Large-area synthesis of monolayered MoS_2(1−x)Se_2x with a tunable band gap and its enhanced electrochemical catalytic activity

Abstract

"Band gap engineering" in two-dimensional (2D) materials plays an important role in tailoring their physical and chemical properties. The tuning of the band gap is typically achieved by controlling the composition of the semiconductor alloys. However, large-area preparation of 2D alloys remains a major challenge. Here, we report the large-area synthesis of high-quality monolayered MoS2(1-x)Se2x with a size coverage of hundreds of microns using a chemical vapor deposition method. The photoluminescence (PL) spectroscopy results confirm the tunable band gap in MoS2(1-x)Se2x, which is modulated by varying the Se content. Atomic-scale analysis was performed and the chemical composition was characterized using high-resolution scanning transmission electron microscopy and X-ray photoemission spectroscopy. With the introduction of Se into monolayered MoS2, it leads to enhanced catalytic activity in an electrochemical reaction for hydrogen generation, compared to monolayered MoS2 and MoSe2. It is promising as a potential alternative to expensive noble metals.

Two-Dimensional Material Molybdenum Disulfides as Electrocatalysts for Hydrogen Evolution

“…Our group synthesized monolayer MoS2(1−x)Se2x alloys and MoS2(1−x)Se2x nanobelt alloys via a CVD method by using MoO3, S powder, and Se powder as reactants [69,73]. By adjusting the weight ratio of S and Se powders, the monolayer MoS2(1−x)Se2x and MoS2(1−x)Se2x nanobelt alloys with different Se contents can be achieved.…”

“…Another efficient way to enhance the HER performance of MoS2 is to form MoS2-based alloys [69][70][71][72][73]. Our group synthesized monolayer MoS2(1−x)Se2x alloys and MoS2(1−x)Se2x nanobelt alloys via a CVD method by using MoO3, S powder, and Se powder as reactants [69,73].…”

“…[69]. (e) Polarization curves and (f) Tafel plots of monolayer MoS2(1−x)Se2x with different Se contents [69]. Reproduced from [68] with permission from copyright 2016 Nature Publishing Group and [69] with permission from copyright 2015 The Royal Society of Chemistry.…”

“…The Tafel slope and the TOFs-vacancy (at 0 V versus RHE) for the strained MoS 2 with S-vacancy were 60 mV/dec and 0.08-0.31 s −1 , respectively, better than that that of strained MoS 2 without S-vacancy, the unstrained MoS 2 with S-vacancy, as well as the transferred MoS 2 (Figure 8c). [69]. (e) Polarization curves and (f) Tafel plots of monolayer MoS2(1−x)Se2x with different Se contents [69].…”

“…We summarize the HER performance of a variety of MoS2 catalysts mentioned above in Table 1. [69]. (e) Polarization curves and (f) Tafel plots of monolayer MoS 2(1−x) Se 2x with different Se contents [69].…”