# Strong Acid-Mediated Proton Transfer via Water Tunneling Fosters Hydrogen Evolution Reaction on MoS2 Derivatives under Alkaline Conditions

## TL;DR

Researchers found that adding acid-ended molecules to MoS2 nanoflakes improves hydrogen production efficiency even in alkaline conditions.

## Contribution

The study introduces a pH-insensitive electrocatalyst for hydrogen evolution by enhancing proton transfer via water tunneling.

## Key findings

- Surface-engineered MoS2 with sulfonic-acid groups boosts hydrogen evolution reaction (HER) under alkaline conditions.
- Weaker acid groups like benzoic acid do not promote proton transfer via tunneling.
- DFT calculations support the role of acidic moieties in water dissociation and tunneling at the surface.

## Abstract

The surface functionalization of chemically exfoliated
MoS2 (CE-MoS2) nanoflakes with
Brønsted-acid
end-capped aryl fragments adds an additional level of complexity to
the comprehension of the correlation between the electron-donating
strength of covalently grafted organic groups (Hammett parameter)
and the HER performance of these hybrids. MoS2 nanoflakes
decorated with aryl-sulfonic acids promote proton transfer via tunneling
of H-species, where weaker benzoic acid groups fail. Thus, surface-engineered CE-MoS2 bearing sulfonic-acid end-capped dangling
arms acts as an electrocatalyst that boosts HER kinetics even under
an alkaline environment, where water dissociation represents the bottleneck
of the process. Density functional theory (DFT) calculations have
been used to corroborate experimental evidence and speculate on the
role of acidic moieties with respect to water molecule tunneling and dissociation at the surface of the functionalized chalcogenide.
The study represents a significant advance in the development of pH-insensitive
electrocatalysts for HER.