Flower-petal-like Nb₂C MXene combined with MoS₂ as bifunctional catalysts towards enhanced lithium-sulfur batteries and hydrogen evolution

Efficient catalysts designed by reasonable heterostructure engineering have a bright prospect for lithium-sulfur batteries (LSBs) and hydrogen evolution reaction (HER). Here, we determined Nb₂C MXene and MoS₂ to form heterojunction due to their high lattice adaptation. The unique flower-petal-like Nb₂C MXene was prepared by freeze-drying, the MoS₂ growing on the surface of Nb₂C MXene by hydrothermal method. We applied the MoS₂/Nb₂C hybrids to LSB for the first time. The MoS₂/Nb₂C hybrids showed a specific capacity of 919.2 mAh g⁻¹ at 0.2 C after 200 cycles with excellent retention of 92.2% when used as the cathode of LSBs. The MoS₂/Nb₂C electrode was used for HER under alkaline condition, which showed a Tafel slope of 65.1 mV dec⁻¹, an overpotential of 117 mV at 10 mA cm⁻² and excellent long-term robustness of HER performance. The mechanism of excellent properties of LSBs and HER activity were explained from the perspective of adsorption energy calculated according to the first principles. The adsorption activity of the MoS₂/Nb₂C heterojunction is much higher than that of bare MoS₂ from the point of view of lithium polysulfides (LiPS) and hydrogen atoms. The heterostructure engineering of the MoS₂/Nb₂C hybrids is of guiding significance for green energy and energy conversion.