Synergistic Size and Electronic Engineering of Cr₃C₂@C(Nx) Nanoparticles Via Arc-Discharge for High-Performance...

Developing efficient non-precious oxygen reduction reaction (ORR) catalysts is essential for advancing zinc-air batteries (ZABs). This work presents a one-step synthesis of core-shell Cr₃C₂@C nanoparticles (NPs) via DC arc-discharge plasma. Precise regulation of cooling dynamics achieves a switch from growth-dominated to nucleation-dominated regimes, enabling controlled preparation of nanoparticles with distinct sizes. The liquid-nitrogen-cooled Cr₃C₂@C_ln NPs exhibit smaller size and higher surface area, leading to enhanced ORR performance. Subsequent nitrogen doping at 700 °C produces Cr₃C₂@C_ln(Nx) catalysts with precisely tuned nitrogen content (0.65-1.24 at.%). The optimized Cr₃C₂@C_ln(N_1.13) demonstrates outstanding ORR activity with a half-wave potential (E_1/2) of 0.81 V and superior kinetics, surpassing commercial Pt/C. In situ optical emission spectroscopy (OES) monitors the plasma state and electron temperature, providing fundamental insights into nucleation mechanisms. Density functional theory (DFT) calculations reveal that nitrogen doping optimizes the p-band center of carbon and significantly reduces the energy barrier of the rate-determining step (RDS) (*OH desorption). When applied in both liquid and solid-state flexible zinc-air batteries (FZABs), the Cr₃C₂@C_ln(N_1.13)-based cathode delivers exceptional performance, achieving high power densities (230.64 and 164.83 mW·cm^-2, respectively) and remarkable cycling stability. This study offers an efficient strategy for designing high-performance transition metal carbide electrocatalysts through synergistic control of size and electronic structure.