Enabling Colloidal Synthesis of Edge-Oriented MoS₂ with Expanded Interlayer Spacing for Enhanced HER Catalysis

Area of Science:

• Materials Science
• Nanotechnology
• Electrochemistry

Background:

• Molybdenum disulfide (MoS2) is a promising material for catalysis.
• Developing efficient and scalable synthesis methods for MoS2-based catalysts is crucial.
• Heterogeneous nucleation and growth strategies can control material morphology and properties.

Purpose of the Study:

• To synthesize edge-oriented (EO) MoS2 nanosheets with expanded interlayer spacing (EO&IE) on reduced graphene oxide (rGO).
• To investigate the catalytic activity of EO&IE MoS2/rGO for the hydrogen evolution reaction (HER).
• To understand the synergistic effects of edge-orientation and interlayer expansion on HER performance.

Main Methods:

• Colloidal chemistry approach for selective heterogeneous nucleation and growth of MoS2 on graphene.
• Microwave-assisted solvothermal reduction of ammonium tetrathiomolybdate in dimethylformamide.
• Tuning MoS2 nanosheet density and edge length by controlling reaction time.

Main Results:

• Successfully synthesized EO MoS2 nanosheets with expanded interlayer spacing (~9.4 Å) on rGO.
• EO&IE MoS2/rGO demonstrated significantly improved HER catalytic activity compared to MoS2 without edge-orientation.
• Achieved higher current density, lower Tafel slope, and reduced charge transfer resistance.
• Quantified a linear dependence of current density on the edge length of MoS2 nanosheets.

Conclusions:

• The synergistic effect between edge-oriented geometry and interlayer expansion is critical for enhancing HER activity in MoS2 nanosheets.
• The developed method offers a promising route for low-cost and large-scale production of efficient HER electrocatalysts.
• Controlling the morphology of MoS2 nanosheets, specifically edge length, directly impacts catalytic performance.