Mixed hydride-electronic conductivity in Rb2CaH4 and Cs2CaH4

Hendrik P. Rodenburg; Alexander Mutschke; Lappawat Ngamwongwan; Valerio Gulino; Vasileios Kyriakou; Nathalie Kunkel; Nongnuch Artrith; Peter Ngene

doi:10.1016/j.ssi.2023.116384

Mixed hydride-electronic conductivity in Rb₂CaH₄ and Cs₂CaH₄

Hendrik P. Rodenburg
, Alexander Mutschke
, Lappawat Ngamwongwan
, Valerio Gulino
, Vasileios Kyriakou
, Nathalie Kunkel
, Nongnuch Artrith
, Peter Ngene^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Hydride-ion conductors and mixed hydride-electronic conductors are promising materials for various applications, especially in (electro)chemical energy conversion and storage. Many of the hydride-ion conductors discovered to date are oxyhydrides with the K₂NiF₄-type structure. In this work, Cs₂CaH₄ and Rb₂CaH₄, which crystallize in the K₂NiF₄-type structure, were synthesized and electrochemically characterized. By employing electrochemical impedance spectroscopy (EIS) and single-step chronoamperometry measurements, it is found that both materials show mixed ionic-electronic conductivity at moderate (100–200 °C) temperatures. The overall conductivity of both materials is increased by the release of hydrogen at elevated temperatures, indicating an effect of hydride vacancy concentration on the conductivity. This suggests that the ionic conductivity is due to hydride-ion transport, which is further supported by Climbing Imaged Nudged Elastic Band (CINEB) calculations. Cs₂CaH₄ shows approximately equal ionic and electronic conductivity at 190 °C (total conductivity σ = 2.1 × 10⁻⁶ S cm⁻¹), while Rb₂CaH₄ (σ = 8.8 × 10⁻⁷ S cm⁻¹ at 190 °C) is primarily an ionic conductor. As mixed hydride-electronic conductors, both materials show promise in chemical conversion and energy conversion applications.

Original language	English
Article number	116384
Journal	Solid State Ionics
Volume	403
DOIs	https://doi.org/10.1016/j.ssi.2023.116384
Publication status	Published - 15 Dec 2023

Bibliographical note

Publisher Copyright:
© 2023 The Author(s)

Funding

HR, VG and PN thank Laura de Kort for helpful discussions and LN and NA thank Maris Rokhline for valuable discussions. HR and PN thank Utrecht University for funding the experimental work. LN and NA thank the Dutch national e-infrastructure and the SURF Cooperative for computational resources that were used for the DFT simulations. LN thanks the Development and Promotion of Science and Technology Talents (DPST) Project Thailand for financial support. AM and NK thank the DFG for funding (project number 245845833 ) within International Research Training Group IRTG 2022—Alberta Technical University of Munich School for Functional Hybrid Materials (ATUMS) . HR, VG and PN thank Laura de Kort for helpful discussions and LN and NA thank Maris Rokhline for valuable discussions. HR and PN thank Utrecht University for funding the experimental work. LN and NA thank the Dutch national e-infrastructure and the SURF Cooperative for computational resources that were used for the DFT simulations. LN thanks the Development and Promotion of Science and Technology Talents (DPST) Project Thailand for financial support. AM and NK thank the DFG for funding (project number 245845833) within International Research Training Group IRTG 2022—Alberta Technical University of Munich School for Functional Hybrid Materials (ATUMS).

Funders	Funder number
ATUMS
Alberta Technical University of Munich School for Functional Hybrid Materials
Development and Promotion of Science and Technology Talents
SURF
the Deutsche Forschungsgemeinschaft	245845833
Universiteit Utrecht

Keywords

Hydride ions
Hydride-ion conductivity
Ionic conduction
Metal hydrides
Mixed ionic-electronic conductivity

Access to Document

10.1016/j.ssi.2023.116384Licence: CC BY

1-s2.0-S0167273823002424-mainFinal published version, 4.68 MBLicence: CC BY

Cite this

@article{f5db1261bfeb47fd81369803cd9fea38,

title = "Mixed hydride-electronic conductivity in Rb2CaH4 and Cs2CaH4",

abstract = "Hydride-ion conductors and mixed hydride-electronic conductors are promising materials for various applications, especially in (electro)chemical energy conversion and storage. Many of the hydride-ion conductors discovered to date are oxyhydrides with the K2NiF4-type structure. In this work, Cs2CaH4 and Rb2CaH4, which crystallize in the K2NiF4-type structure, were synthesized and electrochemically characterized. By employing electrochemical impedance spectroscopy (EIS) and single-step chronoamperometry measurements, it is found that both materials show mixed ionic-electronic conductivity at moderate (100–200 °C) temperatures. The overall conductivity of both materials is increased by the release of hydrogen at elevated temperatures, indicating an effect of hydride vacancy concentration on the conductivity. This suggests that the ionic conductivity is due to hydride-ion transport, which is further supported by Climbing Imaged Nudged Elastic Band (CINEB) calculations. Cs2CaH4 shows approximately equal ionic and electronic conductivity at 190 °C (total conductivity σ = 2.1 × 10−6 S cm−1), while Rb2CaH4 (σ = 8.8 × 10−7 S cm−1 at 190 °C) is primarily an ionic conductor. As mixed hydride-electronic conductors, both materials show promise in chemical conversion and energy conversion applications.",

