Reversibility limitations of metal exsolution reactions in niobium and nickel co-doped strontium titanate

Weber, Moritz L.; Sohn, Yoo Jung; Dittmann, Regina; Waser, Rainer; Menzler, Norbert H.; Guillon, Olivier; Lenser, Christian; Nemšák, Slavomír; Gunkel, Felix

doi:10.1039/d3ta02927a

Cited by 2 publications

(1 citation statement)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Exsolution has been found to take place, for instance, at temperatures of T = 1173 K within hundreds of seconds 20 (although much longer times are generally used to produce catalytic systems). The characteristic temperature−time window for cation transport processes in titanate perovskites, 21−23 however, is substantially different, as evidenced by the typical synthesis conditions for the starting solid solutions, of T > 1400 K for tens of hours 1,2,12,20,24,25 (see Figure 1). Curiously, the kinetics of reincorporation of the exsolved component under oxidizing conditions 26 are consistent with the standard (high) temperature−(long) time window.…”

Section: ■ Introductionmentioning

confidence: 99%

A Single Model for the Thermodynamics and Kinetics of Metal Exsolution from Perovskite Oxides

Bonkowski,

Wolf,

et al. 2024

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Exsolution has emerged as an outstanding route for producing oxide-supported metal nanoparticles. For ABO3-perovskite oxides, various late transition-metal cations can be substituted into the lattice under oxidizing conditions and exsolved as metal nanoparticles after reduction. A consistent and comprehensive description of the point-defect thermodynamics and kinetics of this phenomenon is lacking, however. Herein, supported by hybrid density-functional-theory calculations, we propose a single model that explains diverse experimental observations, such as why substituent transition-metal cations (but not host cations) exsolve from perovskite oxides upon reduction; why different substituent transition-metal cations exsolve under different conditions; why the metal nanoparticles are embedded in the surface; why exsolution occurs surprisingly rapidly at relatively low temperatures; and why the reincorporation of exsolved species involves far longer times and much higher temperatures. Our model’s foundation is that the substituent transition-metal cations are reduced to neutral species within the perovskite lattice as the Fermi level is shifted upward within the bandgap upon sample reduction. The calculations also indicate unconventional influences of oxygen vacancies and A-site vacancies. Our model thus provides a fundamental basis for improving existing, and creating new, exsolution-generated catalysts.

show abstract

Section: ■ Introductionmentioning

confidence: 99%

A Single Model for the Thermodynamics and Kinetics of Metal Exsolution from Perovskite Oxides

Bonkowski,

Wolf,

et al. 2024

J. Am. Chem. Soc.

View full text Add to dashboard Cite

show abstract

Synthesis and Redox Properties of Iron and Iron Oxide Nanoparticles Obtained by Exsolution from Perovskite Ferrites Promoted by Auxiliary Reactions

Filimonov,

Rozova,

Maksimov

et al. 2024

Inorganics

View full text Add to dashboard Cite

Nanoparticles of iron and iron oxides, as well as their composites, are of great scientific and technological interest. However, their properties and sustainability strongly depend on the preparation methods. Here, we present an original approach to synthesizing Fe and FeNix metal nanoparticles by exsolution, in a reducing environment at elevated temperatures from perovskite ferrites (La1−xCaxFeO3−γ, CaFeO2.5, etc.). This approach is made possible by the auxiliary reactions of non-reducible A-site cations (in ABO3 notation) with the constituents of reducing compounds (h-BN etc.). The nanoparticles exsolved by our process are embedded in oxide matrices in individual voids formed in situ. They readily undergo redox cycling at moderate temperatures, while maintaining their localization. Fe nanoparticles can be obtained initially and after redox cycling in the high-temperature γ-form at temperatures below equilibrium. Using their redox properties, a new route to producing hollow and layered oxide magnetic nanoparticles (Fe3O4, Fe3O4/La1−xCaxFeO3−γ), by separating the oxidized exsolved particles, was developed. Our approach provides greater flexibility in controlling exsolution reactions and matrix compositions, with a variety of possible starting compounds and exsolution degrees, from minimal up to ~100% (in some cases). The described strategy is highly important for the development of a wide range of new functional materials.

show abstract

Reversibility limitations of metal exsolution reactions in niobium and nickel co-doped strontium titanate

Abstract: Metal exsolution reactions enable the preparation of metal-oxide nano-composites from oxide parent materials in a single thermal reduction step. In this process, reducible metals are released from the doped oxide...

Cited by 2 publications

References 68 publications

A Single Model for the Thermodynamics and Kinetics of Metal Exsolution from Perovskite Oxides

A Single Model for the Thermodynamics and Kinetics of Metal Exsolution from Perovskite Oxides

Synthesis and Redox Properties of Iron and Iron Oxide Nanoparticles Obtained by Exsolution from Perovskite Ferrites Promoted by Auxiliary Reactions

Contact Info

Product

Resources

About