Supporting information. Fuel Cells Fabricated by A Selective Electrochemical Sn Deposition Method

Transcription

1 Supporting information Surface-regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by A Selective Electrochemical Sn Deposition Method Kensaku Nagasawa a, Shinobu Takao a, Shin-ichi Nagamatsu a, Gabor Samjeské a, Oki Sekizawa a, Takuma Kaneko a, Kotaro Higashi a, Takashi Yamamoto b, Tomoya Uruga a,c, and Yasuhiro Iwasawa a,d* a Innovation Research Center for Fuel Cells, The University of Electro-Communications, Chofugaoka, Chofu, Tokyo , Japan; b Faculty for Integrated Arts and Sciences, The University of Tokushima, Minamijosanjima, Tokushima , Japan; c Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo , Japan; d Graduate School of Information Science Engineering, The University of Electro-Communications, Chofugaoka, Chofu, Tokyo , Japan S

2 Figure S. Histograms of particle sizes and average particle sizes for SnO 2/Pt 3Co/C samples (Pt/Sn=4/, 9/, /, and 5/), Pt 3Co/C and Pt/C estimated from TEM images. Average size (d av): ±.7 nm. Intensity / a.u C(2) Pt 3 Co() Pt 3 Co() Pt 3 Co(2) Pt 3 Co(22) Pt 3 Co(3) 5 6 Pt() Pt(2) Pt(22) Pt(3) theta / degree Figure S2. XRD patterns for SnO 2/Pt 3Co/C (Pt/Sn=4/ (), 9/ (2), / (3) and 5/(4)), Pt 3Co/C (5) and Pt/C (6). S2

3 Intensity / a.u. (a) Pt 4f 5/2 Pt 4f 7/2 (b) Sn 3d 3/2 Sn 3d 5/2 5 Intensity / a.u Intensity / a.u Binding energy / ev Binding energy / ev Figure S3. (a) XPS spectra of Pt 4f 5/2 and 4f 7/2 levels for Pt/C (), Pt 3Co/C (2) and SnO 2/Pt 3Co/C (Pt/Sn=/ (3), Pt/Sn=9/ (4) and Pt/Sn=4/ (5)) and (b) XPS spectra of Sn 3d 3/2 and 3d 5/2 levels for SnO 2 () and SnO 2/Pt 3Co/C (Pt/Sn=/ (2), Pt/Sn=9/ (3) and Pt/Sn=4/ (4)). Pt/Sn=4/ Pt/Sn=9/ Pt/Sn=/ Pt 3 Co/C Binding energy / ev 77 Figure S4. Co 2p XPS spectra for Pt 3Co/C and SnO 2/Pt 3Co/C (Pt/Sn=/, Pt/Sn=9/ and Pt/Sn=4/). S3

4 Current density / ma cm -geo Current density / ma cm -geo Current density / ma cm -geo Current density / ma cm -geo.2. (a).2. (b) Current density / ma cm -geo cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles (c) cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles (e). Current density / ma cm -geo -. cycle cycles 2 cycles cycles 4 cycles 5 cycles (d) cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles (f) cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles Figure S5. CV curves for SnO 2/Pt 3Co/C (Pt/Sn=4/ (a), 9/ (b),/ (c) and 5/(d)), Pt 3Co/C (e) and Pt/C (f) after the aging ( cycle) and ADT cycles (, 5, cycles) at RDE in. M HClO 4. S4

5 Contrast/a.u. Contrast/a.u /nm /nm (d) Pt 3 Co()/C (c) (b) (e) c a b d Figure 3 SnO 2 /Pt 3 Co()/C Inter plane distance / nm Red Blue Figure S6. Detailed lattice contrast profiles along the red and blue arrows of Figure 5 (c), showing many defects and dislocations at the surface. S5

6 (d) (b)(c) Pt 3 Co()/C (e) (b)(c) SnO 2 /Pt 3 Co()/C Contrast nm.5.5 / nm Contrast.94 nm / =.94 nm 2 4. /nm Figure S7. Lattice contrast profiles along the red and blue arrows of Figure 5 (c) for the SnO 2/Pt 3Co/C (Pt/Sn=9/) after the aging, showing the interplane distances of.94 nm and.98 nm, which indicates the heterogeneous Pt surface arrangements with compressive strain (.94 nm) and less strain (.98 nm). S6

