Hydrogen Evolution Reaction in Alkaline Media: Alpha- or Beta-Nickel Hydroxide on the Surface of Platinum?

Transcription

1 Supporting Information for Hydrogen Evolution Reaction in Alkaline Media: Alpha- or Beta-Nickel Hydroxide on the Surface of Platinum? Xiaowen Yu, a Jun Zhao, b Li-Rong Zheng, c Yue Tong, a Miao Zhang, a Guochuang Xu, a Chun Li, a Jing Ma, b* and Gaoquan Shi a* a Department of Chemistry, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing , P. R. China. b School of Chemistry and Chemical Engineering, Nanjing University, Nanjing , P. R. China. c Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Science, Beijing , P. R. China. *gshi@tsinghua.edu.cn; majing@nju.edu.cn S1

2 Experimental details Materials and chemicals. Nickel nitrate hexahydrate (Ni(NO 3 ) 2 6H 2 O, 98%, Alfa Aesar), oleylamine (C18-content 80-90%, Acros), potassium hydroxide (KOH, 85%, Alfa Aesar), dipotassium phosphate (K 2 HPO 4 ), potassium dihydrogen phosphate (KH 2 PO 4 ), perchloric acid (HClO 4, 70%, AR), ethanol (AR) were used as received without further purification. Ultrapure Milli-Q water (resistivity = 18 MΩ cm) was used to prepare the electrolytes. Synthesis of α-ni(oh) 2 nanospheres and β-ni(oh) 2 nanoplates. α-ni(oh) 2 hollow spheres were synthesized according to the literature. S1 Typically, 0.291g (1 mmol) of Ni(NO 3 ) 2 6H 2 O was added into 20 ml ethanol in a bottle under magnetic stirring for about 10 min. Successively, 12 ml oleylamine/ethanol (1:5, v/v) mixture was quickly added into the above solution, and then this system was stirred for 30 min to produce a homogenous solution. Then, the obtained solution was transferred into a sealed Teflon-lined autoclave, and maintained at 180 o C for 15 h. The resulting green precipitates were collected and washed with cyclohexane/ethanol (1:1, v/v) mixture to remove the surfactant and residuals; finally, they were freeze dried into powders. β-ni(oh) 2 nanoplates were also synthesized through the same procedures except for replacing 20 ml ethanol by 20 ml deionized water. These two types of Ni(OH) 2 nanostructures were formed via gas bubbles-assisted soft template processes; thus their morphologies were determined by the reaction solutions (ethanol or water with oleylamine). S1 Preparation of α- or β-ni(oh) 2 modified Pt electrode. 1 mg α- or β-ni(oh) 2 powders were dispersed in 1 ml water/isopropanol (3:1, v/v) mixed solvent containing 10 µl Nafion solution (5 wt%). Then, this mixture was sonicated to form a homogenous ink. Pt rotating disk electrode (RDE) was polished with aluminum powders and then cleaned by water and ethanol before use, and finally dried by nitrogen gas. Typically, 2.5 µl of above Ni(OH) 2 ink was drop casted onto the Pt RDE (0.196 cm 2 ); the mass loading of Ni(OH) 2 for each electrode was 13 µg cm 2. Freshly prepared Pt RDE without modification was used for comparison. It should be noted here that the typical mass loading of Ni(OH) 2 on the surface of Pt is much lower than the widely used values (e.g., 200 µg cm 2 ) for preparing catalyst modified glassy carbon electrodes. Electrochemical studies. Electrochemical tests were performed at room temperature in a standard three-electrode cell by using a CHI 760 D electrochemical workstation (CH Instrument Inc.). A Pt, α- or β-ni(oh) 2 /Pt electrode was used as the working electrode, a Pt mesh and a saturated calomel electrode (SCE) were used as the counter and reference electrodes. The linear sweep voltammetry (LSV) curves in various electrolytes were conducted at a scan rate of 10 mv s 1 and a rotating rate of 1,600 r.p.m. The ir-drop for LSV curves were all directly compensated by electrochemical workstation. The current-time dependent stability tests for various electrodes were performed at a constant potential of 0.09 V vs. RHE in 0.1 M KOH solution. All of the stability tests were not ir-compensated. The electrochemical impedance spectra (EIS) were recorded at open circuit potentials and the related frequencies ranged from 100 khz to 1 Hz with a 5 mv amplitude. The electrolytes (0.1 M KOH, 1.0 M KOH, 0.1 M PBS, 0.1 M HClO 4 ) used for electrochemical testing were S2

