Mo 2 C MXene Nanosheets Made in Different Etching Solutions as Co-catalysts for Hydrogen Production

Mo 2 C MXene is a two-dimensional material, which can be applied as a co-catalyst to significantly enhance the photocatalytic performance of CdS for H 2 production. To understand the effect of the synthesis process of Mo 2 C MXene nanosheets on the catalytic performance, in this paper, Mo 2 C MXene was made from Mo 2 Ga 2 C by hydrothermal etching in different etchants. Diverse cations (Li +, Na +, K +, or NH 4 + ) in etchants resided on the surface of Mo 2 C MXene nanosheets. Then, the samples were used to construct CdS/Mo 2 C-MXene composites for photocatalytic H 2 evolution. Among them, Mo 2 C MXene with Li + shows the best photocatalytic H 2 production rate of 22,048 μmol g –1 h –1 under visible light. The remarkable performance arises from the modification at the nanoscale of Mo 2 C MXene with Li +, thereby resulting in better photoabsorption behavior, high separation efficiency of photogenerated carriers, and fast charge transfer at the heterointerface. Moreover, the energy band structures explain that the changes of band gap and the position of the conductive band in the photocatalyst tuned by cations are also key to affect photocatalytic activities.