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Rafat Tahawy, Salma Aridha Muflihah, Kosuke Hara, Tatsuhiko Ohto, Hisanori Tanimoto, Tianshu Li, Mahmoud Abdelnabi, Samuel Jeong, Tomohiko Nishiuchi, Hajime Kimizuka, Akfiny Hasdi Aimon, Yoshikazu Ito

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[Catalyst poisoning influences from various functional groups of energy carriers towards electrochemical oxidation reactions on non-noble high entropy alloy anodes in acidic media](https://mdr.nims.go.jp/datasets/6c039902-55b4-417f-a8a0-3896c64c44cc)

## Fulltext

Microsoft Word - tsta_a_2653417_sm8360.docx Information Classification: GeneralSupplementary material  Catalyst poisoning influences from various functional groups of energy carriers towards electrochemical oxidation reactions on non-noble high entropy alloy anodes in acidic media Rafat Tahawya,b, Salma Aridha Muflihaha,c,†, Kosuke Harad,†, Tatsuhiko Ohtod,*, Hisanori Tanimotoa, Tianshu Lia, Mahmoud Abdelnabia,e, Samuel Jeonga, Tomohiko Nishiuchif, Hajime Kimizukad, Akfiny Hasdi Aimonc,g, Yoshikazu Itoa,h,* aDepartment of Applied Physics, Institute of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan bCentral Metallurgical Research and Development Institute (CMRDI), P.O. Box 87 Helwan, 11421, Egypt cDepartment of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, 40132, Indonesia dGraduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan ePhysics Department, Faculty of Science, Ain Shams University, Cairo 11566, Egypt  fDepartment of Chemistry, Graduate School of Science, The University of Osaka, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan gCollaboration Research Center for Advanced Energy Materials, National Research and Innovation Agency, Institut Teknologi Bandung, Bandung, 40132, Indonesia hTsukuba Institute for Advanced Research (TIAR), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan *Corresponding Author Yoshikazu Ito; Email: ito.yoshikazu.ga@u.tsukuba.ac.jp Tatsuhiko Ohto; Email: ohto@nagoya-u.jp †Equal contribution   Information Classification: GeneralSupplementary discussion Our research target is the concentrations of crossover molecules in the counter chamber and the target concentrations of X-molecule were roughly estimated by the crossover flux quantity using the report [S1].  The crossover current density (𝑗 ) was estimated by  𝑗 = 𝑀 𝑁 𝐹  where Mfuel is the molar flux of fuel crossover (based on a CO2 detector signal), Ne is the number of electrons per molecule of fuel that are transferred in the fuel cell's preferred electrochemical reaction, and F is the Faraday constant. For formic acid and methanol, the values of Ne are 2 and 6, respectively. Thus, the Mfuel can be estimated when we determine the 𝑗  with gas chromatography method for detecting CO2 emitted from the fuel cell. Assuming that the volume containing crossovered molecules at the cathode side (i.e. an intentionally overestimated 0.1 cm thickness water layer from Nafion membrane) is 0.1 mL per MEA area (cm2), the estimated crossover molar concentrations of fuel molecules between the Nafion membrane (cathode side) and carbon paper (facing to the Nafion) exceed 0.5 M (see the table). Thus, we set the 0.5 M concentration for initial understanding of crossover characters of X-molecules in our manuscript.   Crossover current 𝑀  (mmol/cm2/h) Fuel concentration (mol/L) after 1 hour operation near the Nafion membrane 10 mA/cm2 formic acid 0.187 1.87 M 10 mA/cm2 methanol 0.062 0.62 M 10 mA/cm2 formic acid 1.87 18.7 M 10 mA/cm2 methanol 0.62 6.2 M     Information Classification: GeneralSupplementary Figures   Figure S1. A photograph of a 9eHEA sheet.   Figure S2. XRD spectra of 9eHEA sheet.   Information Classification: General0 200 400 600 800 10000100000200000300000400000500000Intensity (count)Binding energy (eV)Survey 9eHEA-1  Figure S3. XPS spectra of as-prepared 9eHEA sheet. Some of metals were oxidized under air.    Information Classification: General 40 80 120 160 2000.000.050.100.150.200.250.300.35Current density (mA cm-2)Scan rate (mV s-1) no X-molecule  ethylene glycol urea  methanol ethanol  formic acid acetaldehyde  glycerol  formaldehyde  biurea lactic acid (l) Figure S4. Cyclic voltammogram of 9eHEA anode in non-faradaic region of X-molecules such as (a) acetaldehyde, (b) biurea, (c) ethanol, (d) ethylene glycol, (e) formaldehyde, (f) formic acid, (g) glycerol, (h) no X-molecules, (i) lactic acid, (j) methanol and (k) urea with (l) the plot.  