Field Effect Modulation of Electrocatalytic Hydrogen Evolution at Back-Gated Two-Dimensional MoS₂ Electrodes

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• Monolayer MoS₂ is a promising electrocatalyst for hydrogen evolution.
• Controlling electronic properties is key to enhancing catalytic activity.
• Electric field modulation offers a novel approach to tune catalyst performance.

Purpose of the Study:

• To investigate the effect of an applied electric field on the electrocatalytic activity of monolayer MoS₂ for hydrogen evolution.
• To explore the mechanism behind field-induced enhancement of catalytic activity.
• To demonstrate the utility of a back-gated electrode architecture for studying electrocatalysis.

Main Methods:

• Fabrication of a back-gated device with monolayer MoS₂ on a dielectric.
• Electrochemical measurements in 0.5 M H₂SO₄, including potential sweeps and Tafel analysis.
• Density Functional Theory (DFT) calculations to model the electronic structure and bonding.

Main Results:

• Application of a normal electric field reduced the overpotential for hydrogen evolution by up to 140 mV at 50 mA/cm².
• Exchange current density improved by a factor of four (to 0.1 mA/cm²) with increasing gate voltage.
• DFT calculations revealed gate-induced charge increase on Mo sites, strengthening Mo-H bonds.

Conclusions:

• Electric field modulation is an effective strategy to enhance electrocatalytic hydrogen evolution on monolayer MoS₂.
• The back-gated architecture provides a versatile platform for tuning active site electronic charge and studying electrocatalytic processes.
• Understanding the relationship between electronic charge and overpotential is crucial for designing efficient electrocatalysts.