Revisiting the Role of Active Sites for Hydrogen Evolution Reaction through Precise Defect Adjusting

2D transition metal dichalcogenides (TMDs) have presented outstanding potential for efficient hydrogen evolution reaction (HER) to replace traditional noble metal catalysts. Here, to achieve enhanced HER performance, specific areas of the few-layer 1T'-MoTe2 film are precisely controlled with a focused ion beam to create particular active sites. Electrochemical measurements indicate that the HER performance, although inconspicuous in pristine 1T'-MoTe2 ultrathin films prepared through the chemical vapor deposition method, can be greatly enhanced after patterning and precisely controlled by the morphologies as well as the amounts of the defects, reaching a small onset potential and a record-low Tafel slope of 44 mV per decade for few-layer TMDs. Conductivity tests, visualized copper electrodeposition, and density functional theory calculations also confirm that the enhancement of HER performance comes from the exposed edges by patterning. In this pioneering work, not only is the catalysis mechanism of the edge active sites of 1T'-MoTe2 unveiled, but also a universal route to study the properties of 2D materials is demonstrated.