Boosted Oxygen Kinetics of Hierarchically Mesoporous Mo₂C/C for High‐current‐density Zn–air Battery

Abstract The high‐current‐density Zn–air battery shows big prospects in next‐generation energy technologies, while sluggish O₂ reaction and diffusion kinetics barricade the applications. Herein, the sequential assembly is innovatively demonstrated for hierarchically mesoporous molybdenum carbides/carbon microspheres with a tunable thickness of mesoporous carbon layers (Meso‐Mo₂C/C‐x, where x represents the thickness). The optimum Meso‐Mo₂C/C‐14 composites (≈2 µm in diameter) are composed of mesoporous nanosheets (≈38 nm in thickness), which possess bilateral mesoporous carbon layers (≈14 nm in thickness), inner Mo₂C/C layers (≈8 nm in thickness) with orthorhombic Mo₂C nanoparticles (≈2 nm in diameter), a high surface area of ≈426 m² g⁻¹, and open mesopores (≈6.9 nm in size). Experiments and calculations corroborate the hierarchically mesoporous Mo₂C/C can enhance hydrophilicity for supplying sufficient O₂, accelerate oxygen reduction kinetics by highly‐active Mo₂C and N‐doped carbon sites, and facilitate O₂ diffusion kinetics over hierarchically mesopores. Therefore, Meso‐Mo₂C/C‐14 outputs a high half‐wave potential (0.88 V vs RHE) with a low Tafel slope (51 mV dec⁻¹) for oxygen reduction. More significantly, the Zn–air battery delivers an ultrahigh power density (272 mW cm⁻²), and an unprecedented 100 h stability at a high‐current‐density condition (100 mA cm⁻²), which is one of the best performances.