Information Classification: General0 200 400 600 800 10000150300450 lactic acid  ethanol   ethylene g lycol  methanol  formaldehyde  aceta ldehy de biurea  urea  form ic acid  no X-m olecule  glycerol-Im(Z)/OhmRe(Z)/Ohm0.5 M H2 SO4at 1.8 V (vs. RHE) Figure S5. Electrochemical impedance spectroscopy of 9eHEA anode in 0.5 M H2SO4 electrolyte containing X-molecules or no X-molecule.   Information Classification: General0 600 1200 1800 2400 3000 3600050100150200250Current Density (mA cm-2)Time (s) Acetaldehyde  Ethylene glycol Methanol  Urea Ethanol  Formic acid Biurea  Lactic acid Formaldehyde  Glycerol Figure S6. 1 h CA measurements of 9eHEA anode in 0.5 M H2SO4 electrolyte containing X-molecules for FT-IR measurements. The current density trends in Figure S6 were not matched with those in Figure 2(a) due to the use of different 9eHEA batch samples (the sample in Figure 2(a) was broken during FT-IR setup so that the different batch samples were employed for Figure S6).  4000 3500 3000 2500 2000 1500 1000 500Transmittance (arb.u)Wavenumber (cm-1) Urea Lactic acid Formic acid Formaldehyde Ethylene glycol Biurea Methanol Glycerol Ethanol Acetaldehyde Figure S7. FT-IR results on the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing X-molecules from 1 h CA measurements.    Information Classification: General280 285 290 295Intensity (arb. u)Binding energy (eV)9eHEA with glycerol raw C-C, C-H C-O totalCarbon 48.4 at.%(a)C 1s525 530 535 540Intensity (arb. u)Binding energy (eV)9eHEA with glycerol raw Oxides? -OH, C=O H2O, C-O total(b)O 1s280 285 290 295Intensity (arb. u)Binding energy (eV)9eHEA with urea raw C-C, C-H C-O COO totalCarbon: 32.3 at.%Nitrogen: 10.0  at.%(c)C 1s525 530 535 540Intensity (arb. u)Binding energy (eV)9eHEA with urea raw Oxides? C=O H2O, C-O total(d)O 1s 395 400 405 410N 1sIntensity (arb. u)Binding energy (eV)9eHEA with urea raw C-N N-H totalCarbon: 32.3 at.%Nitrogen: 10.0  at.%(e) Figure S8. XPS spectra of 9eHEA sheet after the CA test with (a-b) glycerol (C: 48.4 at.%, O: 29.1 at.% in total) and (c-e) urea (C: 32.3 at.%, O: 39.0 at.%, N: 10.0 at.% in total). The 9eHEA elements were not clearly detected due to the polymer influences.    Information Classification: General Figure S9. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte without X-molecule from 1 h CA measurements.    Figure S10. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing acetaldehyde from 1 h CA measurements.    Figure S11. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing biurea from 1 h CA measurements.   Information Classification: General Figure S12. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing ethylene glycol from 1 h CA measurements.    Figure S13. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing ethanol from 1 h CA measurements.    Figure S14. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing formaldehyde from 1 h CA measurements.   Information Classification: General Figure S15. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing formic acid from 1 h CA measurements.    Figure S16. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing glycerol from 1 h CA measurements.    Figure S17. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing methanol from 1 h CA measurements.   Information Classification: General Figure S18. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing lactic acid from 1 h CA measurements.    Figure S19. SEM-EDS mapping of the surface of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing urea from 1 h CA measurements.     Information Classification: General Figure S20. ICP-OES analysis of electrolyte in anode from the CA test with and without toluene. The leaching amount increased by 5-15% in the existence of toluene [S2].    