Efficient and durable water electrolysis is a key technology for sustainable clean energy production.
In order to have an efficient electricity- gas conversion, materials that require low overpotential to
make water splitting possible must be used. Materials for the cathodic reaction that provides good
energetic efficiency have already been synthesized. However, the sluggish kinetics in the anode
reaction is still a limiting to make water splitting economical viable. Iridium and ruthenium oxides
are the benchmark materials for anodes in water splitting. Nevertheless, the high cost and scarcity
of this materials increase the industrial cost of the process. The fabrication of economical materials
with high activity is crucial to achieve the viability of water electrolysis. From earth abundant
elements, materials composed by nickel and iron are the ones that present the best prospect as
anodes for water splitting, and being possible to outperformed the benchmark Ir and Ru oxides
catalyst.
Deep eutectic solvents (DES) are a new family of ionic liquids. In the last decades, they have
become attractive because they are considering a green solvent. DES possess a wide potential
window, which make possible the electrodeposition of many metals without hydrogen evolution
in the cathode. Various metals with decorative and specific purposes have already electrodeposited
from them.
In the present work, First, a suitable potential for electrodeposition of Ni and Fe alloys in ethaline
DES solution was determined by cyclic voltammetry and confirmed with electrochemical
impedance spectroscopy. Then, the electrodeposition of the Ni, Fe and Ni-Fe alloys was carried
out at conditions that allows to obtain a well attached to the substrate and uniform films.
The metal composition of the alloys electrodeposited is found to be directly proportional to the
metal concentration in the ethaline solution.The as-deposited films then were characterized by
SEM. Ni and Fe samples present nodular and grain-crystal morphology respectively. Ni films
present a face cubic center crystallinity, iron film esasly oxidize into magnetite crystalline structure
and Ni-Fe alloys presents a crystalline phase of Ni Fe.
The films were tested as electrocatalyst for oxygen evolution reaction in alkaline media. It has
been found that the alloy with Ni:Fe 3:1 metal ratio presents the lowest overpotential of the
analyzed alloys, with a overpotential value of 316 mV at 10 mA∙cm-2 and a Tafel slope value of
62 mV∙dec-1 and durability on a 0.1 M NaOH electrolyte. XPS shows after OER a change valence
state from Ni metal to Ni+2
due to oxidation of the surface, while Fe is present in Fe+3 before and
after OER.

Efficient and durable water electrolysis is a key technology for sustainable clean energy production.
In order to have an efficient electricity- gas conversion, materials that require low overpotential to
make water splitting possible must be used. Materials for the cathodic reaction that provides good
energetic efficiency have already been synthesized. However, the sluggish kinetics in the anode
reaction is still a limiting to make water splitting economical viable. Iridium and ruthenium oxides
are the benchmark materials for anodes in water splitting. Nevertheless, the high cost and scarcity
of this materials increase the industrial cost of the process. The fabrication of economical materials
with high activity is crucial to achieve the viability of water electrolysis. From earth abundant
elements, materials composed by nickel and iron are the ones that present the best prospect as
anodes for water splitting, and being possible to outperformed the benchmark Ir and Ru oxides
catalyst.
Deep eutectic solvents (DES) are a new family of ionic liquids. In the last decades, they have
become attractive because they are considering a green solvent. DES possess a wide potential
window, which make possible the electrodeposition of many metals without hydrogen evolution
in the cathode. Various metals with decorative and specific purposes have already electrodeposited
from them.
In the present work, First, a suitable potential for electrodeposition of Ni and Fe alloys in ethaline
DES solution was determined by cyclic voltammetry and confirmed with electrochemical
impedance spectroscopy. Then, the electrodeposition of the Ni, Fe and Ni-Fe alloys was carried
out at conditions that allows to obtain a well attached to the substrate and uniform films.
The metal composition of the alloys electrodeposited is found to be directly proportional to the
metal concentration in the ethaline solution.The as-deposited films then were characterized by
SEM. Ni and Fe samples present nodular and grain-crystal morphology respectively. Ni films
present a face cubic center crystallinity, iron film esasly oxidize into magnetite crystalline structure
and Ni-Fe alloys presents a crystalline phase of Ni Fe.
