Supporting Information for

Transcription

1 Supporting Information for Surface Amorphization: A Simple and Effective Strategy toward Boosting the Electrocatalytic Activity for Alkaline Water Oxidation Rong Zhang, Zao Wang, Ruixiang Ge, Xiang Ren, Shuai Hao, Fengli Qu, Gu Du, Abdullah M. Asiri, ʃ Baozhan Zheng,, * and Xuping Sun, * College of Chemistry, Sichuan University, Chengdu , China, College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu , China, Chengdu Institute of Geology and Mineral Resources, Chengdu , China, and ʃ Chemistry Department, King Abdulaziz University, Jeddah 21589, Saudi Arabia. R.Z. and Z.W. contributed equally to this work. * zheng_baozhan@outlook.com (B.Z.); sunxp@scu.edu.cn (X.S.) S-1

2 Content Experimental Section SEM image for NiO/CC....Figure S1 LSV curve......figure S2 SEM image after stability test...figure S3 XPS spectrum.figure S4 CVs for NiO/CC and after electrolysis... Figure S5 CVs for NiO/CC and after electrolysis... Figure S6 Comparison of OER performance.... Table S1 S-2

3 Experimental Section Materials: CC was bought from Hongshan District, Wuhan Instrument Surgical Instruments business, and treated in nitric acid (HNO 3 ) to serve as substrate for active materials. Ni(NO 3 ) 2 6H 2 O was purchased from Aladdin Ltd. in Shanghai. Hexamethylenetetramine (HMT) was provided by Beijing Chemical Works. HNO 3 and ethanol were purchased from Tianjin Chemical Corporation. K 2 B 4 O 7 4H 2 O was purchased by Chengdu Kelon Chemical Reagent Factory. RuCl 3 3H 2 O and Nafion (5 wt%) were bought from Sigma-Aldrich Chemical Reagent Co., Ltd. All chemical regents were used as received without further purification. Deionized water was made by the Millipore system and used in all experimental process. Preparation of NiO/CC and NiO@Ni-Bi/CC: Typically, CC was first treated with concentrated HNO 3, ethanol and deionized water by sonication to achieve a clean surface before use. Then CC was put into deionized water (36 ml) containing Ni(NO 3 ) 2 6H 2 O (1.45 g) and HMT (1.4 g). After vigorous stirring for several minutes, the aqueous solution and CC were transferred to a 50 ml Teflon-lined stainless-steel autoclave. It was heated at 100 C for 10 h to achieve Ni(OH) 2 /CC. The resulting Ni(OH) 2 /CC was washed with deionized water for several times and further annealed at 350 C in air to convert into NiO/CC. To realize the transformation of NiO/CC to NiO@Ni-Bi/CC, NiO/CC was used as the working electrode in a three-electrode setup with the potential of 1.0 V vs. Hg/HgO in 0.1 M K-Bi. After 45 min operating, the current density reaches a top value, indicating the successful synthesis of NiO@Ni-Bi/CC. Characterizations: XRD measurements were performed using a RigakuD/MAX 2550 diffractometer with Cu Kα radiation (λ= Å). SEM images were collected on a XL30 ESEM FEG scanning electron microscope at an accelerating voltage of 20 kv. TEM measurements were made on a HITACHI H-8100 electron microscopy (Hitachi, Tokyo, Japan) with an accelerating voltage of 200 kv. XPS measurements were performed on an ESCALABMK II X-ray photoelectron spectrometer using Mg as the exciting source. S-3

