High-Performance Electrocatalyst for Hydrogen Evolution Reaction ...
Supporting Information for
High-Performance Electrocatalysis for Hydrogen Evolution Reaction Using Se-Doped Pyrite-Phase Nickel Diphosphide Nanostructures Junqiao Zhuo,†,‡ Miguel Cabán-Acevedo,† Hanfeng Liang,†,# Leith Samad,† Qi Ding,† Yongping Fu,† Meixian Li,*,‡ and Song Jin*,† †
Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue,
Madison, Wisconsin 53706, United States; ‡Institute of Analytical Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China; #College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China.
*
E-mail: [email protected].
S1
1.
ADDITIONAL EXPERIMENTAL DETAILS AND ESTIMATION OF TURNOVER
FREQUENCY 1. Graphite Disk Substrate and Carbon Fiber Paper Preparation. Graphite disk substrates (6.0 mm diameter; ~1 mm thick) were prepared by cutting and mechanically thinning slices of a graphite rod (Ultra Carbon Corp., Ultra “F” Purity). Slices of the graphite rod were polished on both sides with sand paper. The graphite disks were cleaned by sequentially sonicating (100 W) in ethnol and deionized water for 10 min, respectively. Then the clean graphite disks were dried in a forced-air oven at 120 °C. Carbon fiber paper substrates were purchased from Fuel Cell Earth Corp. with a thickness of 0.19 mm. The cut carbon fiber paper was etched by plasma for 10 min at 150 W firstly, then heated to 700 oC for 10 min to make it hydrophilic. 2. Estimation of Active Site Density and Per-Site Turnover Frequency (TOF) To estimate the active surface site density and per-site turnover frequency (TOF) for the NiP1.93Se0.07 catalyst, we used cyclic voltammetry (CV) scans to determine the double-layer capacitance (Cdl), and further calculate the active surface area of NiP1.93Se0.07 on graphite disk (NiP1.93Se0.07/GD). A polished glassy carbon electrode was considered as a flat electrode and used as a control, and its Cdl is determined to be 0.11 mF cm-2. The roughness factor of NiP1.93Se0.07/GD (basically the surface area ratio between the catalyst vs. the glassy carbon electrode): 6.49 mF cm2 59 0.11 mF cm 2
The number of surface catalytic sites on the surface of flat catalyst can be calculated based on crystal structure of pyrite-phase NiP1.93Se0.07. Using the lattice parameter of cubic
S2
NiP1.93Se0.07 (a=5.49 Å) and assuming one active site per Ni-X2 dumbell (which translates into two active sites per square 100 face of one cubic unit cell), the density of surface active sites is:
2
5.4910
8
cm
2
6.6 1014 atom cm2
The density of surface active atoms of NiP1.93Se0.07/GD on geometric area: 4.4 1014 atom cm-2 59 3.9 1016 atom cm2
Turnover frequency (TOF) at an overpotential of 102 mV (a current density of 10 mA cm-2): 0.01 A 1 C 1 mol 6.02 1023 e 1 1 cm2 H 2 s 1 0 . 8 1 cm2 1 s 96485C 1 mol 2 e 3.9 1016 atom surface site
Note that because the nature of the active sites of the catalyst is not clearly understood yet and the real surface area for the nanostructured heterogeneous catalyst such as the ones reported here is hard to accurately determine, this result is really only an estimate.
2. SUPPORTING FIGURES
Figure S1. The illustration of the autoclave apparatus to prepare Ni(OH)2 nanoflakes on graphite or carbon paper substrates.
S3
Figure S2. The simplified Randles equivalent circuit used to fit the arcs in EIS spectra, which consists of a resistor (Rs) in series with a parallel arrangement of a resistor (Rct) and a constant phase element (CPE).
Figure S3. SEM images (a) and PXRD pattern (b) of the Ni(OH)2·0.75H2O nanoflake precursor in comparison with standard PXRD pattern (PDF#38-0715). The stars mark the diffraction peaks from graphite disk substrate.
