Revealing the innate sub-nanometer porous structure of carbon nanomembranes with molecular dynamics simulations and highly charged ion spectroscopy

TL;DR

This study combines molecular dynamics simulations and highly charged ion spectroscopy to uncover the sub-nanometer porous structure of carbon nanomembranes, revealing their composition and potential reactivity.

Contribution

It introduces a novel approach to characterize CNMs' structure-property relationships without damaging the membrane, using simulations and ion spectroscopy comparison.

Findings

CNMs likely contain under-coordinated carbon atoms

CNMs have an open sub-nanometer porous structure

The structure is stabilized by hydrogen and oxygen groups in atmosphere

Abstract

Carbon nanomembranes (CNMs) are nanometer-thin disordered carbon materials that are suitable for a range of applications, from energy generation and storage, through to water filtration. The structure-property relationships of these nanomembranes are challenging to study using traditional experimental characterization techniques, primarily due to the radiation-sensitivity of the free-standing membrane. Highly charged ion spectroscopy is a novel characterization method that is able to infer structural details of the carbon nanomembrane without concern of induced damage affecting the measurements. Here we employ molecular dynamics simulations to produce candidate structural models of terphenylthiol-based CNMs with varying degrees of nanoscale porosity, and compare predicted ion charge exchange data and tensile moduli to experiment. The results suggest that the in-vacuum CNM composition likely comprises a significant fraction of under-coordinated carbon, with an open sub-nanometer porous structure. Such a carbon network would be reactive in atmosphere and would be presumably stabilized by hydrogen and oxygen groups under atmospheric conditions.