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

Abstract

AbstractThe 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.