The emergence of Heusler alloy catalysts

Figures & data

Figure 1. Phase diagrams of (a) Al-Pt system [1] forming intermetallic compounds and (b) Fe-Pt system [2] forming ordered alloys. The diagrams were traced from National Institute for Materials Science (NIMS) AtomWork <http://crystdb.nims.go.jp/> [1,2].

Figure 2. Schematic illustration of the elemental substitution of Heusler alloys (X₂YZ) [3] and typical components of X, Y, and Z (highlighted in periodic table). Other elements such as lanthanoids and those in groups 1 and 2 are also possible components (see Ref [4]). The figure was excerpted from Ref [5], ©The Authors, some rights reserved; exclusive license American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC http://creativecommons.org/licenses/by-nc/4.0).

Figure 3. Crystal structures for (a) L2₁ (full-Heusler, Fm–3m), (b) B2 (Pm–3m), (c) A2 (bcc, Im–3m), (d) D0₃ (Fm–3m), (e) C1_b (half-Heusler, F–43m), (f) Li₂AgSb or Hg₂CuTi (inverse Heusler, F–43m), and (g) LiMgPdSn (quaternary Heusler, F–43m) phases, where symbols in parentheses represent space groups [3]. In (b), the Y and Z atoms are mixed. In (c), all atoms are mixed. In (d), X and Y elements are mixed. In (e), half of X atoms are absent, so that the structure is called a half-Heusler (XYZ) in contrast to a full-Heusler (X₂YZ), in a narrow sense. In (f), additional Y atoms occupy the vacant sites of the half-Heusler. In (g), the fourth elements (A) occupy the vacant sites of the half-Heusler. (f) and (g) show the prototype names because their Strukturbericht symbols (like L2₁) are not commonly used. For (f), there are two prototype names for the same structure.

Table 1. Heusler alloy catalysts used in the subsections 3.1 and 3.2. Top row: X, left column: Y, and cell: Z, in X₂YZ.

X Y	Fe	Co	Ni	Cu
Ti	Sn	Al, Ge, Sn	Al, Sn	Al
Mn	–	Si, Ge, Sn	Sn	–
Fe	–	Ge	–	–

Figure 4. CO conversion in CO oxidation using [1.2%CO/0.4%O₂/He balance] reactant during a continuous heating, for (a) pure X powders, (b) X₂TiSn, (c) X₂TiAl, and (d) X₂MnSn. Colors and symbols in (b–d) correspond to those in (a). Horizontal line at 66.7% is a guide for describing the maximum conversion calculated from the CO:O₂ ratio. After Ref [11], reproduced with permission by ACS, https://pubs.acs.org/doi/10.1021/acsomega.6b00299. Further permissions related to the material excerpted should be directed to the ACS.

Figure 5. CO conversion in CO oxidation using [1.2%CO/0.4%O₂/He balance] reactant during heating and cooling cycles, for (a) Fe₂TiSn, (b) Ni₂TiSn, and (c) Co₂TiSn. After Ref [11], reproduced with permission by ACS, https://pubs.acs.org/doi/10.1021/acsomega.6b00299. Further permissions related to the material excerpted should be directed to the ACS.

Figure 6. C₃H₄ conversion in C₃H₄ hydrogenation using [1%C₃H₄/55%H₂/He balance] reactant. The data was obtained during the second cooling cycle of continuous heating and cooling, in which a temporal change in conversion was well settled. After Ref [11], reproduced with permission by ACS, https://pubs.acs.org/doi/10.1021/acsomega.6b00299. Further permissions related to the material excerpted should be directed to the ACS.

Figure 7. (a–c) C₃H₄ conversion and C₃H₆ selectivity in C₃H₄ hydrogenation using [0.1%C₃H₄/40%H₂/He balance] reactant, and (d–f) C₃H₆ conversion in C₃H₆ hydrogenation using [0.1%C₃H₆/40%H₂/He balance] reactant, for (a,d) Co₂MnGe, (b,e) Co₂FeGe, and (c,f) Co₂FeGa_0.75Ge_0.25 catalysts. The figure was remade using the data in Ref [5], ©The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC, http://creativecommons.org/licenses/by-nc/4.0).

Figure 8. Alkyne conversions and alkene selectivities in alkyne hydrogenations in the presence of alkenes for (a) Co₂MnGe, (b) Co₂FeGe, and (c) Co₂FeGa. The reactant was [0.1%C₃H₄ or C₂H₂/10%C₃H₄ or C₂H₄/40%H₂/He balance]. After Ref [5], © The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC, http://creativecommons.org/licenses/by-nc/4.0).