Information Classification: General Figure S21. Voronoi tessellation. (a) Bulk structures of 9eHEA just before cutting the surface. Ni and Nb considered as active sites were indicated. (b) Voronoi tessellation of (a). (c) Fraction of the clusters for each atom. To investigate the local atomic environments of the active sites, we additionally performed the Voronoi tessellation for the bulk system just before cutting the surface [S3]. The bulk system in (a) was one of the structures annealed from 3000 K with the aid of machine-learning force field as previously reported [S4], whose simulated annealing processes can simulate as many phases appeared in the real crystal as possible. A Voronoi polyhedron is defined by Schläfli’s notation, 〈n3, n4, n5, n6〉, where ni is the number of i-edged faces of a polyhedron. The Voronoi indices of standard BCC, FCC, and icosahedral (ICOS) are 〈0, 6, 0, 8〉, 〈0, 12, 0, 0〉, and 〈0, 0, 12, 0〉, respectively [S3]. The cluster consists of FCC and ICOS, while BCC (not shown here) also exists in other six bulk structures in our calculations. The target Ni and Nb were mainly involved in ICOS. This indicates that  Information Classification: Generalthe active sites exist in other phases except BCC and FCC, or the interface between phases and glass structure.    Information Classification: General  Figure S22. DFT calculation models of oxidized 9eHEA surface. (a) Ni-centered and (b) Nb-cantered structural outline. Both models are same.    Information Classification: General Figure S23. DFT calculations of glycerol adsorption (a) on Ni with single −OH (edge) and Nb with single −OH (center) as a bridge, (b) on Nb with double −OH (edge, center), (c) on Ni with double −OH and Nb with single −OH as a bridge, (d) on Nb with double −OH (edge, center), (e) on Ni with single −OH (edge) and (f) on Ni with single −OH (center) on the oxidized 9eHEA surface.     Information Classification: General Figure S24. DFT calculations of urea adsorption (a) on Ni with −NH2 at a parallel position, (b) on Ni with −NH2 at a perpendicular position, (c) on Ni with C=O at a parallel position and (d) on Ni with C=O at a perpendicular position on the oxidized 9eHEA surface.     Information Classification: General Figure S25. DFT calculations of urea adsorption (a) on Nb with −NH2 at a parallel position, (b) on Nb with −NH2 at a perpendicular position, (c) on Nb with C=O at a parallel position and (d) on Nb with C=O at a perpendicular position on the oxidized 9eHEA surface.     Information Classification: GeneralTable S1. Summary of electrochemical performance of 9eHEA anode tested in 0.5 M H2SO4 electrolyte containing X-molecules and no X-molecule.  η10 (V) η100 (V) Tafel slope (mV/dec) Cdl (mF/cm2) Rct (Ohm) No molecule 0.72 0.86 126 22.0 861 Methanol 0.70 0.85 125 22.4 590 Ethanol 0.71 0.87 126 26.4 620 Ethylene glycol 0.74 0.97 122 34.7 555 Glycerol  0.68 0.83 122 26.1 450 Formaldehyde  0.70 0.84 134 32.0 458 Acetaldehyde 0.70 0.86 133 21.2 760 Formic acid 0.71 0.87 134 24.9 590 Lactic acid 0.71 0.84 130 37.5 640 Urea  0.72 - 175 22.4 928 Biurea  0.68 0.85 156 33.8 780     Information Classification: GeneralTable S2. Summary of atomic concentrations of 9eHEA anode before and after the test with and without X-molecules. 9eHEA with X-molecules after the CA test Atomic concentration (at.%) Ti Cr Mn Fe Co Ni Zr Nb Mo acetaldehyde 10.6 12.8 11.0 12.8 11.8 11.1 10.7 11.5 7.9 biurea 9.9 13.2 10.8 12.7 11.5 10.2 10.2 11.7 9.9 ethylene glycol 7.8 12.0 6.5 11.6 9.6 7.4 9.8 13.3 22.0 ethanol 8.5 14.0 5.3 12.7 10.7 6.9 9.0 13.9 18.9 formaldehyde 11.0 11.5 9.2 10.5 9.0 8.0 11.9 14.1 14.7 formic acid 8.3 10.9 8.8 10.4 8.8 7.2 8.3 19.5 17.7 glycerol 8.2 14.9 12.5 13.7 10.5 7.4 9.6 12.5 10.8 methanol 9.2 13.7 3.2 13.1 10.6 8.1 9.8 13.5 19.0 lactic acid 8.4 13.8 10.5 12.7 10.6 8.5 9.7 12.2 13.5 urea 9.9 8.6 7.8 8.9 8.9 9.0 9.5 22.1 15.3 9eHEA without X-molecules Atomic concentration (at.%) Ti Cr Mn Fe Co Ni Zr Nb Mo as-synthesized 10.8 11.0 8.3 11.6 12.3 11.8 10.9 11.4 11.9 after test 11.9 8.9 3.9 7.44 7.94 6.78 11.0 21.1 21.0     Information Classification: GeneralReferences [S1] Jeong KJ, Miesse CM, Choi JH, et al. Fuel crossover in direct formic acid fuel cells, Journal of Power Sources. 2027;168:119–125. doi: 10.1016/j.jpowsour.2007.02.062 [S2] Tajuddin AAH, Ohto T, Tanimoto H, et al. Toluene-Poisoning-Resistant High-Entropy Non-Noble Metal Anode for Direct One-Step Hydrogenation of Toluene to Methylcyclohexane. ChemSusChem. 2025;18(2):e202401071. doi: 10.1002/cssc.202401071 [S3] Zhou W, Song J, Lin L, et al, npj Computational Materials, 2025;11:69. doi: 10.1038/s41524-025-01561-1 [S4] Tajuddin AAH, Wakisaka M, Ohto T, et al. Corrosion-Resistant and High-Entropic Non-Noble-Metal Electrodes for Oxygen Evolution in Acidic Media. Advanced Materials. 2023;35(3):2207466. doi: 10.1002/adma.202207466