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 MoS_2(1−x)N_x, 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 d_z²(Mo), p_z(S), and p_z(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.