7 a b c (22) (22) (22) Contrast.396 nm Contrast.398 nm.396 nm.397 nm.397 nm.5 / nm.5 / nm.5 / nm A B C (22) (22) (22) Contrast.396 nm Contrast.39 nm Contrast.39 nm.5 / nm.5 / nm.5 / nm Contrast.387 nm Figure S8. HR-TEM images at three different spots for Pt 3Co/C and SnO 2/Pt 3Co/C (Pt/Sn = 9/) after the aging. (a) (c) Atomic arrangements of Pt 3Co(22) planes in the Pt 3Co/C, and lattice contrast profiles for the interplane distances along the red arrows in (a) (c), respectively. (A) (C) Atomic arrangements of Pt 3Co(22) planes in the SnO 2/Pt 3Co/C (Pt/Sn = 9/), and lattice contrast profiles for the interplane distances along the red arrows of (A) (C), respectively. Yellow arrows show typical defects and dislocations. S7

8 Current density / ma cm -geo Current density / ma cm -geo Current density / ma cm -geo (c) cycle cycles - 2 cyclrs 3 cycles 4 cycles 5 cycles (e) cycle cycles - 2 cycles 3 cycles 4 cycles 5 cycles -4-5 (a) cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles Current density / ma cm -geo Current density / ma cm -geo Current density / ma cm -geo (d) cycle cycles - 2 cycles 3 cycles 4 cycles 5 cycles -4-5 (b) cycle cycles 2 cycles 3 cycles 4 cycles 5 cycles (f) - -4 cycle cycles 2 cycles -5 3 cycles 4 cycles 5 cycles Figure S9. LSV curves at,6 rpm for the SnO 2/Pt 3Co/C catalysts with Pt/Sn=4/ (a), 9/ (b), / (c), and 5/ (d), Pt 3Co/C (e), and Pt/C (f) after the ADT 5, cycles at RDE (4.4 g-pt cm ) in. M HClO Pt/Sn=9/ 3 2 Mass activity / ma mg Pt - ECSA / m 2 g Pt Number of potential load cycles 5 4 Pt/Sn=9/ Specific activity / ma cm Pt Pt/Sn=9/ Number of potential load cycles Number of potential load cycles Figure S. ECSA, MA(mass activity) and SA(specific activity) values for SnO 2/Pt 3Co/C (Pt/Sn=9/) after the ADT, load cycles. S8

9 ECSA / m 2 g Pt Pt/Sn=3/ Pt/Sn=5/ Pt/C (TECE5E, Pt particle size 2.5 nm) Specific activity / ma cm Pt Pt/Sn=3/ Pt/Sn=5/ Pt/C (Pt particle size 2.5 nm) Number of potential load cycles Number of potential load cycles Figure S. ECSA (left) and specific activities (right) of SnO 2/Pt/C with Pt/Sn=3/ and 5/ and Pt/C (TECE5E; Pt particle size: 2.5 nm) after the ADT 5, cycles at RDE (4.4 g-pt cm ) in. M HClO 4. (A) (B) (d) Pt 3 Co()/C (d) (e) Pt 3 Co()/C SnO 2 /Pt 3 Co()/C (e) SnO 2 /Pt 3 Co()/C (d) () Pt 3 Co()/C (e) () SnO 2 /Pt 3 Co()/C Counts 4 Pt Pt 2 Sn Sn 5 Contrast/a.u nm/ =.99 nm /3 =.24 nm.989 nm/ =.99 nm nm/3=.23 nm 5-5 /nm /nm Figure S2. (A) EDS line profiles for Pt (blue) and Sn (green) along the light blue line of the TEM image for the SnO 2/Pt/C (Pt/Sn=5/). (B) Atomic arrangement of Pt() plane in TEM images of the SnO 2/Pt/C (Pt/Sn=5/), and lattice contrast profiles for the interplane distances along the red and blue arrows, showing rough surface arrangements with defects and dislocations of Pt atoms. The Pt(22) interplane distances at the surface layers and in the bulk were. and nm with a heterogeneous character, respectively, which indicates that the surface layers do not have any definite compressive strain, but there are defects and dislocations which increase the ECSA. S9

