@article{Chen_Kim_Je_Choi_Shi_Vladimir_Kim_Li_2021, title={Ultrasonic Plasma Engineering Toward Facile Synthesis of Single-Atom M-N4/N-Doped Carbon (M = Fe, Co) as Superior Oxygen Electrocatalyst in Rechargeable Zinc–Air Batteries}, volume={13}, url={https://nmlett.org/index.php/nml/article/view/824}, DOI={10.1007/s40820-020-00581-4}, abstractNote={<p>As bifunctional oxygen evolution/reduction electrocatalysts, transition-metal-based single-atom-doped nitrogen–carbon (NC) matrices are promising successors of the corresponding noble-metal-based catalysts, offering the advantages of ultrahigh atom utilization efficiency and surface active energy. However, the fabrication of such matrices (e.g., well-dispersed single-atom-doped M-N<sub>4</sub>/NCs) often requires numerous steps and tedious processes. Herein, ultrasonic plasma engineering allows direct carbonization in a precursor solution containing metal phthalocyanine and aniline. When combining with the dispersion effect of ultrasonic waves, we successfully fabricated uniform single-atom M-N<sub>4</sub> (M = Fe, Co) carbon catalysts with a production rate as high as 10&nbsp;mg&nbsp;min<sup>−1</sup>. The Co-N<sub>4</sub>/NC presented a bifunctional potential drop of Δ<em>E</em> = 0.79&nbsp;V, outperforming the benchmark Pt/C-Ru/C catalyst (Δ<em>E</em> = 0.88&nbsp;V) at the same catalyst loading. Theoretical calculations revealed that Co-N<sub>4</sub> was the major active site with superior O<sub>2</sub> adsorption–desorption mechanisms. In a practical Zn–air battery test, the air electrode coated with Co-N<sub>4</sub>/NC exhibited a specific capacity (762.8&nbsp;mAh&nbsp;g<sup>−1</sup>) and power density (101.62&nbsp;mW&nbsp;cm<sup>−2</sup>), exceeding those of Pt/C-Ru/C (700.8&nbsp;mAh&nbsp;g<sup>−1</sup> and 89.16&nbsp;mW&nbsp;cm<sup>−2</sup>, respectively) at the same catalyst loading. Moreover, for Co-N<sub>4</sub>/NC, the potential difference increased from 1.16 to 1.47&nbsp;V after 100 charge–discharge cycles. The proposed innovative and scalable strategy was concluded to be well suited for the fabrication of single-atom-doped carbons as promising bifunctional oxygen evolution/reduction electrocatalysts for metal–air batteries.</p> <p>Highlights:</p> <p>1 Single-atom M-N<sub>4</sub>/N-doped carbons (M = Fe, Co) prepared as OER/ORR catalysts.<br>2 Ultrasonication-assisted plasma engineering used for catalyst synthesis.<br>3 Co-N<sub>4</sub>/NC outperformed benchmark commercial catalysts in practical Zn–air battery test.<br>4 DFT calculations provided insights into the origin of superior ORR/OER performance.</p>}, journal={Nano-Micro Letters}, author={Chen, Kai and Kim, Seonghee and Je, Minyeong and Choi, Heechae and Shi, Zhicong and Vladimir, Nikola and Kim, Kwang Ho and Li, Oi Lun}, year={2021}, month={Jan.}, pages={60} }