-MCNTs) as a
high-performance ORR catalyst. The Mn<sub>3</sub>O<sub>4</sub> QDs/N-p-MCNTs
facilitated the four-electron pathway for the ORR and exhibited sufficient
catalytic activity with an onset potential of 0.850 V (vs reversible
hydrogen electrode), which is only 38 mV less positive than that of
Pt/C (0.888 V). In addition, the Mn<sub>3</sub>O<sub>4</sub> QDs/N-p-MCNTs
demonstrated superior stability than Pt/C in alkaline solutions. Furthermore,
a Zn–air battery using the Mn<sub>3</sub>O<sub>4</sub> QDs/N-p-MCNTs
cathode catalyst successfully generated a specific capacity of 745
mA h g<sup>–1</sup> at 10 mA cm<sup>–2</sup> without
the loss of voltage after continuous discharging for 105 h. The superior
ORR activity of Mn<sub>3</sub>O<sub>4</sub> QDs/N-p-MCNTs can be ascribed
to the homogeneous Mn<sub>3</sub>O<sub>4</sub> QDs loaded onto the
N-doped carbon skeleton and the synergistic effects of Mn<sub>3</sub>O<sub>4</sub> QDs, nitrogen, and carbon nanotubes. The interface
binding energy of −3.35 eV calculated by the first-principles
density functional theory method illustrated the high stability of
the QD-anchored catalyst. The most stable adsorption structure of
O<sub>2</sub>, at the interface between Mn<sub>3</sub>O<sub>4</sub> QDs and the graphene layer, had the binding energy of −1.17
eV, greatly enhancing the ORR activity. In addition to the high ORR
activity and stability, the cost of production of Mn<sub>3</sub>O<sub>4</sub> QDs/N-p-MCNTs is low, which will broadly facilitate the real
application of metal–air batteries