The films were tested as electrocatalyst for oxygen evolution reaction in alkaline media. It has
been found that the alloy with Ni:Fe 3:1 metal ratio presents the lowest overpotential of the
analyzed alloys, with a overpotential value of 316 mV at 10 mA∙cm-2 and a Tafel slope value of
62 mV∙dec-1 and durability on a 0.1 M NaOH electrolyte. XPS shows after OER a change valence
state from Ni metal to Ni+2
due to oxidation of the surface, while Fe is present in Fe+3 before and
after OER.

[1] I.E. Agency, CO2 Emission from fuel combustion, IEA, United States, 2017, pp. 529.
[2] Y.W. Chen, S.-Y. Lin, C.-Y. Chiang, Molybdenum sulfide for hydrogen evolution reaction: The importance of solution dynamic wetting behavior in the drying process, Langmuir 33 (2017) 4638-4646.
[3] M.D. Merrill, R.C. Dougherty, Metal Oxide Catalysts for the Evolution of O2 from H2O, The Journal of Physical Chemistry C 112 (2008) 3655-3666.
[4] M. Görlin, J. Ferreira de Araújo, H. Schmies, D. Bernsmeier, S. Dresp, M. Gliech, Z. Jusys, P. Chernev, R. Kraehnert, H. Dau, P. Strasser, Tracking Catalyst Redox States and Reaction Dynamics in Ni–Fe Oxyhydroxide Oxygen Evolution Reaction Electrocatalysts: The Role of Catalyst Support and Electrolyte pH, Journal of the American Chemical Society 139 (2017) 2070-2082.
[5] B.J. Trześniewski, O. Diaz, D.A. Vermaas, A. Longo, W. Bras, M.T.M. Koper, W.A. Smith, In Situ observation of active oxygen species in Fe-containing Ni-based oxygen evolution catalysts: The Effect of pH on Electrochemical Activity, Journal of the American Chemical Society 137 (2015) 15112-15121.
[6] J. Qi, W. Zhang, R. Xiang, K. Liu, H.Y. Wang, M. Chen, Y. Han, R. Cao, Porous nickel–iron oxide as a highly efficient electrocatalyst for oxygen evolution reaction, Advanced Science 2 (2015) 1500199.
[7] M. Gong, Y. Li, H. Wang, Y. Liang, J.Z. Wu, J. Zhou, J. Wang, T. Regier, F. Wei, H. Dai, An advanced Ni–Fe layered double hydroxide electrocatalyst for water oxidation, Journal of the American Chemical Society 135 (2013) 8452-8455.
[8] F. Song, X. Hu, Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis, Nature Communications 5 (2014) 4477.
[9] M. Zhou, Q. Weng, X. Zhang, X. Wang, Y. Xue, X. Zeng, Y. Bando, D. Golberg, In situ electrochemical formation of core-shell nickel-iron disulfide and oxyhydroxide heterostructured catalysts for a stable oxygen evolution reaction and the associated mechanisms, Journal of Materials Chemistry A 5 (2017) 4335-4342.
[10] Z. Wang, J. Li, X. Tian, X. Wang, Y. Yu, K.A. Owusu, L. He, L. Mai, Porous nickel–iron selenide nanosheets as highly efficient electrocatalysts for oxygen evolution reaction, ACS Applied Materials & Interfaces 8 (2016) 19386-19392.
[11] P. Wang, Z. Pu, Y. Li, L. Wu, Z. Tu, M. Jiang, Z. Kou, I.S. Amiinu, S. Mu, Iron-doped nickel phosphide nanosheet arrays: An efficient bifunctional electrocatalyst for water splitting, ACS Applied Materials & Interfaces 9 (2017) 26001-26007.
[12] K. Fominykh, P. Chernev, I. Zaharieva, J. Sicklinger, G. Stefanic, M. Döblinger, A. Müller, A. Pokharel, S. Böcklein, C. Scheu, T. Bein, D. Fattakhova-Rohlfing, Iron-doped nickel oxide nanocrystals as highly efficient electrocatalysts for alkaline water splitting, ACS Nano 9 (2015) 5180-5188.