4 Electrochemical measurements: Electrochemical measurements were performed with a CHI 660E electrochemical analyzer (CH Instruments, Inc., Shanghai). In a typical three-electrode system, the NiO@Ni-Bi/CC was used as the working electrode, a platinum wire as the counter electrode and Hg/HgO as the reference electrode. The ohmic potential drop losses from the solution resistance has been substract unless specifically stated and all potentials were referenced to the reversible hydrogen electrode (RHE) scale. The potentials reported in this work were converted to the RHE with the following equation: E (RHE) = E (Hg/HgO) + ( ph) V. Linear sweep voltammetry (LSV) test was performed at a scan rate of 5 mv s -1 between 0.2 and 1.7 V (vs. Hg/HgO) at room temperature. TOF calculations: The slope is derived from the linear relationship. The number of active Ni species (m) is calculated using the formula: slope = n 2 F 2 m/4rt, where n representing the number of electrons transfer is 1 assuming an one-electron oxidation process of metal centers both in post-oer NiO/CC and post-oer NiO@Ni-Bi/CC, 1,2 F is Faradic constant (96485 C mol -1 ), m is the number of active species, and R and T are the ideal gas constant and the absolute temperature, respectively. TOF then can be calculated using the following equation: TOF = JA/4Fm (J: the current density; A: the geometrical electrode area; 4: the moles of electron consumption for one mole O 2 evolution). S-4

5 Figure S1. The cross-section SEM image for NiO/CC. S-5

6 Figure S2. LSV curve for in 0.1 M KOH. S-6

7 Figure S3. SEM image after stability test in 1.0 M KOH. S-7

8 Figure S4. XPS spectrum of after OER electrolysis in the B 1s region. S-8

9 Figure S5. CVs for (a) NiO/CC and (b) after OER electrolysis in the non-faradaic capacitance current range at scan rates of 10, 30, 50, 70, 90, and 110 mv s -1. S-9

10 Figure S6. CVs of (a) NiO/CC and (b) after OER electrolysis at different scan rates increasing from 10 to 60 mv s -1 in 1.0 M KOH. (c) Oxidation peak current vs. scan rate plots for NiO/CC and NiO@Ni-Bi/CC after OER electrolysis. S-10

11 Table S1. Comparison of OER performance for with other reported Ni-based electrocatalysts in alkaline media. Catalyst j (ma cm -2 ) η (mv) Electrolyte Ref M KOH NiO@Ni-Bi/CC M KOH This work M KOH Ni/NiO M KOH (3) NiO on Ni foam M NaOH (4) NiO x /Ni M KOH (5) NiO@NF M KOH (6) FeNC sheet/nio M KOH (7) N/C-NiO x M KOH (8) NiO/Fe trance M KOH (9) NiO NA/CC M KOH (9) Ni(OH) 2 NA/CC M KOH (10) α-ni(oh) 2 hollow spheres M KOH (11) 3D NF/PC/AN M KOH (12) β-ni(oh) M KOH (13) Ni(OH) 2 on O-MWCNTs M KOH (14) β-ni(oh) 2 nanosheets M KOH (15) Ni(OH) 2 /NF M KOH (16) Amorphous NiO 20 > M KOH (17) NiO x /C M KOH (18) S-11

12 References (1) Surendranath, Y.; Kanan, M. W.; Nocera, D. G. Mechanistic Studies of the Oxygen Evolution Reaction by a Cobalt-Phosphate Catalyst at Neutral ph. J. Am. Chem. Soc. 2010, 132, (2) Bediako, D. K.; Surendranath, Y.; Nocera, D. G. Mechanistic Studies of the Oxygen Evolution Reaction Mediated by a Nickel-Borate Thin Film Electrocatalyst. J. Am. Chem. Soc. 2013, 135, (3) Liang, J.; Wang, Y.; Wang, C.; Lu, S. In Situ Formation of NiO on Ni Foam Prepared with a Novel Leaven Dough Method as an Outstanding Electrocatalyst for Oxygen Evolution Reactions. J. Mater. Chem. A 2016, 4, (4) Browne, M. P.; Vasconcelos, J. M.; Coelho, J.; O'Brien, M.; Rovetta, A. A.; McCarthy, E. K.; Lyons, M. E. Improving the Performance of Porous Nickel Foam for Water Oxidation Using Hydrothermally Prepared Ni and Fe Metal Oxides. Sustain. Energy Fuels 2017, 1, (5) Han, G.; Liu,Y.; Hu, W.; Dong, B.; Li, X.; Shang, X.; Liu, C. Three Dimensional Nickel Oxides/Nickel Structure by in Situ Electro-Oxidation of Nickel Foam as Robust Electrocatalyst for Oxygen Evolution Reaction. Appl. Surf. Sci. 2015, 359, (6) Zheng, J.; Zhou, W.; Liu, T.; Liu, S.; Wang, C.; Guo, L. Homologous NiO//Ni 2 P Nanoarrays Grown on Nickel Foams: A Well Matched Electrode Pair with High Stability in Overall Water Splitting. Nanoscale 2017, 9, (7) Wang, J.; Li, K.; Zhong, H.; Xu, D.; Wang, Z.; Jiang, Z.; Wu, Z.; Zhang, X. Synergistic Effect between Metal-Nitrogen-Carbon Sheets and NiO Nanoparticles for Enhanced Electrochemical Water-Oxidation Performance. Angew. Chem. Int. Ed. 2015, 54, S-12

