Design of house centipede-like MoC-Mo2C nanorods grafted with N-doped carbon nanotubes as bifunctional catalysts for high-performance Li-O-2 batteries

Abstract

Developing effective bifunctional catalysts to promote Li2O2 oxidation and to realize high-performance Li-O-2 batteries with long cycle life is a key challenge. Herein, a house centipede-like bifunctional catalyst consisting of a molybdenum carbide nanorod grafted with N-doped carbon nanotubes (denoted as MoC-Mo2C/NCNTs) is developed for enhancing the performance of Li-O-2 batteries. This nanocatalyst is successfully fabricated by the post-treatment of MoO3 nanorods coated with a Co-based zeolitic imidazolate framework (ZIF-67). The obtained MoC-Mo2C/NCNT nanorods have a unique structure with a body comprising small MoC-Mo2C nanocrystals and Co@NCNTs extending like legs from it. This structural architecture not only provides numerous catalytic active sites and sufficient space for accommodating Li2O2 but also facilitates electron transport through the catalytically active NCNT conducive pathways. Consequently, the MoC-Mo2C/NCNTs show substantially improved electrocatalytic performance in Li-O-2 batteries with a significantly reduced discharge-charge overpotential (0.50 V), high specific discharge capacity (34,862 mA h g(-1) at 200 mA g(-1)), and long cycle stability (up to 162 cycles at current density of 200 mA g(-1)) and cut-off capacity of 500 mA h g(-1). Preliminary results suggest that the MoC-Mo2C/NCNT nanorod is an efficient, stable bifunctional catalyst for Li-O-2 batteries.