S4
Figure S4. SEM images (a) and XRD patterns (b, c) of NiP2-xSex prepared at different conversion temperatures of 400 , 500 , and 600 oC with the same ratio of n(P):n(Se) = 3:2. The standard pattern in (b) and (c) is NiP2 (PDF#21-0590).
Figure S5. EDS elemental mapping of (a) NiP2, (b) NiP1.93Se0.07, (c) NiP0.09Se1.91, and (d) NiSe2.
S5
The scale bars in the images are 500 nm.
Table S1. Comparison of the catalytic performance of the NiP1.93Se0.07 nanostructures on carbon paper electrode reported herein with other recently reported high performance HER catalysts in 0.5 M H2SO4.
Catalysts
η @ 10 mA cm-2 (mV vs. RHE)
Tafel slope (mV dec-1)
Exchange current density (μA cm-2)
Ref.
NiP1.93Se0.07 nanoflakes
84
41
20
this work
CoPS nanoplates
48
56
984
S1
Porous NiSe2 nanosheets
135
37.2
6.46
S2
CoS2 nanowires
145
51.6
15.1
S3
CoSe2 nanoparticles
137
42.1
4.9 ± 1.4
S4
NiSe2 nanoparticles
147
50.1
/
S4
NiP2 nanosheet
75
51
260
S5
MoP nanoparticles
90
45
120
S6
Ni2P
130 (20 mA cm-2)
46
33
S7
MoP|S
64
50
570
S8
MoP nanoparticles
125
54
86
S9
FeP nanowire
55
38
420
S10
Cu3P nanowire
143
67
180
S11
WP nanoparticles
120
54
45
S12
C3N4@N-Graphene films
80
49.1
430
S13
S6
References Cited in the Supporting Information S1. Cabán-Acevedo, M.; Stone, M. L.; Schmidt, J. R.; Thomas, J. G.; Ding, Q.; Chang, H. C.; Tsai, M. L.; He, J. H.; Jin, S. Nat. Mater. 2015, DOI: http://dx.doi.org/10.1038/nmat4410. S2. Liang, H.; Li, L.; Meng, F.; Dang, L.; Forticaux, A.; Wang, Z.; Jin, S. Chem. Mater. 2015, 27, 5702-5711. S3. Faber, M. S.; Dziedzic, R.; Lukowski, M. A.; Kaiser, N. S.; Ding, Q.; Jin, S. J. Am. Chem. Soc. 2014, 136, 10053-10061. S4. Kong, D.; Wang, H.; Lu, Z.; Cui, Y. J. Am. Chem. Soc. 2014, 136, 4897-4900. S5. Jiang, P.; Liu, Q.; Sun, X. Nanoscale 2014, 6, 13440-13445. S6. McEnaney, J. M.; Crompton, J. C.; Callejas, J. F.; Popczun, E. J.; Biacchi, A. J.; Lewis, N. S.; Schaak, R. E. Chem. Mater. 2014, 26, 4826-4831. S7. Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. J. Am. Chem. Soc. 2013, 135, 9267-9270. S8. Kibsgaard, J.; Jaramillo, T. F. Angew. Chem., Int. Ed. 2014, 53, 14433-14437. S9. Xing, Z.; Liu, Q.; Asiri, A. M.; Sun, X. Adv. Mater. 2014, 26, 5702-5707. S10. Jiang, P.; Liu, Q.; Liang, Y.; Tian, J.; Asiri, A. M.; Sun, X. Angew. Chem., Int. Ed. 2014, 53, 12855-12859. S11. Tian, J.; Liu, Q.; Cheng, N.; Asiri, A. M.; Sun, X. Angew. Chem., Int. Ed. 2014, 53, 9577-9581. S12. McEnaney, J. M.; Crompton, J. C.; Callejas, J. F.; Popczun, E. J.; Read, C. G.; Lewis, N. S.; Schaak, R. E. Chem. Commun. 2014, 50, 11026-11028. S13. Duan, J.; Chen, S.; Jaroniec, M.; Qiao, S. Z. ACS Nano 2015, 9, 931-940.
