Nitrogen-rich 1T'-MoS2 layered nanostructures using alkyl amines for high catalytic performance toward hydrogen evolution.

Abstract

The imminent global energy crisis and current environmental issues have stimulated considerable research on high-performance catalysts for sustainable hydrogen energy generation. Two-dimensional layered MoS2 has recently drawn worldwide attention because of its excellent catalytic properties for the hydrogen evolution reaction (HER). In the present work, we prepared nitrogen (N)-rich 1T' (distorted 1T) phase MoS2 layered nanostructures using different alkyl amines with 1-4 nitrogen atoms (methylamine, ethylenediamine, diethylenetriamine, and triethylenetetramine) as intercalants. The amine molecules intercalate at 10 atomic%, and simultaneously supply the N atoms that substitute the S atoms to produce the N-doped MoS2, whose composition is MoS2(1-x)Nx, where x = 0.1-0.26. MoS2 prepared with amines having more N atoms has enhanced catalytic HER performance: a Tafel slope of 36 mV dec-1 and 10 mA cm-2 at -160 mV (vs. RHE). First-principles calculations showed that the amine intercalation and N doping increase the density of states near the Fermi level in a narrow range and bring about an effective overlap of the dz2(Mo), pz(S), and pz(N) states. These factors in turn increase the carrier (electron) concentration and mobility for improved HER. The calculation also predicted that the most active site is S vacancies. The present work illustrates how the HER catalytic performance of 1T' phase MoS2 can be effectively controlled by the amine molecules.