Electrochemically deposited transition metal dichalcogenide heterostructures as electrocatalysts: Accelerated kinetics for the hydrogen evolution reaction

Transition metal dichalcogenide (TMD) heterostructures have been discovered to have improved catalytic activity towards the hydrogen evolution reaction (HER). This study explores the stability and HER catalytic activity including reaction kinetics of heterolayers of different TMDs (MoS₂, MoSe₂ and WS₂). The stability of the heterolayers varied with those having an overlayer of electrodeposited MoS₂ being more stable as compared to those with MoSe₂ overlayer which degraded with each scan in acidic media. Investigation into the HER kinetics of the heterolayers involved Tafel analysis and electrochemical rate constant calculation. There was an improvement in Tafel values calculated in comparison to reported values for these heterolayers. WS₂/MoS₂ and MoSe₂/MoS₂ heterolayers registered rate constants of (3.20 ± 0.10) × 10⁻⁴ cm s⁻¹ and (1.73 ± 0.03) × 10⁻⁴ cm s⁻¹ respectively, which was an improvement of up to an order of magnitude compared to the reported rate constant of electrodeposited MoS₂ of (3.17 ± 0.30) × 10⁻⁵ cm s⁻¹. All this highlights the improved HER catalytic activity of the heterolayers.