keywords = "Hydride ions, Hydride-ion conductivity, Ionic conduction, Metal hydrides, Mixed ionic-electronic conductivity",

author = "Rodenburg, \{Hendrik P.\} and Alexander Mutschke and Lappawat Ngamwongwan and Valerio Gulino and Vasileios Kyriakou and Nathalie Kunkel and Nongnuch Artrith and Peter Ngene",

note = "Publisher Copyright: {\textcopyright} 2023 The Author(s)",

year = "2023",

month = dec,

day = "15",

doi = "10.1016/j.ssi.2023.116384",

language = "English",

volume = "403",

journal = "Solid State Ionics",

issn = "0167-2738",

publisher = "Elsevier BV",

}

TY - JOUR

T1 - Mixed hydride-electronic conductivity in Rb2CaH4 and Cs2CaH4

AU - Rodenburg, Hendrik P.

AU - Mutschke, Alexander

AU - Ngamwongwan, Lappawat

AU - Gulino, Valerio

AU - Kyriakou, Vasileios

AU - Kunkel, Nathalie

AU - Artrith, Nongnuch

AU - Ngene, Peter

PY - 2023/12/15

Y1 - 2023/12/15

N2 - Hydride-ion conductors and mixed hydride-electronic conductors are promising materials for various applications, especially in (electro)chemical energy conversion and storage. Many of the hydride-ion conductors discovered to date are oxyhydrides with the K2NiF4-type structure. In this work, Cs2CaH4 and Rb2CaH4, which crystallize in the K2NiF4-type structure, were synthesized and electrochemically characterized. By employing electrochemical impedance spectroscopy (EIS) and single-step chronoamperometry measurements, it is found that both materials show mixed ionic-electronic conductivity at moderate (100–200 °C) temperatures. The overall conductivity of both materials is increased by the release of hydrogen at elevated temperatures, indicating an effect of hydride vacancy concentration on the conductivity. This suggests that the ionic conductivity is due to hydride-ion transport, which is further supported by Climbing Imaged Nudged Elastic Band (CINEB) calculations. Cs2CaH4 shows approximately equal ionic and electronic conductivity at 190 °C (total conductivity σ = 2.1 × 10−6 S cm−1), while Rb2CaH4 (σ = 8.8 × 10−7 S cm−1 at 190 °C) is primarily an ionic conductor. As mixed hydride-electronic conductors, both materials show promise in chemical conversion and energy conversion applications.

AB - Hydride-ion conductors and mixed hydride-electronic conductors are promising materials for various applications, especially in (electro)chemical energy conversion and storage. Many of the hydride-ion conductors discovered to date are oxyhydrides with the K2NiF4-type structure. In this work, Cs2CaH4 and Rb2CaH4, which crystallize in the K2NiF4-type structure, were synthesized and electrochemically characterized. By employing electrochemical impedance spectroscopy (EIS) and single-step chronoamperometry measurements, it is found that both materials show mixed ionic-electronic conductivity at moderate (100–200 °C) temperatures. The overall conductivity of both materials is increased by the release of hydrogen at elevated temperatures, indicating an effect of hydride vacancy concentration on the conductivity. This suggests that the ionic conductivity is due to hydride-ion transport, which is further supported by Climbing Imaged Nudged Elastic Band (CINEB) calculations. Cs2CaH4 shows approximately equal ionic and electronic conductivity at 190 °C (total conductivity σ = 2.1 × 10−6 S cm−1), while Rb2CaH4 (σ = 8.8 × 10−7 S cm−1 at 190 °C) is primarily an ionic conductor. As mixed hydride-electronic conductors, both materials show promise in chemical conversion and energy conversion applications.

KW - Hydride ions

KW - Hydride-ion conductivity

KW - Ionic conduction

KW - Metal hydrides

KW - Mixed ionic-electronic conductivity

UR - https://www.scopus.com/pages/publications/85175069056

U2 - 10.1016/j.ssi.2023.116384

DO - 10.1016/j.ssi.2023.116384

M3 - Article

AN - SCOPUS:85175069056

SN - 0167-2738

VL - 403

JO - Solid State Ionics

JF - Solid State Ionics

M1 - 116384

ER -