Enhancing Hydrogen Evolution Activity of Monolayer Molybdenum Disulfide via a Molecular Proton Mediator

The configuration and local environment of active sites in transition metal dichalcogenides can significantly alter their electrocatalytic activity toward the hydrogen evolution reaction (HER). Herein, we demonstrate that the HER activity of monolayer MoS2 electrocatalysts can be enhanced through the modulation of active sites by introducing a molecular mediator that alters the coverage of adsorbed protons. Sodium dodecyl sulfate (SDS) promotes the intrinsic HER activity of both terrace-based sulfur vacancies (VS) and edge sites during HER operation in an acidic environment, leading to increases in the turnover frequency (TOF) of both sites by up to 5 orders of magnitude. Simulations indicate that SDS facilitates proton adsorption by catching protons from hydronium ions and releasing them to VS, which reduces the energy barrier by creating a stair-case-like free energy profile. Our results highlight the ability to tailor the activity of electrocatalysts by synergistically combining proton transfer mediators with engineered active sites.

Automated summary

The study demonstrates that the hydrogen evolution reaction (HER) activity of monolayer MoS2 electrocatalysts can be significantly enhanced by modulating active sites through the introduction of a molecular mediator. Sodium dodecyl sulfate (SDS) is shown to promote the intrinsic HER activity of both terrace-based sulfur vacancies (VS) and edge sites, leading to up to 5 orders of magnitude increase in turnover frequency (TOF) for both sites. Simulations suggest that SDS facilitates proton adsorption by catching protons from hydronium ions and releasing them to VS, thereby reducing the energy barrier and creating a stair-case-like free energy profile.