13 (8) Zhao, Y.; Nakamura, R.; Kamiya, K.; Nakanishi, S.; Hashimoto, K. Nitrogen-Doped Carbon Nanomaterials as Non-Metal Electrocatalysts for Water Oxidation. Nat. Commun. 2013, 4, (9) Nardi, K. L.; Yang, N.; Dickens, C. F.; Strickler, A. L.; Bent, S. F. Creating Highly Active Atomic Layer Deposited NiO Electrocatalysts for the Oxygen Evolution Reaction. Adv. Energy Mater. 2015, 5, (10) Cheng, N.; Liu, Q.; Tian, J.; Sun, X.; He, Y.; Zhai, S.; Asiri, A. M. Nickel Oxide Nanosheets Array Grown on Carbon Cloth as a High-Performance Three-Dimensional Oxygen Evolution Electrode. Int. J. Hydrogen Energy 2015, 40, (11) Gao, M.; Sheng, W.; Zhuang, Z.; Fang, Q.; Gu, S.; Jiang, J.; Yan, Y. Efficient Water Oxidation Using Nanostructured α-nickel-hydroxide as an Electrocatalyst. J. Am. Chem. Soc. 2014, 136, (12) Wang, J.; Zhong, H.; Qin, Y.; Zhang, X. ng, H.; Xu, D.; Wang, Z.; Jiang, Z.; Wu, Z.; Zhang, X. An Efficient Three-Dimensional Oxygen Evolution Electrode. Angew. Chem. Int. Ed. 2013, 52, (13) Jung, S. C.; Sim, S. L.; Soon, Y. W. Lim, C. M.; Hing, P.; Jennings, J. R. Synthesis of Nanostructured β-ni(oh) 2 by Electrochemical Dissolution-Precipitation and Its Application as a Water Oxidation Catalyst. Nanotechnol. 2016, 27, (14) Wang, L.; Chen, H.; Daniel, Q.; Duan, L.; Philippe, B.; Yang, Y.; Rensmo, H.; Sun, L. Promoting the Water Oxidation Catalysis by Synergistic Interactions between Ni(OH) 2 and Carbon Nanotubes. Adv. Energy Mater. 2016, 6, (15) Liang, H.; Li, L.; Meng, F.; Dang, L.; Zhuo, J.; Forticaux, A.; Jin, S. Porous Two-Dimensional Nanosheets Converted from Layered Double Hydroxides and Their Applications in Electrocatalytic Water Splitting. Chem. Mater. 2015, 27, S-13

14 (16) Luo, J.; Im, J.-H.; Mayer, M. T.; Schreier, M.; Nazeeruddin, M. K.; Park, N. G.; Tilley, S. D.; Fan, H.; Grätzel, M. Water Photolysis at 12.3% Efficiency via Perovskite Photovoltaics and Earth-Abundant Catalysts. Science 2014, 345, (17) Kuai, L.; Geng, J.; Chen, C.; Kan, E.; Liu, Y.; Wang, Q.; Geng, B. A Reliable Aerosol-Spray-Assisted Approach to Produce and Optimize Amorphous Metal Oxide Catalysts for Electrochemical Water Splitting. Angew. Chem. Int. Ed. 2014, 53, (18) Qiu, Y.; Xin, L.; Li, W. Electrocatalytic Oxygen Evolution over Supported Small Amorphous Ni-Fe Nanoparticles in Alkaline Electrolyte. Langmuir 2014, 30, S-14