3 deaerated by nitrogen bubbling and kept in nitrogen circumstance during tests. The potentials recorded from electrochemical tests were all calibrated to the reversible hydrogen electrode (E RHE ) following the equation: E RHE = E SCE ph, where, the E SCE is the potential directly measured from the SCE reference electrode. The current densities for Pt electrode were all normalized by its geometric surface area of cm 2. Characterizations. Transmission electron micrographs (TEM) and selected area electron diffraction (SAED) patterns were recorded on a Tecnai F20 transmission electron microscope at 200 kv. The X-ray diffraction (XRD) patterns were conducted on a D8 Advanced X-ray diffractometer (XRD) with Cu Kα radiation (λ = nm, Bruker, Germany). The Fourier Transform Infrared spectra (FTIR) were taken out by using a Lambda 35 spectrometer (PerkinElmer FT-IR C101973, USA). Raman spectra were recorded on a LabRAM HR Raman spectrometer (Horiba Jobin Yvon) with a 532-nm laser beam. X-ray photoelectron spectra (XPS) were collected on an ESCALAB 250 photoelectron spectrometer (Thermo Fisher) with Al Kα as the X-ray source at 150 W and the pass energy of 30 ev for a high resolution scan. The Ni-K edge X-ray absorption near-edge structure (XANES) spectra were carried out at 1W1B beamline of Beijing Synchrotron Radiation Facility. In-Situ Raman analysis. A custom-built Teflon cell with a quartz window (Figure S0) was used for in-situ Raman monitoring the electrochemical processes. In this electrochemical cell, the working electrode is a modified Pt disk electrode (surface area = cm 2 ) that was assembled at the bottom of the cell and underneath the quartz window; the counter and reference electrodes are a Pt wire and a KCl saturated Ag/AgCl electrode. Current-voltage curves were collected using a CHI 760D electrochemical workstation. The electrolyte was 0.1 M KOH. In-situ Raman spectra of the electrodes were recorded using a confocal Raman microscopic spectrometer (LabRam HR, Horiba Jobin Yvon). Raman spectra were collected from the same surface of sample at 100% ND filler with 532-nm laser excitation. Figure S0. A digital picture of the electrochemical cell used for in-situ Raman tests. S3

4 Density-function theory (DFT) calculations. DFT calculations are performed by employing the generalized gradient approximation in the Perdew-Burke-Ernzerhof form (GGA-PBE) S2 and the projector augment wave method, as implemented in Vienna ab initio simulation package (VASP) S3, S4. The van der Waals correction (vdw-df2 functional) S5, S6 is introduced to describe the long-rang dispersion interaction. The cutoff energy for the plane waves is set to be 500 ev. The convergence threshold of the geometry optimizations is set to be ev in energy and 0.01 ev Å 1 in force. To avoid periodic interactions, a vacuum layer as large as 25 Å is used along the c direction normal to the substrate. The Monkhorst-Pack S7 sets of and k-points are used for the Brillouin Zone integration in geometries relaxations for the bulk materials and other slab models, respectively. For the calculations of the density of states (DOS), the k-point mesh is increased to For the two cleaved layers of Pt (111) surface, a 5 5 unit cell consisting of 50 Pt atoms is chosen as the supercell. In the related theoretical slab models, the upper 25 Pt atoms are fully relaxed without any symmetry or direction restrictions, while the remaining atoms are kept frozen during the computational process. The α-ni(oh) 2 (110) and β-ni(oh) 2 (100) nanostructures, consisting of 23 and 28 atoms, respectively, are absorbed onto the Pt (111) substrate to simulate the properties of the electrocatalysts. This simulated surface coverage of α- or β-ni(oh) 2 on the surface of Pt electrode is the same to that of the tested electrode. S4

5 Supplementary Tables Table S1. Summary of HER performances at Pt related electrodes. Sample Electrolyte Overpotential Current density Reference (mv, at 4 ma (ma cm 2, at cm 2 ) 0.07 V vs. RHE) 0.1 M KOH β-ni(oh) 2 /Pt 1.0 M KOH This work 0.1 M PBS Ni(OH) 2 /Pt-islands/Pt(111) 0.1 M KOH ~110 ~2.50 Science 2011, 334, 1256 Pt NWs/SL-Ni(OH) M KOH Nat. Commun. 2015, 6, 1.0 M KOH Pt(pc) electrode 0.1 M KOH ~2.40 ECS Trans. 2012, 50, 1.0 M KOH ~ Ni(OH) 2 modified Pt surface 0.1 M KOH ~95.0 ~3.00 Angew. Chem. Int. Ed. 2012, 51, Pt electrode 0.1 M KOH ~70.0 ~5.00 Energy. Environ. Sci. 2013, 6, 1509 S5

