Catalyst Surface Research Division. (Prof.) Kiyotaka Asakura (Assoc. Prof.) Satoru Takakusagi (Assist Prof.) Hiroko Ariga-Miwa

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1 Catalyst Surface Research Division (Prof.) Kiyotaka Asakura (Assoc. Prof.) Satoru Takakusagi (Assist Prof.) Hiroko Ariga-Miwa

2 Long term research missions 2 Surface structure and reaction and reaction mechanisms of catalysts 1. Ni 2 P surface structure 2. well-defined Inhomogeneous surface 3. Electrode surface structure for fuel cell 4. Metal structure and activity on TiO 2 (110) (Takakusagi Clutster) Development of catalyst structure analysis methods

3 Ni 2 P It is good at hydrodesulfurization, hydrodenitrogenation, hydrodeoxygenation, electrocatalytic hydrogen evolution reaction.(1-11) In order to obtain the structure and catalysis relationship, we carried out single crystal studies on Ni 2 P. However, the surface structure is not the bulkterminated one. bulk structure P62m 3 (1) Oyama, S. T.; Lee, Y. K. J. Phys. Chem. B 2005, 109 (6), (2) d Aquino, A. I.; Danforth, S. J.; Clinkingbeard, T. R.; Ilic, B.; Pullan, L.; Reynolds, M. A.; Murray, B. D.; Bussell, M. E. J. Catal. 2016, 335, 204. (3) Liu, D.; Wang, A.; Liu, C.; Prins, R. Catal. Commun. 2016, 77, 13. (4) Oyama, S. T.; Wang, X.; Lee, Y. K.; Chun, W. J. J. Catal. 2004, 221 (2), 263. (5) Oyama, S. T.; Gott, T.; Zhao, H.; Lee, Y.-K. Catal. Today 2009, 143 (1 2), 94. (6) Bando, K. K.; Wada, T.; Miyamoto, T.; Miyazaki, K.; Takakusagi, S.; Koike, Y.; Inada, Y.; Nomura, M.; Yamaguchi, A.; Gott, T.; Oyama, S. T.; Asakura, K. J. Catal. 2012, 286, 165. (7) Bando, K. K.; Wada, T.; Miyamoto, T.; Miyazaki, K.; Takakusagi, S.; Gott, T.; Yamaguchi, A.; Nomura, M.; Oyama, S. T.; Asakura, K. In 14th International Conference on X-Ray Absorption Fine Structure (xafs14), Proceedings; DiCicco, A., Filipponi, A., Eds.; Iop Publishing Ltd: Bristol, 2009; Vol. 190, p (8) S. T. Oyama, H. Zhao, H.-J. Freund, K. Asakura, R. Włodarczyk, M. Sierka, "Unprecedented selectivity to the direct desulfurization (DDS) pathway in a highly active FeNi bimetallic phosphide catalyst", Journal of catalysis 2012, 285, 1-5. (9) Shamanaev, I. V.; Deliy, I. V.; Aleksandrov, P. V.; Gerasimov, E. Y.; Pakharukova, V. P.; Kodenev, E. G.; Ayupov, A. B.; Andreev, A. S.; Lapina, O. B.; Bukhtiyarova, G. A. RSC Adv. 2016, 6 (36), (10) Guan, Q.; Wan, F.; Han, F.; Liu, Z.; Li, W. Catal. Today 2016, 259, Part 2, 467. (11) Berenguer, A.; Sankaranarayanan, T. M.; Gómez, G.; Moreno, I.; Coronado, J. M.; Pizarro, P.; Serrano, D. P. Green Chem. 2016, 18 (7), Ni P

4 4 Ni2P single crystal structures P-terminated structure is more stable. Sputtering surface (less P surface) is recovered at low temperature(<473 K) and P-rich surface easy diffusion path.

5 Surface stabilization (removing dangling bond ) and activity 5 The dangling bond of Ni appears at Fermi level. P termination removes the dangling bond to give the low activity. H 2 does not dissociatively adsorb on Ni 2 P. Defect is necessary. H. Ariga, M. Kawashima, S. Takakusagi, K. Asakura, Chemistry Letters 2013, 42, ; Q. Yuan, H. Ariga, K. Asakura, Top. Catal. 2015, 58, /s

6 Ni2P single crystal structures 6 P-terminated structure is more stable. Sputtering surface (less P surface) is recovered at low temperature(<473 K) and P-rich surface easy diffusion path.

7 Easy P diffusion 7 Activation energy = 0.18 ev Calc by DFT(VASP) J. Contreras-Mora, H. Ariga-Miwa, S. Takusagi, C. Williams, K. Asakura, J.Phys.Chem.C. 2018, Accepted.

8 Development of catalyst structure analysis methods PTRF-XAFS PTRF-XAFS in in Poster Poster of of Prof. Prof. Takakusagi Takakusagi Highly sensitive XAFS Poster of Dr. Felix Feitne 8 Muon studies of TiO2(110) Poster of Dr. Felix Feitne Characterization methods -Accerlerator Base Characterizations Marx Raman XAFS Positron diffraction Ultrafast XAFS

9 EXAFS=Extended X-ray Absorption Fine Structure XANES EXAFS ( ev) µ/ arb. units I 0 I µ = ln ( I 0 / I ) X-ray scattering atom Photon energy/ ev X-ray Absorbing atom Element specific Structure can be revealed around X-ray absorbing atom Operando spectroscopy

