Recent Progress on Mixed-Anion Materials for Energy Applications

Abstract

Mixed-anion compounds, in which multiple anions such as O2−, N3−, and H− are contained in the same compound, have recently attracted attention. Because mixed-anion compounds have a unique crystal structure with multiple anions coordinated to cations, materials with fundamentally new and innovative functions are expected to be developed for various chemistry and physics applications, including catalysts, batteries, and superconductors. In this Account, recent progress in the development of new mixed-anion compounds by the MEXT mixed-anion project is described, with emphasis on results related to the development of materials used as photocatalysts/photoelectrodes, phosphors, secondary battery components, conductors, and thermoelectric materials.

Computation-accelerated discovery of the K2NiF4-type oxyhydrides combing density functional theory and machine learning approach

“…Mixed-anion compounds beyond homoanionic materials impart intriguing properties by the virtual of the anionic diversity in ionic radius, electronegativities and polarizability (Kageyama et al, 2018;Kobayashi et al, 2018;Zapp et al, 2021;Maeda et al, 2022). In particular, oxyhydrides with the coexistence O 2and H − in the anion sublattice offer a superior functionality for materials design, as exemplified in electrolytes (Kobayashi et al, 2016;Takeiri et al, 2019;Matsui et al, 2020;Nawaz et al, 2020;Takeiri et al, 2022), catalysts (Kobayashi et al, 2017) and precursors for topochemical reaction (Masuda et al, 2015;Yajima et al, 2015;Mikita et al, 2016).…”

“…In particular, oxyhydrides with the coexistence O 2and H − in the anion sublattice offer a superior functionality for materials design, as exemplified in electrolytes (Kobayashi et al, 2016;Takeiri et al, 2019;Matsui et al, 2020;Nawaz et al, 2020;Takeiri et al, 2022), catalysts (Kobayashi et al, 2017) and precursors for topochemical reaction (Masuda et al, 2015;Yajima et al, 2015;Mikita et al, 2016). The lightest mass, large polarizability and high redox potential (-2.3 V) of hydride ions enable the oxyhydrides as novel energy storage and conversion materials (Kobayashi et al, 2016;Liu et al, 2019;Takeiri et al, 2019;Matsui et al, 2020;Nawaz et al, 2020;Lavén et al, 2021;Maeda et al, 2022;Takeiri et al, 2022), and the complex interplay between H − with unique electronic configurations and O 2qualifies the oxyhydrides as magnetic devices (Hayward et al, 2002;Bridges et al, 2005;Yajima et al, 2022). Thanks to the unique characteristics of hydride ions, the discovery of oxyhydrides standing for the frontier of chemistry will open an exciting chemical space serving various applications.…”

Orange Zn–Al–O–N Powder Active for Photocatalytic Water Reduction and Oxidation Synthesized from a Zn–Al Layered Double Hydroxide Using Urea as the Nitriding Agent

“…Oxynitrides, including N-doped oxides, have been attracting attention as functional materials. , Oxynitrides are typically synthesized via thermal ammonolysis of an oxide precursor at high temperatures (>1073 K). , The successful synthesis of a desired oxynitride is strongly dependent on the choice of the precursor and the synthesis conditions. Because the diffusion of N 3– ions in the crystal lattice is slow, the use of smaller-sized oxide precursors leads to more effective conversion to the corresponding oxynitrides. − Thermal ammonolysis requires a continuous flow of toxic ammonia gas; however, a solid-state nitriding agent such as urea or carbon nitride, both of which are much less toxic than ammonia, can be used as an alternative to thermal ammonolysis. − …”

“…Oxynitrides, including N-doped oxides, have been attracting attention as functional materials. 1,2 Oxynitrides are typically synthesized via thermal ammonolysis of an oxide precursor at high temperatures (>1073 K). 3,4 The successful synthesis of a desired oxynitride is strongly dependent on the choice of the precursor and the synthesis conditions.…”

A two-dimensional perovskite oxyfluoride Pb3Fe2O5F2 as a catalyst for electrochemical oxidation of water to oxygen

“…Mixed-anion compounds, in which a metal centre is coordinated to more than one anionic species, are emerging solidstate materials because of their wide variety of physical and chemical properties; these properties, however, cannot be realized in single anion counterparts. 1,2 Oxyuorides containing O 2À and F À anions in the same phase are examples of such compounds, and have been developed as conductors, [3][4][5][6] battery cathodes, 7,8 phosphors, 9,10 scintillators, 11 catalysts, 12 photocatalysts, [13][14][15] and photoelectrodes. [16][17][18][19] For applications in catalysis, oxyuorides have been shown to function as electrocatalysts for oxidation of water.…”