The kinetics and potential dependence of the hydrogen evolution reaction optimized for the basal-plane Te vacancy site of MoTe₂

Electrocatalysis at the edge sites of transition-metal dichalcogenides has been well studied, particularly for the hydrogen evolution reaction (HER). Here, we explore instead the HER activity on the basal plane of MoTe₂ by creating anion vacancies via computational predictions followed by experimental validation. Using the grand canonical potential kinetics method, we predict that overpotentials of 535 and 565 mV can achieve a current density of 10 mA cm⁻² for 1T′-MoTe₂ and 2H-MoTe₂ containing 1.14 x 10¹⁴ cm⁻² and 3.45 x 10¹³ cm⁻² Te vacancies, respectively. This is in good agreement with experimental overpotentials of 561 and 634 mV for 1T′-MoTe₂ and 2H-MoTe₂ containing similar vacancies ( 1.28 x 10¹⁴ cm⁻² and 3.54 x 10¹³ cm⁻², respectively). Furthermore, we used Ar plasma treatment to increase the Te vacancy on the basal plane and found an optimal vacancy concentration of 3.18 x 10¹⁴ cm⁻² for 1T′-MoTe₂ and 1.02 x 10¹⁴ cm⁻² for 2H-MoTe₂. Increasing or decreasing the vacancy concentrations from this level further reduces HER performance.