Synthesis of 1T-MoSe₂ ultrathin nanosheets with an expanded interlayer spacing of 1.17 nm for efficient hydrogen evolution reaction

In this work, we report for the first time a simple solvothermal method to synthesize assembled 1T-MoSe₂ nanosheets, which possess expanded (002) interlayer spacings as large as 1.17 nm with an 81% expansion as compared to that (0.646 nm) of the bulk counterpart. The 1T-MoSe₂ nanosheets exhibit striking kinetic metrics for the hydrogen evolution reaction (HER) with a low onset potential of 60 mV and a small Tafel slope of 78 mV dec^-1, which are better than those of the 2H-MoSe₂ counterpart with a normal interlayer spacing of 0.64 nm. The outstanding electrocatalytic activity is attributed to the high concentration of the metallic 1T phase as well as the expanded interlayer distance, contributing to increasing the number and catalytic activity of the active sites.