10 Time-resolved XAFS 10 QXAFS =A technique that can measure one EXAFS spectrum in a short time ( a few seconds in our system) by sampling signals from ionization chambers and monochromator continuously with scanning the monochromator (on the fly). K. K. Bando, Y. Koike, T. Kawai, G. Tateno, S. T. Oyama, Y. Inada, M. Nomura, K. Asakura, Journal of Physical Chemistry C 2011, 115, /jp11657z. DXAFS =Energy dispersion is made by polychromator. The beams are focused on the sample and dispersed again to be detected by position sensitive detector to give the whole spectrum at once. (µs ) A. Yamaguchi, T. Shido, Y. Inada, T. Kogure, K. Asakura, M. Nomura, Y. Iwasawa, Bull.Chem.Soc.Jpn. 2001, 74,

11 Pump Probe XAFS setup for Photocatalyst Sample: 0.6 mm WO 3 suspension pump laser: 400 nm 270 mj/cm Hz X-ray pulse width: 100 ps(fwhm) 2p 5d J. Synchrotron Radiat. 2007, 14, 313. J. Synchrotron Radiat. 2009, 16, 110. R. Abe, et. al. J. Am. Chem. Soc. 2008, 130,

12 Photoexcited State of WO 3 : L III XANES at PF-AR Single bunch operation 1.Uemura, Y.; Uehara, H.; Niwa, Y.; Nozawa, S.; Sato, T.; Adachi, S.; Ohtani, B.; Takakusagi, S.; Asakura, K., In Situ Picosecond Xafs Study of an Excited State of Tungsten Oxide. Chem. Lett. 2014, k = 0.5(1) ns -1 The excited state decayed in 10 ns. It was successfully fitted with a single exponential function.

13 Pump probe XAFS at SACLA Experiments at SACLA SPring-8 ~30 fs SACLA ~50 fs Sample: 4 mm WO 3 suspension pump laser: 520 mj/cm Hz X-ray pulse width: 30 fs(fwhm) Time resolution: 500 fs

14 Ultra fast XAFS on WO 3 in the photoabsorption process Three distinct peaks were found in the differential spectra. peak A : Edge shift due to formation of W 5+ < 1 ps peak C : decrease of absorption from e g orbitals ~ 200 ps peak B which was not found in the previous experiments was observed. Y. Uemura, D. Kido, Y. Wakisaka, H. Uehara, T. Ohba, Y. Niwa, S. Nozawa, T. Sato, K. Ichiyanagi, R. Fukaya, S. Adachi, T. Katayama, T. Togashi, S. Owada, K. Ogawa, M. Yabashi, K. Hatada, S. Takakusa, Y. Yokoyama, B. Ohtani, K. Asakura, Angew. Chem.Int.Ed 2016, 55, /anie : Y. Uemura, H. Uehara, Y. Niwa, S. Nozawa, T. Sato, S. Adachi, B. Ohtani, S. Takakusagi, K. Asakura, Chemistry Letters 2014,

15 Problems of XAFS 15 XAFS is element specific but not bond specific. Low Z element requires low X-ray energy so that operando measurement is difficult due to the absorption of low energy x-ray by gas phase. Using the X-ray and resonance of neighboring atom, bond-specific XAFS may possible.

16 Possibility of MARX-RAMAN RAMAN XAFS is element-specific. But it is not bond-specific. Pt-C can not be distinguished from C in electrode. MARPE may be possible. 2. It is difficult to carry out in situ for Low-Z element. N, C has to be measured in soft X-ray regions. X-ray Raman can do it but low intensity.. (A. Kay, C.S. Fadley, RMultiatom resonant photoemission: a method for determining nearneighbor atomic identities and bonding. Science. 281,679(1998). ) Combination will make it possible to realize both. (K. Tohji, Y. Udagawa, Physical Review B 1987, 36, )

17 MARX-RAMAN(Multi atom resonance X-ray Raman) 17 Vaccum level X-ray Emission Resonant X-ray Raman Vaccum level Photoelectron X-ray MARX Raman Atom A Atom B. (A. Kay, C.S. Fadley, RMultiatom resonant photoemission: a method for determining nearneighbor atomic identities and bonding. Science. 281,679(1998). )

18 MARX-RAMAN of TaN. 18

19 19 Improvement of 4 D resolutions(space Energy Angle and Time) Time Resolution Special resolution Energy resolution Angle resolution Tada, M.; Ishiguro, N.; Uruga, T.; Tanida, H.; Terada, Y.; Nagamatsu, S.-i.; Iwasawa, Y.; Ohkoshi, S.-i., [Small Mu ]-Xafs of a Single Particle of a Practical Niox/Ce2zr2oy Catalyst. Phys Chem Chem Phys 2011, 13, Singh, J.; Lamberti, C.; van Bokhoven, J. A., Advanced X- Ray Absorption and Emission Spectroscopy: In Situ Catalytic Studies. Chemical Society reviews 2010, 39, Koike, Y.; Ijima, K.; Chun, W. J.; Ashima, H.; Yamamoto, T.; Fujikawa, K.; Suzuki, S.; Iwasawa, Y.; Nomura, M.; Asakura, K., Structure of Low Coverage Ni Atoms on the Tio2(110) Surface - Polarization Dependent Total-Reflection Fluorescence Exafs Study. Chem. Phys. Lett. 2006, 421,

20 Summary and future 20 Catalytic properties of Ni 2 P(0001) or (101b0) Electrochemistry and hydrogen evolution reaction. Investigations of intermetallic surfaces. Development of new techniques for characterizations with 4 D resolutions.