Efficient Li–CO₂ Batteries with Molybdenum Disulfide Nanosheets on Carbon Nanotubes as a Catalyst

Molybdenum disulfide nanosheets (MoS2-NS) are employed as a bifunctional carbon dioxide (CO2) reduction and lithium carbonate (Li2CO3) decomposition catalyst in Li–CO2 batteries. Li–CO2 cells built with the prepared freestanding MoS2-NS–multiwalled carbon nanotube–single-walled carbon nanotube composite membrane as a CO2 gas diffusion cathode achieve 50 discharge/charge cycles with a low overpotential, i.e., with a discharge voltage >2.75 V and a charge voltage <3.75 V. In addition to improving cycling stability and efficiency, the MoS2 catalyst also improves discharge capacity by ∼50% and achieves full charge after full discharge. Successful reversibility of the carbon dioxide reduction reaction (CDRR) and carbon dioxide evolution reaction (CDER) are demonstrated via an array of characterization techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The catalytic mechanism of MoS2 toward CDRR/CDER is elucidated via XPS.