# Hydrogenation Facilitates Proton Transfer Through Two-Dimensional Honeycomb Crystals

## TL;DR

This study demonstrates that hydrogenation of two-dimensional honeycomb crystals like graphene and h-BN significantly lowers the energy barrier for proton transfer, explaining rapid proton transport observed experimentally.

## Contribution

First principles calculations reveal hydrogenation reduces proton penetration barriers in 2D materials, enabling fast proton transfer without lattice defects.

## Key findings

- Hydrogenation lowers proton penetration barrier to less than 1 eV.
- Destabilization of chemisorption states facilitates proton transfer.
- Hydrogenated 2D materials enable efficient proton transport in solutions.

## Abstract

Recent experiments have triggered a debate about the ability of protons to transfer through individual layers of graphene and hexagonal boron nitride (h-BN). However, calculations have shown that the barriers to proton penetration can, at more than 3 eV, be excessively high. Here, on the basis of first principles calculations, we show that the barrier for proton penetration is significantly reduced, to less than 1 eV, upon hydrogenation even in the absence of pinholes in the lattice. Analysis reveals that the barrier is reduced because hydrogenation destabilises the initial state (a deep-lying chemisorption state) and expands the honeycomb lattice through which the protons penetrate. This study offers a rationalization of the fast proton transfer observed in experiments, and highlights the ability of proton transport through single-layer materials in hydrogen rich solutions.