Gu Jinxing, Zhao Ziyuan, Huang Jingsong, Sumpter Bobby G, Chen Zhongfang
Department of Chemistry, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico 00931, United States.
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
ACS Nano. 2021 Apr 27;15(4):6233-6242. doi: 10.1021/acsnano.0c08429. Epub 2021 Mar 18.
Two-dimensional transition-metal compounds (2DTMCs) are promising materials for electrochemical applications, but 2DTMCs with metallicity and active basal planes are rare. In this work, we proposed a simple and effective strategy to extract 2DTMCs from non-van der Waals bulk materials and established a material library of 79 2DTMCs, which we named as anti-MXenes since they are composed of one M atomic layer sandwiched by two X atomic layers. By means of density functional theory computations, 24 anti-MXenes were confirmed to be thermodynamically, dynamically, mechanically, and thermally stable. The metallicity and active basal plane endow these anti-MXenes with potential as excellent electrode materials, for example, as electrocatalysts for hydrogen evolution reactions (HER). Among the noble-metal free anti-MXenes with favorable H-binding, CuS can boost HER at the whole range of H coverages, while CoSi, FeB, CoB, and CoP show promise for HER at some specific H coverages. The active sites are the tetra-coordinating nonmetal atoms at the basal planes, thus rendering a very high density of active sites for these materials. CoB is also a promising anode material for lithium-ion batteries, showing low Li diffusion energy barriers, a very high capacity, and a suitable open circuit voltage. This work promotes the "computational exfoliation" of 2D materials from non-van der Waals bulks and exemplifies the applications of anti-MXenes in various electrochemical processes.
二维过渡金属化合物（2DTMCs）是电化学应用中有前景的材料，但具有金属性和活性基面的2DTMCs却很罕见。在这项工作中，我们提出了一种简单有效的策略，从非范德华体材料中提取2DTMCs，并建立了一个包含79种2DTMCs的材料库，我们将其命名为反式MXenes，因为它们由一个M原子层夹在两个X原子层之间组成。通过密度泛函理论计算，证实了24种反式MXenes在热力学、动力学、力学和热学上是稳定的。金属性和活性基面使这些反式MXenes具有作为优异电极材料的潜力，例如，作为析氢反应（HER）的电催化剂。在具有良好氢结合的无贵金属反式MXenes中，CuS在整个氢覆盖范围内都能促进HER，而CoSi、FeB、CoB和CoP在某些特定的氢覆盖范围内显示出析氢反应的潜力。活性位点是基面处的四配位非金属原子，因此这些材料具有非常高的活性位点密度。CoB也是一种有前景的锂离子电池负极材料，具有低锂扩散能垒、非常高的容量和合适的开路电压。这项工作促进了从非范德华体中“计算剥离”二维材料，并例证了反式MXenes在各种电化学过程中的应用。
