The âMAXâ-phase of over 100 ternary carbides/nitrides was first identified in the 1960s.[1] The nomenclature is an abbreviation of the general formula of these 2D material âMn+1AXnâ, whereby M denotes a transition metal and A/X represent an A group element and carbon/nitrogen respectively.[2] They also display a very novel combination of properties including high conductivity and extreme resistance to oxidation or heating,[3] which has led to these materials being labelled as âmetallic ceramicsâ.[4] Structurally, the surfaces of these materials strongly resemble the pristine (111) facets of early transition metal carbides (TMCs), which have themselves been shown to be efficient catalysts for the hydrogenation of CO2.[5] Our group has previously undertaken a detailed in silico study into the catalytic activity of the equivalent TMCs to the MAX-phase material under investigation in this work and found the metal terminated (111) facets to be extremely active for CO2 reduction.[6] The choice of the transition metal components was partly informed by this study and partly by a systematic screening of the bulk and surface properties of a diverse array of carbides.[7] This talk will focus on work recently published in the carbon dioxide utilisation theme of Faraday Discussion that concerns computational insights into the bulk and catalytic properties of Ti4SiC3, V4SiC3, Nb4SiC3 & Zr4SiC3 and compare these properties to those already obtained for TiC, VC, NbC & ZrC.[8] We will show that the addition of an intestinal silicon layer into the bulk of these material increases the lattice paraments beyond those observe for the corresponding carbides. We also show that the pristine surfaces of the MAX-phase materials are much more active towards CO2, H2, H2O and OH. However, our results demonstrate that pristine surfaces are not likely to be present in an oxygenating environment.
References
[1] W. Jeitschko, H. Nowotny and F. Benesovsky, Monatshefte fĂŒr Chemie,1963, 94, 672â676.
[2] Z. M. Sun, Int. Mater. Rev., 2011, 56, 143â166.
[3] P. Eklund, M. Beckers, U. Jansson, H. Högberg and L. Hultman, Thin Solid Films, 2010, 518, 1851â1878.
[4] Z. M. Sun, H. Hashimoto, Z. F. Zhang, S. L. Yang and S. Tada, Mater. Trans., 2006, 47, 170â174.
[5] M. D. Porosoff, S. Kattel, W. Li, P. Liu and J. G. Chen, Chem. Commun., 2015, 51, 6988â6991.
[6] M. G. Quesne, A. Roldan, N. H. de Leeuw and C. R. A. Catlow, Phys. Chem. Chem. Phys., 2019, 21, 10750â10760. [7] M. G. Quesne, A. Roldan, N. H. De Leeuw and C. R. A. Catlow, Phys. Chem. Chem. Phys., 2018, 20, 6905â6916.
[8] M. G. Quesne, C. R. A. Catlow and N. H. De Leeuw, Faraday Discuss., 2021, [in press] DOI:10.1039/D1FD00004G
Dr. Matthew Quesne undertook a PhD at the Manchester Institute of Biotechnology under the supervision of Dr Sam de Visser, in the fields of bio-mimetic and enzyme catalysis. He focused on modelling the catalytic activity of synthetic complexes of transition metal dependent homogeneous catalysts. Over the four years spent at Manchester he worked with dozens of different experimental groups and provided the in silico components to many joint computational/experimental studies. He joined the research group headed by Dr Tomasz Borowski at the Institute of Catalysis and Surface Chemistry Polish Academy of Science in Krakow (Poland) in November 2014, where he spent two years using MD, QM/MM and cluster model techniques to model enzyme catalysed reaction mechanisms. In 2016, he moved to Cardiff to work in Prof. Catlowâs group where he studied CO2 activation on a variety of transition metal carbides. This work formed a small part of a much larger EPSRC project that aimed to bring together several groups from across the UK in a multi-disciplinary fashion in order to develop integrated techniques for utilising CO2 as a feedstock for the production of fuels and fine chemicals. Matthew started his position with the UK Catalysis Hub in March of 2019 and is focused on the intersection of the modelling of heterogenously and homogenously catalysed reaction mechanisms.
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