4 research outputs found
FeNC catalysts decorated with NiFe<sub>2</sub>O<sub>4</sub> to enhance bifunctional activity for ZnāAir batteries
Rechargeable Znāair battery is a promising next-generation energy storage device attributed to its high energy density, excellent safety, and low cost. However, its commercialization is hampered by sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air electrodes. Herein, we have designed, fabricated, and demonstrated a highly efficient ORR/OER electrocatalyst, NiFe2O4/FeNC, using low-cost materials via a facile synthesis route. NiFe2O4 is successfully loaded on Fe/N-doped carbon (FeNC) through bonding to Fe3C in FeNC. Due to the existence of high ORR active sites such as FeN4 and Fe and N-doped carbon moieties, the half-wave potential of the ORR reaches a high value of 0.83 V. While benefited from NiFe2O4 with high OER activity and the synergistic effect between NiFe2O4 and FeNC, the overpotential is 310 mV at 10 mA cmā2 in the OER. The voltage difference between chargingādischarging operations in the Znāair battery employing the NiFe2O4/FeNC electrocatalyst only increases by 0.16 V after cycling for 100 h (600 cycles) at 10 mA cmā2, which is much lower than 1.28 V using the best commercial Pt/C and RuO2 catalysts.Ā </p
Supplementary information files for FeNC catalysts decorated with NiFe2O4 to enhance bifunctional activity for ZnāAir batteries
Supplementary files for article FeNC catalysts decorated with NiFe2O4 to enhance bifunctional activity for ZnāAir batteriesĀ
Rechargeable Znāair battery is a promising next-generation energy storage device attributed to its high energy density, excellent safety, and low cost. However, its commercialization is hampered by sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air electrodes. Herein, we have designed, fabricated, and demonstrated a highly efficient ORR/OER electrocatalyst, NiFe2O4/FeNC, using low-cost materials via a facile synthesis route. NiFe2O4 is successfully loaded on Fe/N-doped carbon (FeNC) through bonding to Fe3C in FeNC. Due to the existence of high ORR active sites such as FeN4 and Fe and N-doped carbon moieties, the half-wave potential of the ORR reaches a high value of 0.83 V. While benefited from NiFe2O4 with high OER activity and the synergistic effect between NiFe2O4 and FeNC, the overpotential is 310 mV at 10 mA cmā2 in the OER. The voltage difference between chargingādischarging operations in the Znāair battery employing the NiFe2O4/FeNC electrocatalyst only increases by 0.16 V after cycling for 100 h (600 cycles) at 10 mA cmā2, which is much lower than 1.28 V using the best commercial Pt/C and RuO2 catalysts.Ā Ā </p
Hierarchically Bicontinuous Porous Copper as Advanced 3D Skeleton for Stable Lithium Storage
Rechargeable
lithium metal anodes (LMAs) with
long cycling life have been regarded as the āHoly Grailā
for high-energy-density lithium metal secondary batteries. The skeleton
plays an important role in determining the performance of LMAs. Commercially
available copper foam (CF) is not normally regarded as a suitable
skeleton for stable lithium storage owing to its relatively inappropriate
large pore size and relatively low specific surface area. Herein,
for the first time, we revisit CF and address these issues by rationally
designing a highly porous copper (HPC) architecture grown on CF substrates
(HPC/CF) as a three-dimensional (3D) hierarchically bicontinuous porous
skeleton through a novel approach combining the self-assembly of polystyrene
microspheres, electrodeposition of copper, and a thermal annealing
treatment. Compared to the CF skeleton, the HPC/CF skeleton exhibits
a significantly improved Li plating/stripping behavior with high Coulombic
efficiency (CE) and superior Li dendrite growth suppression. The 3D
HPC/CF-based LMAs can run for 620 h without short-circuiting in a
symmetric Li/Li@Cu cell at 0.5 mA cm<sup>ā2</sup>, and the
Li@Cu/LiFePO<sub>4</sub> full cell exhibits a high reversible capacity
of 115 mAh g<sup>ā1</sup> with a high CE of 99.7% at 2 C for
500 cycles. These results demonstrate the effectiveness of the design
strategy of 3D hierarchically bicontinuous porous skeletons for developing
stable and safe LMAs
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 ZnāAir 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
metalāair 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 Znāair 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>ā1</sup> at 10 mA cm<sup>ā2</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 ā3.35 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 ā1.17
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 metalāair batteries