Topochemical Deintercalation of Al from MoAlB: Stepwise Etching Pathway, Layered Intergrowth Structures, and Two-Dimensional MBene

Lucas T. Alameda, Parivash Moradifar, Zachary P. Metzger, Nasim Alem, Raymond Edward Schaak

Research output: Contribution to journalArticle

36 Scopus citations

Abstract

The synthesis of refractory materials usually relies on high-temperature conditions to drive diffusion-limited solid-state reactions. These reactions result in thermodynamically stable products that are rarely amenable to low-temperature topochemical transformations that postsynthetically modify subtle structural features. Here, we show that topochemical deintercalation of Al from MoAlB single crystals, achieved by room-temperature reaction with NaOH, occurs in a stepwise manner to produce several metastable Mo-Al-B intergrowth phases and a two-dimensional MoB (MBene) monolayer, which is a boride analogue to graphene-like MXene carbides and nitrides. A high-resolution microscopic investigation reveals that stacking faults form in MoAlB as Al is deintercalated and that the stacking fault density increases as more Al is removed. Within nanoscale regions containing high densities of stacking faults, four previously unreported Mo-Al-B (MAB) intergrowth phases were identified, including Mo 2 AlB 2 , Mo 3 Al 2 B 3 , Mo 4 Al 3 B 4 , and Mo 6 Al 5 B 6 . One of these deintercalation products, Mo 2 AlB 2 , is identified as the likely MAB-phase precursor that is needed to achieve a high-yield synthesis of two-dimensional MoB, a highly targeted two-dimensional MBene. Microscopic evidence of an isolated MoB monolayer is shown, demonstrating the feasibility of using room-temperature metastable-phase engineering and deintercalation to access two-dimensional MBenes.

Original languageEnglish (US)
Pages (from-to)8833-8840
Number of pages8
JournalJournal of the American Chemical Society
Volume140
Issue number28
DOIs
StatePublished - Jul 18 2018

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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