S7
High-Performance Electrocatalysis for Hydrogen Evolution Reaction Using Se-Doped Pyrite-Phase Nickel Diphosphide Nanostructures Junqiao Zhuo,†,‡ Miguel Cabán-Acevedo,† Hanfeng Liang,†,# Leith Samad,† Qi Ding,† Yongping Fu,† Meixian Li,*,‡ and Song Jin*,† †
Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue,
Madison, Wisconsin 53706, United States; ‡Institute of Analytical Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China; #College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China.
*
E-mail: [email protected].
S1
1.
ADDITIONAL EXPERIMENTAL DETAILS AND ESTIMATION OF TURNOVER
FREQUENCY 1. Graphite Disk Substrate and Carbon Fiber Paper Preparation. Graphite disk substrates (6.0 mm diameter; ~1 mm thick) were prepared by cutting and mechanically thinning slices of a graphite rod (Ultra Carbon Corp., Ultra “F” Purity). Slices of the graphite rod were polished on both sides with sand paper. The graphite disks were cleaned by sequentially sonicating (100 W) in ethnol and deionized water for 10 min, respectively. Then the clean graphite disks were dried in a forced-air oven at 120 °C. Carbon fiber paper substrates were purchased from Fuel Cell Earth Corp. with a thickness of 0.19 mm. The cut carbon fiber paper was etched by plasma for 10 min at 150 W firstly, then heated to 700 oC for 10 min to make it hydrophilic. 2. Estimation of Active Site Density and Per-Site Turnover Frequency (TOF) To estimate the active surface site density and per-site turnover frequency (TOF) for the NiP1.93Se0.07 catalyst, we used cyclic voltammetry (CV) scans to determine the double-layer capacitance (Cdl), and further calculate the active surface area of NiP1.93Se0.07 on graphite disk (NiP1.93Se0.07/GD). A polished glassy carbon electrode was considered as a flat electrode and used as a control, and its Cdl is determined to be 0.11 mF cm-2. The roughness factor of NiP1.93Se0.07/GD (basically the surface area ratio between the catalyst vs. the glassy carbon electrode): 6.49 mF cm2 59 0.11 mF cm 2
The number of surface catalytic sites on the surface of flat catalyst can be calculated based on crystal structure of pyrite-phase NiP1.93Se0.07. Using the lattice parameter of cubic
S2
NiP1.93Se0.07 (a=5.49 Å) and assuming one active site per Ni-X2 dumbell (which translates into two active sites per square 100 face of one cubic unit cell), the density of surface active sites is:
2
5.4910
8
cm
2
6.6 1014 atom cm2
The density of surface active atoms of NiP1.93Se0.07/GD on geometric area: 4.4 1014 atom cm-2 59 3.9 1016 atom cm2
Turnover frequency (TOF) at an overpotential of 102 mV (a current density of 10 mA cm-2): 0.01 A 1 C 1 mol 6.02 1023 e 1 1 cm2 H 2 s 1 0 . 8 1 cm2 1 s 96485C 1 mol 2 e 3.9 1016 atom surface site
Note that because the nature of the active sites of the catalyst is not clearly understood yet and the real surface area for the nanostructured heterogeneous catalyst such as the ones reported here is hard to accurately determine, this result is really only an estimate.
2. SUPPORTING FIGURES
Figure S1. The illustration of the autoclave apparatus to prepare Ni(OH)2 nanoflakes on graphite or carbon paper substrates.
S3
Figure S2. The simplified Randles equivalent circuit used to fit the arcs in EIS spectra, which consists of a resistor (Rs) in series with a parallel arrangement of a resistor (Rct) and a constant phase element (CPE).
Figure S3. SEM images (a) and PXRD pattern (b) of the Ni(OH)2·0.75H2O nanoflake precursor in comparison with standard PXRD pattern (PDF#38-0715). The stars mark the diffraction peaks from graphite disk substrate.
