Interlayer Spacing Regulation of Molybdenum Selenide Promotes Electrocatalytic Hydrogen Evolution in Alkaline Media.

The construction of heterostructures is a versatile tactic to enhance catalytic activity. However, it is still elusive to realize the modulation of the interlayer spacing in this way to further improve the performance. Here, strong interfacial coupling between CoSe 2 and MoSe 2 by constructing CoSe 2 /MoSe 2 heterostructures is achieved. The interlayer spacing of MoSe 2 is compressed by 0.3 Å. The enhanced charge transfer is validated by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. Coupled with the morphology of hollow microtubes, which can facilitate the exposure of active sites, CoSe 2 /MoSe 2 heterostructures reported here exhibit high activity (119 mV at 10 mA cm -2 ) and excellent stability with small degradation after 50 h operation, surpassing other analogous powdered electrocatalysts. This work sheds light on the importance of tuning the interlayer spacing to improve electrocatalytic activity.