6 Pt 3 Ni frames/ni(oh) 2 /C 0.1 M KOH ~60.0 ~6.00 Science, 2014, 343, 1339 Ni@NC 1.0 M KOH ~180 0 Adv. Mater., 2017, 29, Ni 2 P 1.0 M KOH ~100 ~2 ACS Catal., 2017, 7, 103 Table S2. Extended X-ray absorption fine structure (EXAFS) fitting parameters at the Ni K-edge for different samples. Sample Shell N [a] R (Å) [b] σ 2 (Å 2 ) [c] E 0 (ev) [d] R factor (%) α-ni(oh) 2 powder Ni-O Ni-Ni α-ni(oh) 2 /Pt Ni-O Ni-Ni α-ni(oh) 2 /Pt [f] Ni-O Ni-Ni β-ni(oh) 2 powder Ni-O Ni-Ni 6.0 [e] β-ni(oh) 2 /Pt Ni-O Ni-Ni β-ni(oh) 2 /Pt Ni-O Ni-Ni [a] N: coordination number; [b] R: bond distance; [c] σ 2 : Debye-Waller factor; [d] E 0 : the inner potential correction. [e] Fixed to 6 for the first Ni-Ni shell, taking β-ni(oh) 2 as the reference sample. [f] The modified electrode after stability test is marked as α-ni(oh) 2 /Pt or β-ni(oh) 2 /Pt. S6

7 Supplementary Figures Figure S1. TEM (a, b) and HRTEM (c) images of α-ni(oh) 2 ; inset of panel b is the corresponding SAED pattern of α-ni(oh) 2 nanosheet. TEM (d, e) and HRTEM (f) images of β-ni(oh) 2 ; inset of panel e is the corresponding SAED pattern of β-ni(oh) 2 nanosheet. TEM image in Figure S1a shows that the α-ni(oh) 2 spheres with core-shell structure have diameters of 2 to 4 µm. Each sphere has a solid core surrounded by ultrathin nanosheets (Figure S1b). The SAED pattern of α-ni(oh) 2 (inset in panel b) indicates its polycrystalline structure. High-resolution TEM image of an α-ni(oh) 2 nanosheet (Figure S1c) exhibits the lattice fringes with a d-spacing of 2.66 Å, corresponding to the (110) planes of α-ni(oh) 2. The hexagonal β-ni(oh) 2 nanoplates have edge lengths of about nm (Figure S1d). The SAED pattern of β-ni(oh) 2 shows perfect rhombus diffraction spots (Figure S1e), reflecting the high crystallinity of β-ni(oh) 2. The HRTEM image exhibits distinct lattice fringes of (100) planes of β-ni(oh) 2 with a d-spacing of 2.70 Å (Figure S1f). S7

8 Figure S2. (a) XRD pattern of α-ni(oh) 2 powder (black line) and its corresponding standard PDF card of JCPDS (red line). (b) XRD pattern of β-ni(oh) 2 powder (black line) and its corresponding standard PDF card of JCPDS (red line). XRD pattern in Figure S2a shows distinct diffraction peaks at 2θ = 12º, 25.4º, 33.4º, and 59.4º, corresponding to the (001), (002), (110), and (300) lattice planes of α-ni(oh) 2 (JCPDS ). The diffraction angles of (001) and (002) lattice planes are slightly larger than those listed in the standard PDF card of α-ni(oh) 2. These positive shifts are attributed to the anions (e.g., NO 3 ) and water molecules intercalated into the interlayer of α-ni(oh) 2 lattices. This XRD pattern does not show any peaks related to β-ni(oh) 2, reflecting the high purity of α-ni(oh) 2 sample at the XRD detection level. The asymmetric diffraction peak at about 2θ = 33.4º indicates the formation of turbostratic α-ni(oh) 2 phase. This is mainly due to the disorder alignment of nickel oxide sheets caused by their intercalated anions. The interlamellar spacing is calculated to be 0.74 nm, in accordance with the reported values of nm. The relatively low XRD intensity of α-ni(oh) 2 is attributed to its high structural disorders. The XRD diffraction peaks in Figure S2b at 2θ = 19.3º, 33.1º, 38.5º, 52.1º, 59.1º and 62.7º, are assigned to the (001), (100), (101), (102), (110), and (111) lattice planes of β-ni(oh) 2, respectively; these results are in good agreement with the standard card of β-ni(oh) 2 (JCPDS ). The interlamellar spacing of β-ni(oh) 2 is calculated to be 0.46 nm, in accordance with the reported values of nm. There is no water or anions in the interlayer of β-ni(oh) 2 ; thus the stacking structure of β-ni(oh) 2 is intact. The diffraction peaks in XRD pattern of β-ni(oh) 2 are sharp and strong, indicating the perfect crystalline structure of β-ni(oh) 2, in good agreement with the SAED result shown in the inset of Figure S1e. The synthesized β-ni(oh) 2 sample has a high purity; its XRD pattern does not show any peaks of impurities (e.g., α-ni(oh) 2 ). S8

