Trends and Prospects of Bimetallic Exsolution

Abstract

Supported bimetallic nanoparticles used for various chemical transformations appear to be more appealing than their monometallic counterparts, because of their unique properties mainly originating from the synergistic effects between the two different metals. Exsolution, a relatively new preparation method for supported nanoparticles, has earned increasing attention for bimetallic systems in the past decade, not only due to the high stability of the resulting nanoparticles but also for the potential to control key particle properties (size, composition, structure, morphology, etc.). In this review, we summarize the trends and advances on exsolution of bimetallic systems and provide prospects for future studies in this field.

Keywords: bimetallic exsolution; catalysis; electrochemistry; energy conversion; nanomaterials.

Figure 1

Statistic analysis on the papers published for bimetallic exsolution.

Figure 2

Schematic illustrations and energetics of alloy nanoparticle exsolution following: (a) bulk alloy formation, and (b) surface alloy formation mechanisms. (c) In situ X‐ray diffraction showing the changes of the exsolved phases on PrBaMn_1.7Co_0.1Ni_0.2O_5+δ at different temperatures. Adapted with permission. ^[11a] (d) Segregation energies of B‐site metals from LaCr_0.5Fe_0.5O₃ (LCFO) and Ni‐doped LCFO (LCFNO). Adapted with permission. ^[11d]

Figure 3

Exsolved Fe−Ni cathodes in CO₂ electrolysis. (a) Cell performance over long‐term operation at 1.3 V and 800 °C. Adapted with permission. ^[7b] (b) HRTEM image showing socketed interface between a exsolved Fe−Ni particle and a Sr₂Fe_1.35Mo_0.45Ni_0.2O_6‐δ substrate. (c) Enhanced CO₂RR performances due to exsolution of Fe−Ni nanoparticles. DFT calculations showing (d) the energies of CO₂RR over the perovskite surface and the interface between the exsolved Fe−Ni and the perovskite, and (e, f) the optimized reaction pathway at the metal‐support interface (magenta sphere and circle represent oxygen atom and vacancy involved in the reaction, respectively). Adapted with permission. ^[14]

Figure 4

Formation of Fe−Ni alloyed nanoparticles via topotactic exsolution. (a, b) Schematic comparison between conventional and topotactic exsolution, and SEM images showing the exsolved particles for each case. (c) HAADF scanning TEM with EDS of the Fe−Ni alloyed nanoparticles via topotactic exsolution. Adapted with permission. ^[20]

Figure 5

Redox stability of Fe−Co particles exsolved under different atmospheres. (a–c) Fe−Co particles freshly exsolved and (d) after 20 cycles when reduced in CO+CO₂. (e–g) Fe−Co particles freshly exsolved and (h) after 20 cycles when reduced in CO. (i, j) Schematic illustration of the interface structure during redox cycles for exsolved particles induced by CO + CO₂ and CO reduction, respectively. Adapted with permission. ^[10]

Figure 6

Exsolution of core–shell particles. (a) HRTEM, (b) HAADF, (c) EDS analysis of the exsolved core–shell Pd‐NiO particle. (d) Controlling the shell thickness of exsolved particles. Adapted with permission. ^[33]

Figure 7

Beyond bimetallic particle exsolution. (a) Fe−Co alloy with SrO exsolved. Adapted with permission. ^[39] (b) Fe/MnO_x nanoparticles. Adapted with permission. ^[41] (c) Images from left to right showing the Fe nanorod exsolved from LSF in dry H₂, the Fe−Ni alloyed particle formed on Ni–LSF in humidified H₂, and SrO nanorod grown from Ni–LSF in dry H₂, respectively. Adapted with permission. ^[43]