Description
Date/Time: 04-04-2018 - Wednesday - 05:00 PM - 07:00 PM
Ryland Forsythe1 Boniface Fokwa1

1, University of California, Riverside, Riverside, California, United States

MXenes are a class of 2D materials first developed by Michael Naguib, Yury Gogotsi and Michel Barsoum at Drexel University in 2011.[1] They are created by etching out the A layer of layered Mn+1AXn phases (M=transition metal, A=group 13 or 14 element, X=C,N) with n=1, 2, or 3, resulting in loose stacks of MX slabs. These slabs can then be exfoliated into 2D sheets, dubbed MXenes. The MXenes have a range of interesting properties depending on composition, surface termination, and synthesis conditions.[2] More recently a similar class of compounds have attracted attention: MnABn (B=boron) phases have a similar layering structure, and also show anisotropic properties.[3] The bulk boride phases possess a couple properties unique from the MAX phases, including high temperature stability and outstanding hardness. To date, 2D MBene sheets have not been created, and very little attention has been given to them in the literature. However, theoretical work suggests that these materials show great promise as battery electrodes, catalysts, and capacitors.[4],[5] In view of this, we have discovered a novel synthesis toward 2D MBene layers from the M2AlB2 (M=Cr, Mn, Fe) structure. The partial etching of the bulk phase can be finely controlled by tuning the starting composition, creating different porous scaffolds. The exposed surface contains the same active sites as in MoB2 and FeB2,[5],[6] which have recently been reported for their excellent catalytic activity. The HER activity of these new 2D Mbenes will be presented.

References
1. Naguib, M. et al. Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Adv. Mater. 23, 4248–4253 (2011).
2. Hong Ng, V. M. et al. Recent progress in layered transition metal carbides and/or nitrides (MXenes) and their composites: synthesis and applications. J. Mater. Chem. A 5, 3039–3068 (2017).
3. Ade, M. & Hillebrecht, H. Ternary Borides Cr 2 AlB 2 , Cr 3 AlB 4 , and Cr 4 AlB 6 : The First Members of the Series (CrB 2 ) n CrAl with n = 1, 2, 3 and a Unifying Concept for Ternary Borides as MAB-Phases. Inorg. Chem. 54, 6122–6135 (2015).
4. Guo, Z., Zhou, J. & Sun, Z. New Two-dimensional Transition Metal Borides for Li Ion Battery and Electrocatalysis. J. Mater. Chem. A (2017). doi:10.1039/C7TA08665B
5. Park, H., Encinas, A., Scheifers, J. P., Zhang, Y. & Fokwa, B. P. T. Boron-Dependency of Molybdenum Boride Electrocatalysts for the Hydrogen Evolution Reaction. Angew. Chemie - Int. Ed. 56, 5575–5578 (2017).
6. Li, H. et al. Earth-Abundant Iron Diboride (FeB2) Nanoparticles as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting. Adv. Energy Mater. 7, 1700513 (2017).

Meeting Program
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5:00 PM–7:00 PM Apr 4, 2018

PCC North, 300 Level, Exhibit Hall C-E