[13] A.P. Abbott, D. Boothby, G. Capper, D.L. Davies, R.K. Rasheed, Deep eutectic solvents formed between Choline Chloride and carboxylic acids:  Versatile Alternatives to Ionic Liquids, Journal of the American Chemical Society 126 (2004) 9142-9147.
[14] E.L. Smith, A.P. Abbott, K.S. Ryder, Deep Eutectic Solvents (DESs) and Their Applications, Chemical Reviews 114 (2014) 11060-11082.
[15] C.D. Gu, Y.H. You, Y.L. Yu, S.X. Qu, J.P. Tu, Microstructure, nanoindentation, and electrochemical properties of the nanocrystalline nickel film electrodeposited from choline chloride–ethylene glycol, Surface and Coatings Technology 205 (2011) 4928-4933.
[16] M. Steichen, M. Thomassey, S. Siebentritt, P.J. Dale, Controlled electrodeposition of Cu-Ga from a deep eutectic solvent for low cost fabrication of CuGaSe2 thin film solar cells, Physical Chemistry Chemical Physics 13 (2011) 4292-4302.
[17] P. Guillamat, M. Cortés, E. Vallés, E. Gómez, Electrodeposited CoPt films from a deep eutectic solvent, Surface and Coatings Technology 206 (2012) 4439-4448.
[18] M.Y. Gao, C. Yang, Q.B. Zhang, Y.W. Yu, Y.X. Hua, Y. Li, P. Dong, Electrochemical fabrication of porous Ni-Cu alloy nanosheets with high catalytic activity for hydrogen evolution, Electrochimica Acta 215 (2016) 609-616.
[19] M.Y. Gao, C. Yang, Q.B. Zhang, J.R. Zeng, X.T. Li, Y.X. Hua, C.Y. Xu, P. Dong, Facile electrochemical preparation of self-supported porous Ni-Mo alloy microsphere films as efficient bifunctional electrocatalysts for water splitting, Journal of Materials Chemistry 5 (2017) 5797-5805.
[20] U.E.I. Administration, International Energy Outlook 2017, in: U.E.I. Administration (Ed.), Independent statistics & Analysis, Washington D.C., 2017, pp. 76.
[21] H. Lund, Renewable energy strategies for sustainable development, Energy 32 (2007) 912-919.
[22] A. Landman, H. Dotan, G.E. Shter, M. Wullenkord, A. Houaijia, A. Maljusch, G.S. Grader, A. Rothschild, Photoelectrochemical water splitting in separate oxygen and hydrogen cells, Nature Materials 16 (2017) 646.
[23] M. Momirlan, T.N. Veziroglu, The properties of hydrogen as fuel tomorrow in sustainable energy system for a cleaner planet, International Journal of Hydrogen Energy 30 (2005) 795-802.
[24] S.Z. Baykara, Hydrogen as fuel: a critical technology?, International Journal of Hydrogen Energy 30 (2005) 545-553.
[25] J. Wang, Barriers of scaling-up fuel cells: Cost, durability and reliability, Energy 80 (2015) 509-521.
[26] R. Kothari, D. Buddhi, R.L. Sawhney, Comparison of environmental and economic aspects of various hydrogen production methods, Renewable and Sustainable Energy Reviews 12 (2008) 553-563.
[27] M.A. Manion, Ullmann's Encyclopedia of Industrial Chemistry, Choice: Current Reviews for Academic Libraries 50 (2012) 452-452.
[28] V.A. Kuuskraa, L.J. Pekot, Defining Optimum CO2 Sequestration Sites for Power and Industrial Plants A2 - Gale, J, in: Y. Kaya (Ed.) Greenhouse Gas Control Technologies - 6th International Conference, Pergamon, Oxford, 2003, pp. 609-614.
[29] J.A. Turner, A Realizable Renewable Energy Future, Science 285 (1999) 687.
[30] K. Zeng, D. Zhang, Recent progress in alkaline water electrolysis for hydrogen production and applications, Progress in Energy and Combustion Science 36 (2010) 307-326.