9 Figure S3. FTIR spectra of α-ni(oh) 2 (a) and β-ni(oh) 2 (b) powders. In the FTIR spectra of α-ni(oh) 2, the strong peak located at about 3660 cm 1 is related to the O-H stretching in α-ni(oh) 2 lattice. The broad band at about cm 1 is assigned to the O-H stretching of free water molecules. The peaks in the range of 2400 to 2800 cm 1 are associated with the 2ν 3 of NO 3. The peak at about 1630 cm 1 is the O-H bend of free water molecules. The sharp peak at 1490 cm 1 is associated with the O-H bend in α-ni(oh) 2 lattice. The peaks located at 1310, 1042, 992 cm 1 are related to the ν 3 or ν 1 of NO 3 cations. The band at about 650 cm 1 is assigned to the lattice mode of α-ni(oh) 2. S8 In the FTIR spectra of β-ni(oh) 2, the sharp and strong peak at 3630 cm 1 is assigned to the stretching of O-H groups, indicating the high crystallinity of β-ni(oh) 2. The broad band at around 1400 cm 1 is related to the E g and A 2u combination mode. The strong peaks lower than 600 cm 1 are related to the A 1g and acoustic mode combination of β-ni(oh) 2 lattice. S8 S9

10 Figure S4. (a) LSV curves for the α-ni(oh) 2 /Pt electrodes with different mass loadings. (b) LSV curves for the β-ni(oh) 2 /Pt electrodes with different mass loadings. LSV curves were all tested in 0.1 M KOH electrolyte at a scan rate of 10 mv s 1 and a rotating rate of 1,600 r.p.m.; the curves are ir-compensated. Figure S5. Cyclic voltammograms of Pt (a), α-ni(oh) 2 /Pt (b), and β-ni(oh) 2 /Pt (c) electrodes in N 2 -saturated 0.1 M KOH electrolyte at a scan rate of 20 mv s 1 without rotation. In Figure S5, in the potential range of V vs. RHE, the shadow areas are related to the adsorption of hydrogen atoms on the surface of Pt electrode. These adsorbed hydrogen atoms are formed at a potential that is positive of the Nernst potential for HER (0 V vs. RHE), thus are usually called underpotentially deposited hydrogen (denoted as H upd ). Integration of the I-V curve related to H upd acquires the total coulombic charge. Dividing this charge by 210 µc cm pt 2 can yield the electrochemical surface area of Pt (ECSA Pt ). S9 The decreased ECSA Pt for α-ni(oh) 2 /Pt or β-ni(oh) 2 /Pt electrode relative to pure Pt electrode is attributed to the coverage of Ni(OH) 2 clusters on the Pt surface, indicating that Ni(OH) 2 clusters selectively block the Pt sites for H upd. It should be noted that the H upd species are in the strongly adsorbed state on the surface of Pt, which are different from the weakly adsorbed hydrogen species (H ads ) formed at potentials negative of the Nernst potential for HER. S10 These H ads have balanced interaction with Pt in order to combine with Pt and successively desorb from Pt. S10