10 Contrast A B C Pt 3 Co()/C (d) (e) Pt 3 Co()/C SnO 2 /Pt 3 Co()/C (d) (e) Pt 3 Co()/C SnO 2 /Pt 3 Co()/C (e) SnO 2 /Pt 3 Co()/C Contrast / a.u. a b c.388 nm/2=.94 nm.94 nm.388 nm/2=.94 nm.39 nm/2=.95 nm.389 nm=.94 nm /nm /nm /nm Figure S3. (A) (C): Atomic arrangements for SnO 2/Pt 3Co/C (Pt/Sn = 9/) 5, cycles. (a) (b): Lattice contrast profiles for the Pt 3Co(22) interplane distances along the red arrows of (A) (C), respectively. The Ptenriched surface is compressive with many defects and dislocations. 4 2 Sn Pt Co 5 /nm Figure S4. EDS line profiles for Pt, Co and Sn in SnO 2/Pt 3Co/C (Pt/Sn = 9/) 5, cycles. S

11 Fraction / % 5 5 Pt/Sn=9/ d av =5.9 nm Fraction / % 5 5 Pt/Sn=/ d av =6.3 nm Particle size / nm Particle size / nm Fraction / % 5 5 Pt 3 Co/C d av =6.5 nm Fraction / % 5 5 Pt/C d av =7.3 nm Particle size / nm Particle size / nm Figure S5. Histograms of particle sizes and average particle sizes for SnO 2/Pt 3Co/C samples (Pt/Sn=9/ and /), Pt 3Co/C and Pt/C after the ADT 5, load cycles estimated from TEM images. Figure S6. Experimental set-up for in-situ XAFS measurements of RDE catalysts and a home-made in-situ XAFS cell. S

12 Normalized Normalized μ Normalized μ.5.5 :.4 V 2:.6 V 3:.8 V 4: V 5:.2 V 6:.4 V 7:.2 V 8: V 9:.8 V :.6 V :.4 V 6 7 White line peaks (2p 5d transition) Photon energy / ev Figure S7. In-situ Pt L III-edge XANES spectra of the SnO 2/Pt 3Co/C (Pt/Sn=/) in the series of the every.2 V stepwise increasing and decreasing potential operations between.4 V RHE and.4 V RHE at RDE in. M HClO 4. The XANES spectra under the higher potential operations than those (upto V RHE) in Figure 5 are presented here..5 SnO 2 /Pt 3 Co/C.5 Pt 3 Co/C Photon energy / ev.4 V V.4 V.5 Photon energy / ev.4 V V.4 V Figure S8. In-situ Co K-edge XANES spectra of the SnO 2/Pt 3Co/C (Pt/Sn=/) and Pt 3Co/C at.4 V RHE, V RHE and.4 V RHE in the series of the every.2 V stepwise increasing and decreasing potential operations between.4 V RHE and V RHE at RDE in. M HClO 4, corresponding to Figure. S2

13 Normalized μ Normalized μ.5 Pt L III -edge 3 2 Sn:Pt = : Pt L III -edge.5 Sn:Pt = : k 2 χ(k) /Å Photon energy / ev k / Å - Pt L III -edge Sn:Pt = :.5 Sn:Pt = 9: χ(r) /Å R / Å.5 Co K-edge 3 2 Sn:Pt = : Co K-edge Normalized μ.5 Sn:Pt = : Photon energy / ev k 2 χ(k) /Å k / Å - Sn K-edge.5 Sn:Pt = :.5 Sn:Pt = 9: Photon energy / ev k 2 χ(k) /Å Sn K-edge Sn:Pt = : Sn:Pt = 9: k / Å - Figure S9. Ex-situ XAFS spectra at Pt L III-edge, Co K-edge and Sn K-edge for SnO 2/Pt 3Co/C samples (Pt/Sn=9/ and /) and ADT 5, cycles. The ex-situ XANES spectra and EXAFS oscillations and Fourier transforms and ADT 5, cycles did not change, respectively, which suggests that the electronic states and local structures of Pt, Co and Sn atoms in the SnO 2/Pt 3Co/C samples remained unchanged after the ADT 5, load cycles. S3