[31] J. Divisek, Low temperature fuel cells, Handbook of Fuel Cells, John Wiley & Sons, Ltd 2010.
[32] J. Koponen, A. Kosonen, V. Ruuskanen, K. Huoman, M. Niemelä, J. Ahola, Control and energy efficiency of PEM water electrolyzers in renewable energy systems, International Journal of Hydrogen Energy 42 (2017) 29648-29660.
[33] H. Wendt, G. Imarisio, Nine years of research and development on advanced water electrolysis. A review of the research programme of the Commission of the European Communities, Journal of Applied Electrochemistry 18 (1988) 1-14.
[34] T. Smolinka, FUELS – HYDROGEN PRODUCTION | Water Electrolysis A2 - Garche, Jürgen, Encyclopedia of Electrochemical Power Sources, Elsevier, Amsterdam, 2009, pp. 394-413.
[35] A.J. Bard, L.R. Faulkner, Electrochemical methods : fundamentals and applications, 2nd ed., Wiley, New York, 2001.
[36] B.V. Tilak, P.W.T. Lu, J.E. Colman, S. Srinivasan, Electrolytic Production of Hydrogen, in: J.O.M. Bockris, B.E. Conway, E. Yeager, R.E. White (Eds.) Comprehensive treatise of Electrochemistry: Electrochemical Processing, Springer US, Boston, MA, 1981, pp. 1-104.
[37] J. Milewski, G. Guandalini, S. Campanari, Modeling an alkaline electrolysis cell through reduced-order and loss-estimate approaches, Journal of Power Sources 269 (2014) 203-211.
[38] K.B. Oldham, J.C. Myland, 5 - Electrode Reactions, Fundamentals of Electrochemical Science, Academic Press, San Diego, 1994, pp. 149-186.
[39] R.L. Doyle, M.E.G. Lyons, The oxygen evolution reaction: Mechanistic concepts and catalyst design, in: S. Giménez, J. Bisquert (Eds.) Photoelectrochemical Solar Fuel Production: From Basic Principles to Advanced Devices, Springer International Publishing, Cham, 2016, pp. 41-104.
[40] N.T. Suen, S.F. Hung, Q. Quan, N. Zhang, Y.J. Xu, H.M. Chen, Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives, Chem Soc Rev 46 (2017) 337-365.
[41] I.C. Man, H.-Y. Su, F. Calle-Vallejo, H.A. Hansen, J.I. Martínez, N.G. Inoglu, J. Kitchin, T.F. Jaramillo, J.K. Nørskov, J. Rossmeisl, Cover Picture: Universality in oxygen evolution electrocatalysis on oxide surfaces (ChemCatChem 7/2011), ChemCatChem 3 (2011) 1085-1085.
[42] T.Y. Ma, S. Dai, S.Z. Qiao, Self-supported electrocatalysts for advanced energy conversion processes, Materials Today 19 (2016) 265-273.
[43] H. Ohno, Electrochemical aspects of ionic liquids, Wiley, Hoboken, N.J., 2005.
[44] H. Ohno, Physical Properties of Ionic Liquids for Electrochemical Applications, Electrodeposition from Ionic Liquids, Wiley-VCH Verlag GmbH & Co. KGaA2008, pp. 47-82.
[45] A.P. Abbott, G. Capper, K.J. McKenzie, K.S. Ryder, Electrodeposition of zinc–tin alloys from deep eutectic solvents based on choline chloride, Journal of Electroanalytical Chemistry 599 (2007) 288-294.
[46] T. Beyersdorff, T.J.S. Schubert, U. Welz-Biermann, W. Pitner, A.P. Abbott, K.J. McKenzie, K.S. Ryder, Synthesis of Ionic Liquids, Electrodeposition from Ionic Liquids, Wiley-VCH Verlag GmbH & Co. KGaA2008, pp. 15-46.
[47] K. Shahbaz, F.S. Mjalli, M.A. Hashim, I.M. Alashef, Prediction of deep eutectic solvents densities at different temperatures, Thermochimica Acta 515 (2011) 67-72.
