Boosted Oxygen Kinetics of Hierarchically Mesoporous Mo<sub>2</sub>C/C for High‐current‐density Zn–air Battery
Junye Zhang, Chenfeng Xia, Yaqiong Su, Lianhai Zu, Zaiwang Zhao, Peng Li, Zirui Lv, Jiazheng Wang, Bingbao Mei, Kun Lan, Tiancong Zhao, Pengfei Zhang, Weinan Chen, Shahid Zaman, Yi Liu, Liang Peng, Bao Yu Xia, Ahmed A. Elzatahry, Wei Li, Dongyuan Zhao
Abstract
Abstract The high‐current‐density Zn–air battery shows big prospects in next‐generation energy technologies, while sluggish O 2 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‐Mo 2 C/C‐x, where x represents the thickness). The optimum Meso‐Mo 2 C/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 Mo 2 C/C layers (≈8 nm in thickness) with orthorhombic Mo 2 C nanoparticles (≈2 nm in diameter), a high surface area of ≈426 m 2 g −1 , and open mesopores (≈6.9 nm in size). Experiments and calculations corroborate the hierarchically mesoporous Mo 2 C/C can enhance hydrophilicity for supplying sufficient O 2 , accelerate oxygen reduction kinetics by highly‐active Mo 2 C and N‐doped carbon sites, and facilitate O 2 diffusion kinetics over hierarchically mesopores. Therefore, Meso‐Mo 2 C/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.