Room‐Temperature Synthesis of High‐Entropy Perovskite Oxide Nanoparticle Catalysts through Ultrasonication‐Based Method

Abstract

In the present study,asonochemical-based method for onepot synthesis of entropy-stabilized perovskite oxide nanoparticle catalysts with high surface area was developed. The highentropyp erovskite oxidesw ere synthesized as monodispersed, spherical nanoparticles with an average crystallite sizeo fa pproximately 5.9 nm. Ta king advantage of the acoustic cavitation phenomenon in theu ltrasonication process, BaSr(ZrHf-Ti)O 3 ,B aSrBi(ZrHfTiFe)O 3 and Ru/BaSrBi(ZrHfTiFe)O 3 nanoparticles were crystallized as single-phase perovskite structures through ultrasonication exposure withoutc alcination. Notably, the entropically-driven stability of Ru/BaSrBi(ZrHfTiFe)O 3 with excellent dispersion of Ru in the perovskite phase bestowed the nanoparticles of Ru/BaSrBi(ZrHfTiFe)O 3 with good catalytic activity for CO oxidation.As ignificant breakthrough in multicomponent alloy systems has inspired the exploration of the vast compositional space offered by high-entropy materials (HEMs). [1][2][3][4][5][6] HEMs are based on the premise of incorporatingm ultiple components (usually five or more) into as ingle crystal phase to attain unique combination of properties that are otherwise unattainable in conventional solid solutions. [7] Amongt his novel class of crystalline materials, high-entropy alloys were first reported in 2004 by the independentp ioneering works of Cantor et al. and Yeh et al. [5,6] Recent studies have extended the high-entropy concept to include the ionic compounds, in which five or more metallice lements have been used to populate as inglec ation sublattice to introduce highc onfigurational entropyi nto the crystal structure. Examples include high-entropy metal dibor-ides, [4] high-entropy nitrides, [8,9] and high-entropy metal oxides (HEMOs). [10] More recently,J iang et al. extended the HEMO study to include perovskite-type oxides with six and seven metallice lements. [11] The synthesis involved blending and ball millingo fs toichiometric amounts of the corresponding metaloxide precursors for approximately 6h and subsequentc alcination at temperatures above 1300 8Ct of orm the high-entropy perovskite oxide (HEPO) ceramics. Although the particle size distribution of the synthesized perovskites was not reported, several studies have demonstrated that such extreme temperatured uring the synthetic process causes coagulation of grain boundaries, leadingt ot he formation of clumps, and consequent reduction in the available surfacea rea for reactions. [10,12,13] Although conventional perovskites with high-surface area have been synthesized previously, [14,15] high-entropy perovskites with high surfacearea have not been reported previously to the best of our knowledge.Perovskites are an important class of materials that exhibit a wide range of functionality,m aking them desirable for use in different areas of application including heterogenous catalysis. [16] In 1975, Gallagher et al. reported the use of perovskites as potentialr eplacement for noble-metal-based catalystsi na utomotive exhaust systems. [17] The initia...

High-entropy ceramics: Present status, challenges, and a look forward

“…Besides theoretical impact, the advent of HECs also poses challenges on the synthesis and densification of this new family of materials. In order to obtain random distribution of constituting elements in HECs, various methods including solid state reaction [32,58,85,99,101,[109][110][111], wet chemical route [37,60,[63][64][65]91,93], solidification [112][113][114], field assisted synthesis [115,116], and epitaxial growth [117] have been used.…”

Across the Board: Sheng Dai on Catalyst Design by Entropic Factors

“…[6] More recently,t he sonochemical methodb ased on ultrasonication was also extended to synthesize high-entropy perovskite oxide materials with enhanced surfacea rea for catalysis. [9] In addition, am echanochemicals ynthesis methodology was developed to obtain porous high-entropyo xide materials for catalysis. [10] Sheng Dai obtained his B.S.…”

“…There are severalr eports on enhanced catalysis performances by HEMs. [9,11] However,n o detailedm echanistic elucidations have been given.Af inal question is,c an HEMs be used as an ideal catalyst support to disperse SACs? [12]…”

“…The advantage of this class of SACs involving Pt species was clearly demonstrated with the CO oxidation reaction as a probe reaction (Figure ) . More recently, the sonochemical method based on ultrasonication was also extended to synthesize high‐entropy perovskite oxide materials with enhanced surface area for catalysis . In addition, a mechanochemical synthesis methodology was developed to obtain porous high‐entropy oxide materials for catalysis …”

“…Another exciting research area will be the fundamental investigation of the cooperative and synergistic effects caused by multicomponent HEMs in catalysis. There are several reports on enhanced catalysis performances by HEMs . However, no detailed mechanistic elucidations have been given.…”