WEB Ultrasonic-plasma engineering of single-atom doped carbon as bi-functional oxygen electrocatalysts: From experimental to theoretical theoryThursday (24.09.2020) 09:00 - 09:15 M: Modelling and Simulation 1 Part of:
Bi-functional oxygen electrocatalysts is essential for sustainable green energy systems, including fuel cell, water electrolysis, and metal-air batteries. However, the main challenges in high overpotential, low energy efficiency and active sites in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) limiting its widespread commercialization. The state-of-the art noble electrocatalysts (such as Pt, Ru or Ir) have high cost as well as poor stability in charge-discharge process. Among various noble-metal-free electrocatalysts, isolated transitional metal (TM) single-atom within nitrogen-doped carbon matrix, denoted as TM-N-C, were considered as the most promising materials to substitute noble-metal catalysts with excellent ORR and OER activity owing to the almost~ 100% utilization efficiency and surface active energy. Herein, we demonstrate a novel synthesize route of isolated M-N-C catalysts via ultrasonic-plasma engineering. The in situ ultrasonic generation during room-temperature plamsa synthesis process can successfully avoid the agglomeration of metal ions, and thus can realize single-atom doped carbon. The atomically dispersed TM-N-C) catalyst showed superior ORR and OER activity and stability compared to most of other reported electrocatalysts and the commercial Pt/C and Ir/C catalyst in an alkaline medium. In particular, a notable outstanding potential difference ΔE (ΔE = Ej=10 - E1/2) of Fe-N-C or Co-N-C as low as 0.80-0.83 V, which outperformed the benchmark Pt-Ir/C catalysts with same catalyst loading (ΔE = 0.85 V). In a home-made Zn-air rechargeable battery, both Fe-N-C or Co-N-C as the air electrode catalysts exhibited higher power density, specific capacity and lower overpotential over 100 charge-discharge cycles than that of Pt-Ir/C electrocatalysts. DFT calculation also supported that Co and Fe as single-atom matrix has the most balanced ORR and OER mechanism among the various TM-N-C catalysts.