Engineering grain boundaries at the 2D limit for the hydrogen evolution reaction

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Atom-thin transition metal dichalcogenides (TMDs) are crucial for electrocatalysis.
• Active sites for hydrogen evolution reaction (HER) in TMDs, such as edges and defects, have been studied.
• Grain boundaries (GBs) in TMDs, a type of defect, have been largely overlooked for HER due to low density and structural variability.

Purpose of the Study:

• To synthesize wafer-size atom-thin TMD films with ultra-high-density grain boundaries (GBs).
• To investigate the growth mechanism of these high-GB-density TMD films.
• To evaluate the electrocatalytic activity of TMD GBs for the hydrogen evolution reaction (HER).

Main Methods:

• Synthesis of wafer-size atom-thin TMD films with ultra-high GB density (~10^12 cm^-2).
• Proposal of a climb and drive 0D/2D interaction mechanism for TMD growth.
• Micro-electrochemical measurements to assess electrocatalytic performance.

Main Results:

• Successful synthesis of TMD films with unprecedented GB density.
• Elucidation of the TMD growth mechanism involving 0D/2D interactions.
• Demonstration of excellent HER performance with an onset potential of -25 mV and a Tafel slope of 54 mV dec^-1.

Conclusions:

• Grain boundaries (GBs) in TMDs are intrinsically highly active sites for HER.
• High-density GBs in TMDs significantly enhance electrocatalytic activity for water splitting.
• The findings open new avenues for designing efficient electrocatalysts based on TMD grain boundaries.