14 Table S. EXAFS curve-fitting results for the SnO 2/Pt 3Co/C (Pt/Sn=/), Pt 3Co/C (TKK, TEC36E52), and Pt/C (TKK, TECE5E-HT) after the aging at RDE under under N 2-bubbling in k-range = 3-4 A - and R-range =.4- A. SnO 2 /Pt 3 Co/C (Pt/Sn=/) Potential / V vs RHE CN DW / A 2 ΔE / ev R-factor Pt-Co Pt-Pt Pt-O Pt-Co Pt-Pt Pt-O Pt-Co Pt-Pt Pt-O Pt-Co Pt-Pt Pt-O.4. ± ±.9-32 ± 26 6 ± 5.32 ± ± 2.72± ±.4 ± ± 9.54 ± ± ± ± ± ± 8 2 ± ± ± ± ±.2 ±. 47 ± ± 57-5 ± 9.6 ± ± ± ± ± 4 2 ± (4) O-fix.8 2. ± ± ± ± 3.83 ± ± 4 2.7± ± ± ± 3.54 ± ± ± ± ± ± 8.85 ± ± ± Pt 3 Co/C (TKK, TEC36E52) Potential / V vs RHE CN DW / A 2 ΔE / ev Pt-Co Pt-Pt Pt-O Pt-Co Pt-Pt Pt-O Pt-Co Pt-Pt Pt-O Pt-Co Pt-Pt Pt-O ±.7 8. ± ± 9.89 ± ± ± ± ± ± ± ± 2.8 ± 9.8 ± ± ± ± ± ± 7 54 ± 9.5 ±.9.5 ± ± ± ± 7. ±. ± ± ± ± ± ± ± ±.3.4 ±. 49 ± ± 74 3 ± 4.86 ± ± ± ± ± 7 ±.6 2. ± ± ± ± ± ± ± ± ± ± 22 ±.92 ± ± ± 2 39 HT-Pt/C (TKK, TECE5E-HT) under N 2 -bubbling Potential / V vs RHE CN DW / A 2 ΔE / ev Pt-Pt Pt-O Pt-Pt Pt-O Pt-Pt Pt-O Pt-Pt Pt-O R-factor 3 (6) O-fix R-factor.4.3 ±.5-48 ± ± ± ±.9-48 ± ± ± ±.6-5 ± 6.42 ± ± 6 22 ±.8. ±.6 53 ± 4 9 ±.47 ± ± ± 4 8 ± ±..4 ±. 53 ± 5 53 ± 3.85 ± 3.85 ± 2.78 ± 4 3 ± ±.4-42 ± 6 9 ± 3.7 ± ± ± 6 8 ± ±. - 5 ± ± ± 5 7 S4

15 a) b) 5a) 5b) a) 2b) 6a) 6b) a) 3b) 7a) 7b) a) b) SnO 2 /Pt 3 Co/C(Pt/Sn=/) a).4 V: χ(k)k 2 ; b).4 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 2a).6 V, χ(k)k 2 ; 2b).6 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 3a).8 V, χ(k)k 2 ; 3b).8 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 4a) V, χ(k)k 2 ; 4b) V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 5a).8 V, χ(k)k 2 ; 5b).8 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 6a).6 V, χ(k)k 2 ; 6b).6 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 7a).4 V, χ(k)k 2 ; 7b).4 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} k-range = 3-4 A -, R-range =.4 A Figure S2. SnO 2/Pt 3Co/C (Pt/Sn=/). EXAFS oscillations and their associated Fourier transforms, and their curve fitting results for S5

16 a) b) 5a) 5b) a) 2b) 6a) 6b) a) 3b) 7a) 7b) a) b) Pt 3 Co/C (TKK, TEC36E52) a).4 V: χ(k)k 2 ; b).4 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 2a).6 V, χ(k)k 2 ; 2b).6 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 3a).8 V, χ(k)k 2 ; 3b).8 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 4a) V, χ(k)k 2 ; 4b) V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 5a).8 V, χ(k)k 2 ; 5b).8 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 6a).6 V, χ(k)k 2 ; 6b).6 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 7a).4 V, χ(k)k 2 ; 7b).4 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} k-range = 3-4 A -, R-range =.4 A Figure S2. EXAFS oscillations and their associated Fourier transforms, and their curve fitting results for Pt 3Co/C (TKK, TEC36E52). S6

17 a) b) 5a) 5b) a) 2b) 6a) 6b) a) 3b) 7a) 7b) a) b) HT-Pt/C (TKK, TECE5E-HT) a).4 V: χ(k)k 2 ; b).4 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 2a).6 V, χ(k)k 2 ; 2b).6 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 3a).8 V, χ(k)k 2 ; 3b).8 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 4a) V, χ(k)k 2 ; 4b) V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 5a).8 V, χ(k)k 2 ; 5b).8 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 6a).6 V, χ(k)k 2 ; 6b).6 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} 7a).4 V, χ(k)k 2 ; 7b).4 V, FT[χ(k)k 2 ] & Im{FT[χ(k)k 2 ]} k-range = 3-4 A -, R-range =.4 A Figure S22. EXAFS oscillations and their associated Fourier transforms, and their curve fitting results for Pt/C (TKK, TECE5E-HT). S7