11 Figure S6. LSV curves of Pt, α-ni(oh) 2 /Pt, β-ni(oh) 2 /Pt, Au, α-ni(oh) 2 /Au, β-ni(oh) 2 /Au, GC, α-ni(oh) 2 /GC, and β-ni(oh) 2 /GC electrodes in 0.1 M KOH electrolyte at a scan rate of 10 mv s 1 and a rotating rate of 1600 r.p.m.; the curves are ir-compensated. Figure S7. (a) LSV curves for Pt, α-ni(oh) 2 /Pt, and β-ni(oh) 2 /Pt electrodes in 1.0 M KOH electrolyte at a scan rate of 10 mv s 1 and a rotating rate of 1600 r.p.m.; the curves were collected with ir-compensation. (b) The Tafel plots based on the LSV curves shown in panel a. Figure S8. (a) LSV curves for Pt, α-ni(oh) 2 /Pt, and β-ni(oh) 2 /Pt electrodes in 0.1 M PBS at a scan rate of 10 mv s 1 and a rotating rate of 1600 r.p.m.; the curves were collected with ir-compensation. (b) The Tafel plots based on the LSV curves shown in panel a. S11

12 Figure S9. (a-b) N 2 adsorption/desorption isotherms of α-ni(oh) 2 (a) and β-ni(oh) 2 samples (b). Figure S10. (a-c) LSV curves of α-ni(oh) 2 /Pt and β-ni(oh) 2 /Pt electrodes in N 2 -saturated 0.1 M KOH (a), 1.0 M KOH (b), and 0.1 M PBS (c) electrolytes at a scan rate of 10 mv s 1 and rotating rate of 1600 r.p.m., the current densities were normalized by the Brunauer-Emmett-Teller (BET) surface area of Ni(OH) 2 powders. (d) Summary of HER overpotentials (η) at 0.5 ma cm 2 BETNi for α- or β-ni(oh) 2 /Pt electrode in 0.1 M KOH, 1.0 M KOH, or 0.1 M PBS electrolyte based on LSV curves shown in panels a-c. (e) Summary of HER current densities at 0.10 V vs. RHE for α- or β-ni(oh) 2 /Pt electrode in 0.1 M KOH, 1.0 M KOH, or 0.1 M PBS electrolyte based on LSV curves shown in panels a-c. S12

13 Figure S11. Stability test of the β-ni(oh) 2 nanoplates modified Pt foil electrode; the insets are the SEM (left) and TEM (right) images of β-ni(oh) 2 nanoplates after long-time stability test. Figure S12. (a) Ni 2p XPS spectra of α- and β-ni(oh) 2 /Pt electrodes before and after stability test. (b) O 2p XPS spectra of α- and β-ni(oh) 2 /Pt electrodes before and after stability test. (c) Ni-K edge XANES spectra of α- and β-ni(oh) 2 /Pt electrodes before and after stability test. (d) Magnitude of k 3 -weighted Fourier transforms and fitting results of the Ni-K edge XANES spectra for α- and β-ni(oh) 2 /Pt electrodes before and after stability test. In above spectra, the electrodes tested after stability test were all marked as α- Ni(OH) 2 /Pt or β-ni(oh) 2 /Pt electrode. S13

14 Figure S13. Ni K-edge derivative XANES spectra in E-space for Ni foil, α- or β-ni(oh) 2 powders, and α- or β-ni(oh) 2 /Pt electrode. Figure S14. Ni K-edge EXAFS k 3 χ(k) oscillation functions of α- and β-ni(oh) 2 /Pt electrodes. S14

15 Figure S15. (a-c) LSV curves of α-ni(oh) 2 /Pt and β-ni(oh) 2 /Pt electrodes in N 2 -saturated 0.1 M KOH (a), 1.0 M KOH (b), and 0.1 M PBS (c) electrolytes at a scan rate of 10 mv s 1 and a rotating rate of 1600 r.p.m., the current densities were normalized by the active surface area of Pt. (d) Summary of the HER overpotentials (η) at 10 ma cm 2 Pt for α- or β-ni(oh) 2 /Pt electrode in 0.1 M KOH, 1.0 M KOH, or 0.1 M PBS electrolyte based on the LSV curves shown in panels a-c. (e) Summary of the HER current densities at 0.10 V vs. RHE for α- or β-ni(oh) 2 /Pt electrode in 0.1 M KOH, 1.0 M KOH, or 0.1 M PBS electrolyte based on the LSV curves shown in panels a-c. S15

16 Figure S16. Raman spectra of α-ni(oh) 2 (a) and β-ni(oh) 2 (b) on the surfaces of glass sheet and Pt foil. Figure S17. (a-b) Raman spectra of β-ni(oh) 2 /Pt electrode before and after several LSV tests at low (a) and high (b) wavenumbers in 0.1 M KOH electrolyte. The spectrum of β-ni(oh) 2 /Pt electrode after LSV tests was collected by removing the bubbles upon electrodes and collected at the same place. S16