[48] A. Yadav, S. Pandey, Densities and Viscosities of (Choline Chloride + Urea) Deep Eutectic Solvent and Its Aqueous Mixtures in the Temperature Range 293.15 K to 363.15 K, Journal of Chemical & Engineering Data 59 (2014) 2221-2229.
[49] Q. Zhang, K. De Oliveira Vigier, S. Royer, F. Jerome, Deep eutectic solvents: syntheses, properties and applications, Chemical Society Reviews 41 (2012) 7108-7146.
[50] A.P. Abbott, R.C. Harris, K.S. Ryder, C. D'Agostino, L.F. Gladden, M.D. Mantle, Glycerol eutectics as sustainable solvent systems, Green Chemistry 13 (2011) 82-90.
[51] T. Schubert, S. Zein El Abedin, A.P. Abbott, K.J. McKenzie, K.S. Ryder, F. Endres, Electrodeposition of Metals, Electrodeposition from ionic liquids, Wiley-VCH Verlag GmbH & Co. KGaA2008, pp. 83-123.
[52] A.P. Abbott, G. Capper, D.L. Davies, R.K. Rasheed, Ionic liquid analogues formed from hydrated metal salts, Chemistry – A European Journal 10 (2004) 3769-3774.
[53] S. Ghosh, S. Roy, Electrochemical copper deposition from an ethaline-CuCl2·2H2O DES, Surface and Coatings Technology 238 (2014) 165-173.
[54] D. Lloyd, T. Vainikka, L. Murtomäki, K. Kontturi, E. Ahlberg, The kinetics of the Cu redox couple in deep eutectic solvents, Electrochimica Acta 56 (2011) 4942-4948.
[55] E.L. Smith, J.C. Barron, A.P. Abbott, K.S. Ryder, Time Resolved in situ liquid atomic force microscopy and simultaneous acoustic impedance Electrochemical Quartz Crystal Microbalance Measurements: A Study of Zn Deposition, Analytical Chemistry 81 (2009) 8466-8471.
[56] H. Yang, X. Guo, N. Birbilis, G. Wu, W. Ding, Tailoring nickel coatings via electrodeposition from a eutectic-based ionic liquid doped with nicotinic acid, Applied Surface Science 257 (2011) 9094-9102.
[57] C. Gu, J. Tu, One-step fabrication of nanostructured Ni film with lotus effect from deep eutectic solvent, Langmuir 27 (2011) 10132-10140.
[58] A.P. Abbott, K. El Ttaib, K.S. Ryder, E.L. Smith, Electrodeposition of nickel using eutectic based ionic liquids, Transactions of the IMF 86 (2008) 234-240.
[59] R. Böck, S.E. Wulf, Electrodeposition of iron films from an ionic liquid (ChCl/urea/FeCl3 deep eutectic mixtures), Transactions of the IMF 87 (2009) 28-32.
[60] A.P. Abbott, K.E. Ttaib, G. Frisch, K.S. Ryder, D. Weston, The electrodeposition of silver composites using deep eutectic solvents, Physical Chemistry Chemical Physics 14 (2012) 2443-2449.
[61] H. Wang, Y. Jia, X. Wang, Y. Yao, D. Yue, Y. Jing, Electrochemical deposition of magnesium from analogous ionic liquid based on dimethylformamide, Electrochimica Acta 108 (2013) 384-389.
[62] P.K. Wang, Y.T. Hsieh, I.W. Sun, On the electrodeposition of arsenic in a choline chloride-ethylene glycol deep eutectic solvent, J. Electrochem. Soc. 164 (2017) D204-D209.
[63] Y.H. You, C.D. Gu, X.L. Wang, J.P. Tu, Electrodeposition of Ni–Co alloys from a deep eutectic solvent, Surface and Coatings Technology 206 (2012) 3632-3638.
[64] G. Saravanan, S. Mohan, Electrodeposition of Fe-Ni-Cr alloy from deep eutectic system containing choline chloride and ethylene glycol, Int J Electrochem Sc 6 (2011) 1468-1478.
[65] E. Gómez, P. Cojocaru, L. Magagnin, E. Valles, Electrodeposition of Co, Sm and SmCo from a deep eutectic solvent, Journal of Electroanalytical Chemistry 658 (2011) 18-24.
