Dehydration-Determined Ion Selectivity of Graphene Subnanopores

Yanjun Fu; Shihao Su; Ning Zhang; Yihan Wang; Xun Guo; Jianming Xue

doi:10.1021/acsami.0c03932

Dehydration-Determined Ion Selectivity of Graphene Subnanopores

ACS Appl Mater Interfaces. 2020 May 27;12(21):24281-24288. doi: 10.1021/acsami.0c03932. Epub 2020 May 12.

Authors

Yanjun Fu^{1

2}, Shihao Su^{1

2}, Ning Zhang^{1

2}, Yihan Wang^{1

2}, Xun Guo¹, Jianming Xue^{1

2}

Affiliations

¹ State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, P. R. China.
² CAPT, HEDPS, College of Engineering, Peking University, Beijing 100871, P. R. China.

PMID: 32349478
DOI: 10.1021/acsami.0c03932

Abstract

Graphene membranes with subnanopores are considered to be the next-generation materials for water desalination and ion separation, while their performance is mainly determined by the relative ion selectivity of the pores. However, the origin of this phenomenon has been controversial in the past few years, which strongly limits the development of related applications. Here, using direct Au ion bombardment, we fabricated the desired subnanopores with average diameters of 0.8 ± 0.16 nm in monolayer graphene. The pores showed the ability to sieve K⁺, Na⁺, Li⁺, Cs⁺, Mg²⁺, and Ca²⁺ cations, and the observed K⁺/Mg²⁺ selectivity ratio was over 4. With further molecular dynamics simulations, we demonstrated that the ion selectivity is primarily attributed to the dehydration process of ions that can be quantitatively described by the ion-dependent free-energy barriers. Hopefully, this work is helpful in further enhancing the ion selectivity of graphene nanopores and also presenting a new paradigm for improving the performance of other nanoporous atomically thin membranes, such as MXenes and MoS₂.

Keywords: MD simulations; dehydration; graphene nanopore; ion irradiation; ion selectivity.