17 Figure S18. (a) Optimized geometric structures of bulk Pt, bulk α-ni(oh) 2, bulk β-ni(oh) 2, α-ni(oh) 2 (110)/Pt(111) complex, β-ni(oh) 2 (100)/Pt(111) complex, H 2 O@α-Ni(OH) 2 /Pt complex, H 2 O@β-Ni(OH) 2 /Pt complex, and the mediate H@α-Ni(OH) 2 /Pt and H@β-Ni(OH) 2 /Pt; for clarity, the adsorbed H atom and H 2 O molecule in the top site on Pt surface are colored in green. (b) The charge difference isosurfaces of α-ni(oh) 2 /Pt and β-ni(oh) 2 /Pt complexes; cyan and light yellow isosurfaces represent regions of hole and electron accumulations, respectively; the isovalue is e/bohr S4. In Figure S18a, the selected crystal face of (110) for α-ni(oh) 2 or (100) for β-ni(oh) 2 was in consistent with the HRTEM results (Figure S1c and S1f), which indicate that the mainly exposed crystal face for α-ni(oh) 2 and β-ni(oh) 2 nanostructure is (110) and (100), respectively. The simulated surface coverage of α- or β-ni(oh) 2 on the surface of Pt electrode is also in accordance with the experimental results shown in Figure S5. The displayed geometric structures were all carefully optimized. In Figure S18b, the top views (upper) and side views (below) of charge difference isosurfaces of α-ni(oh) 2 /Pt and β-ni(oh) 2 /Pt electrodes are displayed. The cyan isosurfaces represent the regions of hole accumulation, and light yellow isosurfaces depict the regions of electron accumulation. In side views of charge difference isosurfaces, we can see that Pt atoms under Ni(OH) 2 clusters are accumulated with lots of holes, implying that Pt atoms transfer electrons to Ni(OH) 2. This phenomenon is in consistent with the XANES results S17

18 shown in Figure 2c, which indicate that the shift of pre-edges for Ni(OH) 2 samples on the Pt surface was attributed to the electron transfers between Pt and Ni(OH) 2. In addition, a large amount of charges accumulated around Pt atoms would greatly improve the activity of nearby Pt atoms to adsorb the hydrogen atoms (H ads ), and thus largely promote the Ni(OH) 2 /Pt electrode for the whole steps of HER. Supplementary References (S1) Gao, M.; Sheng, W.; Zhuang, Z.; Fang, Q.; Gu, S.; Jiang, J.; Yan, Y. Efficient Water Oxidation Using Nanostructured Alpha-Nickel-Hydroxide as an Electrocatalyst. J. Am. Chem. Soc. 2014, 136, (S2) Blochl, P. E. Projector Augmented-Wave Method. Phys. Rev. B 1994, 50, (S3) Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, (S4) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, (S5) Klimes, J.; Bowler, D. R.; Michaelides, A. Chemical Accuracy for the Van der Waals Density Functional. J. Phys-condens. Mat. 2010, 22, (S6) Klimes, J.; Bowler, D. R.; Michaelides, A. Van der Waals Density Functionals Applied to Solids. Phys. Rev. B 2011, 83, (S7) Monkhorst, H. J.; Pack, J. D. Special Points For Brillouin-Zone Integrations. Phys. Rev. B 1976, 13, (S8) Hall, D. S.; Lockwood, D. J.; Poirier, S.; Bock, C.; MacDougall, B. R. Raman and Infrared Spectroscopy of Alpha and Beta Phases of Thin Nickel Hydroxide Films Electrochemically Formed on Nickel. J Phys. Chem. A 2012, 116, (S9) Rheinländer, P.; Henning, S.; Herranz, J.; Gasteiger, H. A. Comparing Hydrogen Oxidation and Evolution Reaction Kinetics on Polycrystalline Platinum in 0.1 M and 1 M KOH. ECS Trans. 2012, 50, (S10) Subbaraman, R.; Tripkovic, D.; Strmcnik, D.; Chang, K.-C.; Uchimura, M.; Paulikas, A. P.; Stamenkovic, V.; Markovic, N. M. Enhancing Hydrogen Evolution Activity in Water Splitting by Tailoring Li + -Ni(OH) 2 -Pt Interfaces. Science 2011, 334, S18