S4
Figure S4. SEM images (a) and XRD patterns (b, c) of NiP2-xSex prepared at different conversion temperatures of 400 , 500 , and 600 oC with the same ratio of n(P):n(Se) = 3:2. The standard pattern in (b) and (c) is NiP2 (PDF#21-0590).
Figure S5. EDS elemental mapping of (a) NiP2, (b) NiP1.93Se0.07, (c) NiP0.09Se1.91, and (d) NiSe2.
S5
The scale bars in the images are 500 nm.
Table S1. Comparison of the catalytic performance of the NiP1.93Se0.07 nanostructures on carbon paper electrode reported herein with other recently reported high performance HER catalysts in 0.5 M H2SO4.
Catalysts
η @ 10 mA cm-2 (mV vs. RHE)
Tafel slope (mV dec-1)
Exchange current density (μA cm-2)
Ref.
NiP1.93Se0.07 nanoflakes
84
41
20
this work
CoPS nanoplates
48
56
984
S1
Porous NiSe2 nanosheets
135
37.2
6.46
S2
CoS2 nanowires
145
51.6
15.1
S3
CoSe2 nanoparticles
137
42.1
4.9 ± 1.4
S4
NiSe2 nanoparticles
147
50.1
/
S4
NiP2 nanosheet
75
51
260
S5
MoP nanoparticles
90
45
120
S6
Ni2P
130 (20 mA cm-2)
46
33
S7
MoP|S
64
50
570
S8
MoP nanoparticles
125
54
86
S9
FeP nanowire
55
38
420
S10
Cu3P nanowire
143
67
180
S11
WP nanoparticles
120
54
45
S12
C3N4@N-Graphene films
80
49.1
430
S13
S6
References Cited in the Supporting Information S1. Cabán-Acevedo, M.; Stone, M. L.; Schmidt, J. R.; Thomas, J. G.; Ding, Q.; Chang, H. C.; Tsai, M. L.; He, J. H.; Jin, S. Nat. Mater. 2015, DOI: http://dx.doi.org/10.1038/nmat4410. S2. Liang, H.; Li, L.; Meng, F.; Dang, L.; Forticaux, A.; Wang, Z.; Jin, S. Chem. Mater. 2015, 27, 5702-5711. S3. Faber, M. S.; Dziedzic, R.; Lukowski, M. A.; Kaiser, N. S.; Ding, Q.; Jin, S. J. Am. Chem. Soc. 2014, 136, 10053-10061. S4. Kong, D.; Wang, H.; Lu, Z.; Cui, Y. J. Am. Chem. Soc. 2014, 136, 4897-4900. S5. Jiang, P.; Liu, Q.; Sun, X. Nanoscale 2014, 6, 13440-13445. S6. McEnaney, J. M.; Crompton, J. C.; Callejas, J. F.; Popczun, E. J.; Biacchi, A. J.; Lewis, N. S.; Schaak, R. E. Chem. Mater. 2014, 26, 4826-4831. S7. Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. J. Am. Chem. Soc. 2013, 135, 9267-9270. S8. Kibsgaard, J.; Jaramillo, T. F. Angew. Chem., Int. Ed. 2014, 53, 14433-14437. S9. Xing, Z.; Liu, Q.; Asiri, A. M.; Sun, X. Adv. Mater. 2014, 26, 5702-5707. S10. Jiang, P.; Liu, Q.; Liang, Y.; Tian, J.; Asiri, A. M.; Sun, X. Angew. Chem., Int. Ed. 2014, 53, 12855-12859. S11. Tian, J.; Liu, Q.; Cheng, N.; Asiri, A. M.; Sun, X. Angew. Chem., Int. Ed. 2014, 53, 9577-9581. S12. McEnaney, J. M.; Crompton, J. C.; Callejas, J. F.; Popczun, E. J.; Read, C. G.; Lewis, N. S.; Schaak, R. E. Chem. Commun. 2014, 50, 11026-11028. S13. Duan, J.; Chen, S.; Jaroniec, M.; Qiao, S. Z. ACS Nano 2015, 9, 931-940.
S7
