Nonequilibrium Flow-Synthesis of Immiscible Binary and High-Entropy Alloy Nanoparticles and Investigation of Their Catalytic Properties and Electronic Structures

When and Where

Dec 1, 2022
8:45am - 9:00am

Hynes, Level 2, Room 202

Presenter

Kohei Kusada

Dongshuang Wu

Tomokazu Yamamoto

Takaaki Toriyama

Syo Matsumura

Yusuke Nanba

Michihisa Koyama

Okkyun Seo

Osami Sakata

Hiroshi Kitagawa

Co-Author(s)

Kohei Kusada^1,2,Dongshuang Wu¹,Tomokazu Yamamoto³,Takaaki Toriyama³,Syo Matsumura³,Yusuke Nanba⁴,Michihisa Koyama⁴,Okkyun Seo⁵,Osami Sakata⁵,Hiroshi Kitagawa¹

Kyoto University¹,JST-PRESTO²,Kyushu University³,Shinshu University⁴,JASRI⁵

Abstract

Kohei Kusada^1,2,Dongshuang Wu¹,Tomokazu Yamamoto³,Takaaki Toriyama³,Syo Matsumura³,Yusuke Nanba⁴,Michihisa Koyama⁴,Okkyun Seo⁵,Osami Sakata⁵,Hiroshi Kitagawa¹

Kyoto University¹,JST-PRESTO²,Kyushu University³,Shinshu University⁴,JASRI⁵

Solid-solution alloy nanoparticles (NPs), where the constituents mix at the atomic level, show a variety of attractive properties due to their tunable electronic structures. However, the majority of bulk alloy systems are phase-separated types under ambient conditions. We have demonstrated that the nanosize effect offers a chance to find a way out of this metallurgical difficulty; that is, we can obtain metal NPs having new phases that do not exist in bulk states1-9. As one of the examples, we successfully synthesized PdRu solid-solution alloy NPs, although Ru and Pd are immiscible elements. The Pd0.5Ru0.5 NPs having a similar electronic structure to Rh exhibit comparable NOx reduction activity, even though monometallic Ru or Pd NPs do not show high activity.4, 8 Also, very recently we first synthesized high-entropy alloy NPs composed of all eight noble-metal-group elements (NM-HEA NPs) and revealed that the local density of states (LDOS) of every surface atom in NM-HEA are different.9 Some atoms of the same constituent element in HEA NPs have different LDOS profiles, whereas atoms of other elements can have similar LDOS profiles. In other words, one atom in HEA loses its elemental identity and it may be possible to create an ideal LDOS by adjusting the neighboring atoms. The NM-HEA NPs showed 10.8-times higher activity for hydrogen evolution reaction than commercial Pt/C, which is one of the best catalysts. However, it is still difficult to stably synthesize solid-solution alloy NPs, particularly nonequilibrium alloys that consist of combinations immiscible in the bulk. We first developed a continuous-flow reactor providing high productivity with high reproducibility of solid-solution alloy NPs composed of immiscible combinations and multi-elements.9 The designed solvothermal flow reactor enabled us to use lower alcohol as a reductant that cannot be applied in a batch synthesis for these NPs. 1) K. Kusada, H. Kitagawa. Adv. Mater., 2016, 28, 1129. 2) K. Kusada, et al. J. Am. Chem. Soc., 2010, 132, 15896. 3) K. Kusada, et al. J. Am. Chem. Soc., 2013, 135, 5403. 4) K. Kusada, et al. J. Am. Chem. Soc., 2014, 136, 1864. 5) Q. Zhang et al., Nat. Commun., 2018, 9, 510. 6) K. Kusada et al., Chem. Sci., 2019, 10, 652. 7) D. Wu. et al. J. Am. Chem. Soc., 2020, 142, 13833. 8) K. Kusada, et al., Adv. Mater., 2021, 33, 2005206. 9) D. Wu. et al. J. Am. Chem. Soc., 2022, 144, 3365. 10) K. Kusada, et al., J. Phys. Chem. C, 2021, 125, 458.