Figure 9. Elemental substitution effects on (a) C₃H₄ reaction rate at 50 °C and C₃H₆ selectivity at 200 °C, and (b) experimental E_a and calculated ε_d in Mn substitution (Co₂Mn_xFe_1–xGe) and Ga substitution (Co₂FeGa_yGe_1–y) for Co₂FeGe. The rate is per surface area and relative to that of Co₂FeGe. The figure was remade using the data in Ref [5], ©The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC, http://creativecommons.org/licenses/by-nc/4.0).

Figure 10. (a) Schematic illustrations of (110) surfaces, and (b) local partial DOS (LPDOS) of Ga 4p and Ge 4p bands at Co₂FeGa(110) and Co₂FeGe(110) surfaces, respectively. The figure was excerpted from Ref [5], ©The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC, http://creativecommons.org/licenses/by-nc/4.0).

Table 2. List of Heusler catalysts with preparation conditions, including phases indicated by XRD and catalytic properties in Ref [14]. ‘Up’ and ‘Down’ for Knoevenagel condensation means that activity was higher or lower than that for SiO₂ support without Heusler catalysts, respectively. Phases in samples 14–17 were not determined (n.d.).

No.	Alloy	Support	Solvent	Annealing atmosphere	XRD	Activity for Knoevenagel condensation	Selective reduction of NO
1	Co2FeGa	SiO2	Methanol	H2	A2 + A1	Down	–
2	Co2FeAl	SiO2	Methanol	H2	A2 + A1	Up	–
3	Co2FeSi	SiO2	Methanol	H2	A2 + A1	Down	–
4	Co2FeIn	SiO2	Methanol	H2	A2 + little A1	Down	–
5	Co2FeGa	SiO2	Water	H2	A2 + A1	Down	–
6	Co2FeAl	SiO2	Water	H2	A2 + little A1	Up	–
7	Co2FeSi	SiO2	Water	H2	A2 + little A1	Up	–
8	Co2FeGa	SiO2	Water	5%H2/N2	A2 + A1	Up	–
9	Co2FeAl	SiO2	Water	5%H2/N2	A2 + A1	Up	–
10	Co2FeSi	SiO2	Water	5%H2/N2	A2 + little A1	Down	–
11	Co2FeIn	SiO2	Methanol	5%H2/N2	A2 + little A1	Probably down	–
12	Cu2FeAl	SiO2	Water	5%H2/N2	A1	–	Moderately active, N2O produced
13	Cu2FeSi	SiO2	Water	5%H2/N2	A1	–	Moderately active, N2O produced
14	Fe2MnGa	Al2O3	Water	10%H2/N2	n.d.	–	Highly active, no N2O
15	Fe2MnSi	Al2O3	Water	10%H2/N2	n.d.	–	Highly active, no N2O
16	Co2CuAl	Al2O3	Water	10%H2/N2	n.d.	–	Highly active, no N2O
17	Fe2TiGa	Al2O3	Water	10%H2/N2	n.d.	–	Highly active, no N2O

Figure 11. Size distribution for (a) smaller particles (mainly < 400 nm) and (b) larger particles (mainly > 400 nm) in Sample 8 listed in Table 2. The figure was excerpted from Ref [14]. with slight rearrangement. See Ref [14]. for details of how to estimate the minimum diameter.

Massalski TB, Okamoto H, Subramanian PR, Kacprzak L, editors. Binary alloy phase diagrams. Vol. 1, 2nd. Materials Park (OH): ASM International; 1990. p. 195–197.

 Google Scholar

Massalski TB, Okamoto H, Subramanian PR, Kacprzak L, editors. Binary alloy phase diagrams. Vol. 2, 2nd. Materials Park (OH): ASM International; 1990. p. 1752–1756.

 Google Scholar

Momma K, Izumi F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J Appl Crystallogr. 2011;44(6):1272–1276.

 Web of Science ®Google Scholar

Yin M, Hasier J, Nash P. A review of phase equilibria in Heusler alloy systems containing Fe, Co or Ni. J Mater Sci. 2016;51(1):50–70.

 Web of Science ®Google Scholar

Kojima T, Kameoka S, Fujii S, et al. Catalysis-tunable Heusler alloys in selective hydrogenation of alkynes: a new potential for old materials. Sci Adv. 2018;4(10):eaat6063.

 PubMed Web of Science ®Google Scholar

Kojima T, Kameoka S, Tsai A-P. Heusler alloys: a group of novel catalysts. ACS Omega. 2017;2(1):147–153.

 PubMed Web of Science ®Google Scholar

Mueller U, Sundermann A, Trukhan N, et al., inventor; BASF, SE, assignee. Ternary intermetallic compound catalyst. United States patent US 2018/0243691 A1. 2018 Aug 30.

 Google Scholar