Transparent proton transport through a two-dimensional nanomesh material

Jiyu Xu,Sheng Meng,Xin-Zheng Li,E. G. Wang,Hongyu Jiang,Yutian Shen

doi:10.1038/s41467-019-11899-y

Abstract

Molecular sieving is of great importance to proton exchange in fuel cells, water desalination, and gas separation. Two-dimensional crystals emerge as superior materials showing desirable molecular permeability and selectivity. Here we demonstrate that a graphdiyne membrane, an experimentally fabricated member in the graphyne family, shows superior proton conductivity and perfect selectivity thanks to its intrinsic nanomesh structure. The trans-membrane hydrogen bonds across graphdiyne serve as ideal channels for proton transport in Grotthuss mechanism. The free energy barrier for proton transfer across graphdiyne is ~2.4 kJ mol−1, nearly identical to that in bulk water (2.1 kJ mol−1), enabling “transparent” proton transport at room temperature. This results in a proton conductivity of 0.6 S cm−1 for graphdiyne, four orders of magnitude greater than graphene. Considering its ultimate pore size of 0.55 nm, graphdiyne membrane blocks soluble fuel molecules and exhibits superior proton selectivity. These advantages endow graphdiyne a great potential as proton exchange material.

Highlights

IntroductionMolecular sieving is of great importance to proton exchange in fuel cells, water desalination, and gas separation
Molecular sieving is of great importance to proton exchange membranes (PEMs) for fuel cells (FCs)[1,2], water desalination[3], and gas separation[4]
The two sets of equilibrium ab initio molecular dynamics (AIMD) simulations were performed with two different initial positions of H3O+ complexes. (The definition of proton position is shown in Supplementary Fig. 1 and Supplementary Note 1.) In the first group, a H3O+ complex is initially located in the bulk water layers below the membrane, while a H3O+ complex is put directly beneath the nanopore of the graphdiyne membrane in the second group

Summary

Introduction

Molecular sieving is of great importance to proton exchange in fuel cells, water desalination, and gas separation. The free energy barrier for proton transfer across graphdiyne is ~2.4 kJ mol−1, nearly identical to that in bulk water (2.1 kJ mol−1), enabling “transparent” proton transport at room temperature. Considering its ultimate pore size of 0.55 nm, graphdiyne membrane blocks soluble fuel molecules and exhibits superior proton selectivity. These advantages endow graphdiyne a great potential as proton exchange material. 1234567890():,; Molecular sieving is of great importance to proton exchange membranes (PEMs) for fuel cells (FCs)[1,2], water desalination[3], and gas separation[4]. We demonstrate using extensive ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) calculations that graphdiyne membrane exhibits superior proton conductivity and selectivity in aqueous solutions at room temperature (Fig. 1).

Methods

Results

Conclusion