Evidence for Anionic Excess Electrons in a Quasi-Two-Dimensional Ca<sub>2</sub>N Electride by Angle-Resolved Photoemission Spectroscopy

Oh, Ji Seop; Kang, Chang-Jong; Kim, Ye Ji; Sinn, Soobin; Han, Mei; Chang, Young Jun; Park, Byeong‐Gyu; Kim, Sung Wng; Min, B. I.; Kim, Hyeong–Do; Noh, Tae Won

doi:10.1021/jacs.5b12668

Cited by 63 publications

(43 citation statements)

References 30 publications

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“…The surface modification is a key ingredient for stabilizing the twodimensional [Hf 2 S] 2+ •2e − electride. In contrast to previously reported two-dimensional electrides, including [Ca 2 N] + •e − and [Y 2 C] 2+ •2e − , which are extremely unstable in air due to the layered open structure that makes excess anionic electrons react with oxygen and water molecules within several minutes (24,27), the [Hf 2 S] 2+ •2e − electride is extraordinarily stable in reactive atmospheres. Both air-and water-exposed powders exhibited no distinct change in the crystal structure, exhibiting identical XRD patterns to that of the pulverized powders of the UHV-cleaved sample (Fig.…”

Section: Chemically Stable Two-dimensional Electride [Hf 2 S] 2+ •2e −contrasting

confidence: 66%

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction

et al. 2020

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Electrides have emerged as promising materials with exotic properties, such as extraordinary electron-donating ability. However, the inevitable instability of electrides, which is caused by inherent excess electrons, has hampered their widespread applications. We report that a self-passivated dihafnium sulfide electride ([Hf2S]2+∙2e−) by double amorphous layers exhibits a strong oxidation resistance in water and acid solutions, enabling a persistent electrocatalytic hydrogen evolution reaction. The naturally formed amorphous Hf2S layer on the cleaved [Hf2S]2+∙2e− surface reacts with oxygen to form an outermost amorphous HfO2 layer with ~10-nm thickness, passivating the [Hf2S]2+∙2e− electride. The excess electrons in the [Hf2S]2+∙2e− electride are transferred through the thin HfO2 passivation layer to water molecules under applied electric fields, demonstrating the first electrocatalytic reaction with excellent long-term sustainability and no degradation in performance. This self-passivation mechanism in reactive conditions can advance the development of stable electrides for energy-efficient applications.

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Section: Chemically Stable Two-dimensional Electride [Hf 2 S] 2+ •2e −contrasting

confidence: 66%

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction

et al. 2020

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“…The seminal example is the layered dicalcium nitride (Ca 2 N) with an Anti-CdCl 2 structure (R-3m), which can be taken as [Ca 2 N] + (e -). Remarkably, the excess electrons from counting oxidation numbers were confined in the space between the [Ca 2 N] + layers, forming dense twodimensional (2D) electron layer, 6,21 promising for electron dopant, [22][23][24][25][26] batteries, 27,28 and plasmonic device applications. [29][30][31] Meanwhile, monolayer Ca 2 N preserving its unique two-dimensional electron layers in interstitial space was predicted to be stable theoretically and subsequently was grown experimentally.…”

Section: Introductionmentioning

confidence: 99%

Discovery of Hidden Classes of Layered Electrides by Extensive High-Throughput Material Screening

et al. 2019

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Despite their extraordinary properties, electrides are still a relatively unexplored class of materials with only a few compounds grown experimentally. Especially for layered electrides, the current researches mainly focus on several isostructures of Ca 2 N with similar interlayer two-dimensional (2D) anionic electrons. An extensive screening for different layered electrides is still missing. Here, by screening materials with anionic electrons for the structures in Materials Project, we uncover 12 existing materials as new layered electrides. Remarkably, these layered electrides demonstrate completely different properties from Ca 2 N. For example, unusual fully spin-polarized zero-dimensional (0D) anionic electrons are shown in metal halides with MoS 2 -like structures; unique one-dimensional (1D) anionic electrons are confined within the tubes of the quasi-1D structures; a coexistence of magnetic and non-magnetic anionic electrons is found in ZrCl-like structures and a new ternary Ba 2 LiN with both 0D and 1D anionic electrons. These materials not only significantly increase the pool of experimentally synthesizable layered electrides but also are promising to be exfoliated into advanced 2D materials. ASSOCIATED CONTENT Supporting Information.This material is available free of charge via the Internet at http://pubs.acs.org." Basic structural, electronic and magnetic properties, as well as the distribution of anionic electrons of the 12 layered electrides

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“…15,16 In recent years, Ca 2 N has been demonstrated to be an electride by electron transport measurement and since then inorganic electrides have sprung up quickly. [17][18][19][20][21] According to the dimensionality of the anionic electrons confinement, e.g., zero-dimensional (0D) cavities, one-dimensional (1D) channels and twodimensional (2D) interlayers, the electrides can be conveniently classified. A large amount of electrides with different confinement dimensionalities have been identified recently by high-throughput calculations from all known inorganic materials.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Stoner-Type Magnetism in Low-Dimensional Electrides

Sui¹,

Wang

Duan³

2019

J. Phys. Chem. C

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Electrides are special ionic solids with excess cavity-trapped electrons serving as anions. Despite the extensive studies on electrides, the interplay between electrides and magnetism is not well understood due to the lack of stable magnetic electrides, particularly the lack of inorganic magnetic electrides. Here, based on the mechanism of Stonertype magnetic instability, we propose that in certain electrides the low-dimensionality can facilitate the formation of magnetic ground state because of the enhanced density of states near the Fermi level. To be specific, A 5 B 3 (A = Ca, Sr, Ba; B = As, Sb, Bi) (1D), Sr 11 Mg 2 Si 10 (0D), Ba 7 Al 10 (0D) and Ba 4 Al 5 (0D) have been identified as stable magnetic electrides with spin-polarization energies of tens to hundreds of meV per formula unit. Especially for Ba 5 As 3 , the spin-polarization energy can reach up to 220 meV. Furthermore, we demonstrate that the magnetic moment and spin density mainly derive from the interstitial anionic electrons near the Fermi level. Our work paves a way to the searching of stable magnetic electrides and further exploration of the magnetic properties and related applications in electrides.

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Evidence for Anionic Excess Electrons in a Quasi-Two-Dimensional Ca₂N Electride by Angle-Resolved Photoemission Spectroscopy

Cited by 63 publications

References 30 publications

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction

Discovery of Hidden Classes of Layered Electrides by Extensive High-Throughput Material Screening

Prediction of Stoner-Type Magnetism in Low-Dimensional Electrides

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Evidence for Anionic Excess Electrons in a Quasi-Two-Dimensional Ca2N Electride by Angle-Resolved Photoemission Spectroscopy

Cited by 63 publications

References 30 publications

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction

Discovery of Hidden Classes of Layered Electrides by Extensive High-Throughput Material Screening

Prediction of Stoner-Type Magnetism in Low-Dimensional Electrides

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Evidence for Anionic Excess Electrons in a Quasi-Two-Dimensional Ca₂N Electride by Angle-Resolved Photoemission Spectroscopy