Mild oxidation regulating the surface of Mo2CTx MXene to enhance catalytic activity for low overpotential and long cycle life Li-CO2 batteries

The lithium-carbon dioxide (Li-CO2) batteries hold promise for energy storage, given their capacity to capture and convert carbon dioxide (CO2). However, the practical application of Li-CO2 batteries continues to face substantial obstacles caused by sluggish CO2 reduction/evolution kinetics, resulting in high overpotential and short lifespan. This work presents the fabrication of a highly effective MoO2@Mo2C heterostructure hybrid catalyst using a CO2 oxidation strategy. This strategy integrated (in-situ) MoO2 onto the surface of two-dimensional (2D) Mo2C MXene, enhancing catalytic activity while preserving 2D electron/ion pathways. As a result, the MoO2@Mo2C, when used as a catalyst in Li-CO2 battery showcased a discharge capacity of 20790.8 mAh/g at a current density of 200 mA g−1. Notably, it achieved a long cycling life of 230 cycles at a cutoff capacity of 1000 mAh/g with a voltage gap as low as 1.85 V, which was significantly superior to that of a pristine Mo2CTx catalyst (3.61 V after twenty cycles). This work provides critical insights into the design of MXenes-based high-performance catalysts for advanced Li-CO2 batteries.