[66] T. Yanai, K. Shiraishi, Y. Watanabe, M. Nakano, T. Ohgai, K. Suzuki, H. Fukunaga, Electroplated Fe–Ni Films Prepared From Deep Eutectic Solvents, IEEE Transactions on Magnetics 50 (2014) 1-4.
[67] J.C. Malaquias, M. Steichen, M. Thomassey, P.J. Dale, Electrodeposition of Cu–In alloys from a choline chloride based deep eutectic solvent for photovoltaic applications, Electrochimica Acta 103 (2013) 15-22.
[68] J. Vijayakumar, S. Mohan, S. Anand Kumar, S.R. Suseendiran, S. Pavithra, Electrodeposition of Ni–Co–Sn alloy from choline chloride-based deep eutectic solvent and characterization as cathode for hydrogen evolution in alkaline solution, International Journal of Hydrogen Energy 38 (2013) 10208-10214.
[69] C. Yang, M.Y. Gao, Q.B. Zhang, J.R. Zeng, X.T. Li, A.P. Abbott, In-situ activation of self-supported 3D hierarchically porous Ni3S2 films grown on nanoporous copper as excellent pH-universal electrocatalysts for hydrogen evolution reaction, Nano Energy 36 (2017) 85-94.
[70] Q.B. Zhang, A.P. Abbott, C. Yang, Electrochemical fabrication of nanoporous copper films in choline chloride-urea deep eutectic solvent, Physical Chemistry Chemical Physics 17 (2015) 14702-14709.
[71] C. Du, B. Zhao, X.-B. Chen, N. Birbilis, H. Yang, Effect of water presence on choline chloride-2urea ionic liquid and coating platings from the hydrated ionic liquid, Scientific Reports 6 (2016) 29225.
[72] A. Lasia, Definition of impedance and impedance of electrical circuits, in: A. Lasia (Ed.) Electrochemical Impedance Spectroscopy and its Applications, Springer New York, New York, NY, 2014, pp. 7-66.
[73] J.I. Goldstein, D.E. Newbury, P. Echlin, D.C. Joy, C.E. Lyman, E. Lifshin, L. Sawyer, J.R. Michael, The SEM and Its Modes of Operation, in: J.I. Goldstein, D.E. Newbury, P. Echlin, D.C. Joy, C.E. Lyman, E. Lifshin, L. Sawyer, J.R. Michael (Eds.) Scanning Electron Microscopy and X-ray Microanalysis: Third Edition, Springer US, Boston, MA, 2003, pp. 21-60.
[74] A.A. Kityk, D.A. Shaiderov, E.A. Vasil'eva, V.S. Protsenko, F.I. Danilov, Choline chloride based ionic liquids containing nickel chloride: Physicochemical properties and kinetics of Ni(II) electroreduction, Electrochimica Acta 245 (2017) 133-145.
[75] T. Yanai, K. Shiraishi, Y. Watanabe, M. Nakano, T. Ohgai, K. Suzuki, H. Fukunaga, Electroplated Ni-Fe Films prepared from deep eutectic solvents, IEEE Transactions on Magnetics 50 (2014) 1-4.
[76] V.C. Kieling, Parameters influencing the electrodeposition of Ni-Fe alloys, Surface and Coatings Technology 96 (1997) 135-139.
[77] S. Fazli, M.E. Bahrololoom, Effect of plating time on electrodeposition of thick nanocrystalline permalloy foils, Transactions of the IMF 94 (2016) 92-98.
[78] E. Potvin, L. Brossard, Electrocatalytic activity of Ni-Fe anodes for alkaline water electrolysis, Materials Chemistry and Physics 31 (1992) 311-318.
[79] C.W. Su, E.L. Wang, Y.-B. Zhang, F.-J. He, Ni1−xFex (0.1<x<0.75) alloy foils prepared from a fluorborate bath using electrochemical deposition, Journal of Alloys and Compounds 474 (2009) 190-194.
