Proton dynamics in water confined at the interface of the graphene-MXene heterostructure

TL;DR

This study uses ab initio molecular dynamics to explore proton transfer, diffusion, and redox behavior in water confined at the graphene-MXene heterostructure interface, revealing how interfacial structure influences proton mobility and redox rates.

Contribution

It provides new insights into how dissimilar interfaces affect proton dynamics and redox processes in 2D material heterostructures, highlighting the role of interfacial structure and electric fields.

Findings

Proton redox rate is higher at the graphene-MXene interface compared to similar MXene interfaces.

Denser hydrogen-bond networks increase proton mobility with concentration.

Proton mobility decreases at high concentrations due to surface redox binding.

Abstract

Heterostructures of 2D materials offer a fertile ground to study ion transport and charge storage. Here we employ ab initio molecular dynamics to examine the proton-transfer/diffusion and redox behavior in a water layer confined in the graphene-Ti3C2O2 heterostructure. We find that in comparison with the similar interface of water confined between Ti3C2O2 layers, proton redox rate in the dissimilar interface of graphene-Ti3C2O2 is much higher, owning to the very different interfacial structure as well as the interfacial electric field induced by an electron transfer in the latter. Water molecules in the dissimilar interface of the graphene-Ti3C2O2 heterostructure form a denser hydrogen-bond network with a preferred orientation of water molecules, leading to an increase of proton mobility with proton concentration in the graphene-Ti3C2O2 interface. As the proton concentration further increases, proton mobility deceases, due to increasingly more frequent surface redox events that slow down proton mobility due to binding with surface O atoms. Our work provides important insights into how the dissimilar interface and their associated interfacial structure and properties impact proton transfer and redox in the confined space.