N- and F-Co-Doped Carbon Quantum Dots Coated on a Ni Foam Substrate as Current Collector for Highly Stable Li-Air Batteries

Abstract

Because of their high theoretical density, Li-air batteries (LABs) are expected to be critical components of future energy storage devices. However, the commercial use of LABs is limited by their low charge-discharge efficiency, high overpotential, and low cyclic stability. Therefore, to improve the cyclic stability of LABs, we manufactured N- and F-co-doped carbon quantum dots (NF-CQDs), thinly coated them on the surface of a Ni foam current collector via ultrasonic spray coating, and used the as-fabricated NF-CQD/Ni as the current collector of an LAB cathode. The NF-CQD/Ni-based cathode maintained remarkable cycling stability over 42 cycles (with a limited capacity was 1000 mAh/g) and exhibited a superior specific discharge capacity of approximately 5121.91 mAh/g (at 100 mA/g). NF-CQD/Ni-based cathode exhibits superior electrochemical properties, including its high cycling stability and high discharge capacity, primarily contributed by the NF-CQD coating layer, which prevented the oxidation of the Ni foam substrate and increased the electrical conductivity and electrocatalytic activity of the cathode. Therefore, NF-CQD/Ni can serve as an excellent current collector for LAB cathodes.

MOF-Derived Co Nanoparticles Catalyst Assisted by F- and N-Doped Carbon Quantum Dots for Oxygen Reduction

“…The N 1s XPS profiles showed the peaks of graphitic N (~400.80 eV), pyrrolic N (~399.99 eV), Co-N (~399.09 eV), and pyridinic N (~397.35 eV) (Figure 5b). Via the aromatic system, pyridinic N supplies two p-electrons, whereas pyrrolic-N provides one p-electron, thus resulting in increased catalytic activity [44,45]. Two core-level signal peaks at ~781.84 eV and ~797.50 eV were visible in the XPS spectrum of Co 2p (Figure 5d), corresponded to Co 2p3/2 and Co 2p1/2, and minor peaks of the Co 2+ satellite (~802.67, ~786.86 eV), and Co-N (~779.31 eV) Furthermore, only Co/FN-C showed two peaks at ~684.6 and ~687.6eV in the F 1s XPS spectra, which represent the semi-ionic and covalent bonds of C-F, owing to the F atoms in the FNCQDs (Figure 5c).…”