[80] G. Cacciamani, A. Dinsdale, M. Palumbo, A. Pasturel, The Fe–Ni system: Thermodynamic modelling assisted by atomistic calculations, Intermetallics 18 (2010) 1148-1162.
[81] M.W. Louie, A.T. Bell, An Investigation of thin-film Ni–Fe oxide catalysts for the electrochemical evolution of oxygen, Journal of the American Chemical Society 135 (2013) 12329-12337.
[82] C.C.L. McCrory, S. Jung, J.C. Peters, T.F. Jaramillo, Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction, Journal of the American Chemical Society 135 (2013) 16977-16987.
[83] L. Trotochaud, S.L. Young, J.K. Ranney, S.W. Boettcher, Nickel–iron oxyhydroxide oxygen-evolution electrocatalysts: The role of intentional and incidental iron incorporation, Journal of the American Chemical Society 136 (2014) 6744-6753.
[84] J.R. Swierk, S. Klaus, L. Trotochaud, A.T. Bell, T.D. Tilley, Electrochemical study of the energetics of the oxygen evolution reaction at nickel iron oxyhydroxide catalysts, The Journal of Physical Chemistry C 119 (2015) 19022-19029.
[85] M. Gong, H. Dai, A mini review of NiFe-based materials as highly active oxygen evolution reaction electrocatalysts, Nano Research 8 (2015) 23-39.
[86] D. Friebel, M.W. Louie, M. Bajdich, K.E. Sanwald, Y. Cai, A.M. Wise, M.-J. Cheng, D. Sokaras, T.-C. Weng, R. Alonso-Mori, R.C. Davis, J.R. Bargar, J.K. Nørskov, A. Nilsson, A.T. Bell, Identification of highly active Fe sites in (Ni,Fe)OOH for electrocatalytic water splitting, Journal of the American Chemical Society 137 (2015) 1305-1313.
[87] R.L. Doyle, I.J. Godwin, M.P. Brandon, M.E.G. Lyons, Redox and electrochemical water splitting catalytic properties of hydrated metal oxide modified electrodes, Physical Chemistry Chemical Physics 15 (2013) 13737-13783.
[88] S. Giménez, J. Bisquert, Photoelectrochemical Solar Fuel Production: From Basic Principles to Advanced Devices, Springer International Publishing2016.
[89] T. Shinagawa, A.T. Garcia-Esparza, K. Takanabe, Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion, Scientific Reports 5 (2015) 13801.
[90] E. Fabbri, A. Habereder, K. Waltar, R. Kotz, T.J. Schmidt, Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction, Catalysis Science & Technology 4 (2014) 3800-3821.
[91] M. Tahir, L. Pan, F. Idrees, X. Zhang, L. Wang, J.-J. Zou, Z.L. Wang, Electrocatalytic oxygen evolution reaction for energy conversion and storage: A comprehensive review, Nano Energy 37 (2017) 136-157.
[92] X. Lu, C. Zhao, Electrodeposition of hierarchically structured three-dimensional nickel–iron electrodes for efficient oxygen evolution at high current densities, Nature Communications 6 (2015) 6616.
[93] X. Li, F.C. Walsh, D. Pletcher, Nickel based electrocatalysts for oxygen evolution in high current density, alkaline water electrolysers, Physical Chemistry Chemical Physics 13 (2011) 1162-1167.
[94] X. Zhang, H. Xu, X. Li, Y. Li, T. Yang, Y. Liang, Facile Synthesis of Nickel–Iron/Nanocarbon Hybrids as Advanced Electrocatalysts for Efficient Water Splitting, ACS Catalysis 6 (2016) 580-588.
[95] B. Li, S. Chen, J. Tian, M. Gong, H. Xu, L. Song, Amorphous nickel-iron oxides/carbon nanohybrids for an efficient and durable oxygen evolution reaction, Nano Research 10 (2017) 3629-3637.
[96] R. Li, J. Xu, J. Ba, Y. Li, C. Liang, T. Tang, Facile synthesis of nanometer-sized NiFe layered double hydroxide/nitrogen-doped graphite foam hybrids for enhanced electrocatalytic oxygen evolution reactions, International Journal of Hydrogen Energy 43 (2018) 7956-7963.