The electron-rich characteristic and low work function endow electrides with excellent performance in (opto)electronics and catalytic applications; these two features are closely related to the structural topology, constituents, and valence electron concentration of electrides. However, the synthesized electrides, especially two-dimensional (2D) electrides, are limited to specific structural prototypes and anionic p-block elements. Here we synthesize and identify a distinct 2D electride of BaCu with delocalized anionic electrons confined to the interlayer spaces of the BaCu framework. The bonding between Cu and Ba atoms exhibits ionic characteristics, and the adjacent Cu anions form a planar honeycomb structure with metallic Cu–Cu bonding. The negatively charged Cu ions are revealed by the theoretical calculations and experimental X-ray absorption near-edge structure. Physical property measurements reveal that BaCu electride has a high electronic conductivity (ρ = 3.20 μΩ cm) and a low work function (2.5 eV), attributed to the metallic Cu–Cu bonding and delocalized anionic electrons. In contrast to typical ionic 2D electrides with p-block anions, density functional theory calculations find that the orbital hybridization between the delocalized anionic electrons and BaCu framework leads to unique isotropic physical properties, such as mechanical properties, and work function. The freestanding BaCu monolayer with half-metal conductivity exhibits low exfoliation energy (0.84 J/m²) and high mechanical/thermal stability, suggesting the potential to achieve low-dimensional BaCu from the bulk. Our results expand the space for the structure and attributes of 2D electrides, facilitating the discovery and potential application of novel 2D electrides with transition metal anions.

中文翻译：

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BaCu，一种带有 Cu 阴离子的二维电子化合物


富电子特性和低功函数赋予电子化合物在（光）电子和催化应用中优异的性能；这两个特征与电子化合物的结构拓扑、成分和价电子浓度密切相关。然而，合成的电子化合物，特别是二维（2D）电子化合物，仅限于特定的结构原型和阴离子p区元素。在这里，我们合成并鉴定了一种独特的 BaCu 二维电子化合物，其离域阴离子电子被限制在 BaCu 框架的层间空间。 Cu 和 Ba 原子之间的键合表现出离子特性，相邻的 Cu 阴离子形成具有金属 Cu-Cu 键合的平面蜂窝结构。通过理论计算和实验X射线吸收近边缘结构揭示了带负电的Cu离子。物理性质测量表明，BaCu 电子化合物具有高电子电导率（ρ = 3.20 μΩ cm）和低功函数（2.5 eV），这归因于金属 Cu-Cu 键合和离域阴离子电子。与具有 p 区阴离子的典型离子二维电子化合物相比，密度泛函理论计算发现离域阴离子电子与 BaCu 骨架之间的轨道杂化导致独特的各向同性物理性能，例如机械性能和功函数。具有半金属导电性的独立式 BaCu 单层表现出低剥离能 (0.84 J/m ² ) 和高机械/热稳定性，表明从块体中获得低维 BaCu 的潜力。 我们的研究结果扩展了二维电子化合物的结构和属性的空间，促进了具有过渡金属阴离子的新型二维电子化合物的发现和潜在应用。