NANOSYSTEMS: PHYSICS, CHEMISTRY, MATHEMATICS, 2018, 9 (5), P. 669–675 Electrocatalytic properties of γ -NiOOH nanolayers, synthesized by successive ionic layer deposition, during the oxygen evolution reaction upon water splitting in the alkaline medium A.A. Lobinsky, V.P. Tolstoy, I.A. Kodinzev Institute of Chemistry, Saint Petersburg State University, 26 University Pr., St. Peterhof, Saint Petersburg, 198504, Russia lobinsky.a@gmail.com, v.tolstoy@spbu.ru, i.a.kod@mail.ru PACS 82.65+r DOI 10.17586/2220-8054-2018-9-5-669-675 Nickel oxyhydroxide nanolayers were synthesized on the surface of nickel foam and single crystalline silicon through Successive Ionic Layer Deposition (SILD) method by using aqueous solutions NiSO 4 and K 2 S 2 O 8 . The obtained nanolayers were characterized by SEM, XRD, FTIR and XPS spectroscopy. The electrochemical properties of the electrodes were defined from polarization curves. SEM images revealed that nanolayers are formed by nanosheets with a thickness of 6 – 10 nm. The nanolayers were shown to exhibit electrocatalytic properties during the oxygen evolution reaction upon water splitting in the alkaline medium. By setting the number of SILD cycles, these properties can be changed precisely. For a number of samples, synthesized after 30 – 120 SILD cycles, it was found that in the oxygen evolution reaction the lowest overpotential value of 260 mV and the lowest Tafel slope of 54 mV/dec are achieved for the sample, synthesized after 90 SILD cycles. Keywords: NiOOH, nanolayers, SILD, oxygen evolution reaction. Received: 21 August 2018 1. Introduction One of the practical approaches to hydrogen production is the splitting of water. Recently it has grown in importance due to the development of new methods for energy conservation, including renewable ones. The method of energy conservation during electrolytic water splitting allows working the problems of cyclicity and instability of energy receiving in solar and wind power areas as well as those of free capacity use during periods of no peak hours, for instance, in the nuclear power field. One of the significant features of the energy conversion is its environmental friendliness, since this process only requires water and electricity. Today it is important to reduce energy consumption for water electrolysis in such devices through overpotential reduction on the electrodes which is caused by using specific electrocatalysts. Even having been developing for more than 40 years, the history of these electrocatalysts has recently gained interest due to production of new electrocatalysts, composed of generally available transition metals such as Ni, Co and Fe [1–3]. It was mentioned [4] that catalysts based on nickel oxides or hydroxides, exhibiting high stability to oxidation in alkaline medium, are among the best. Taking into account the practical importance of challenges to synthesize electrocatalysts, to date, a variety of methods of preparative inorganic chemistry has been used. The methods had been previously tested by producing a wide range of other metal-oxygen compounds. Such methods include, for example, sol-gel [5], hydrothermal [6], coprecipitation [7], electrochemical [8] etc. Meanwhile, analysis of the literature reveals that there are few works describing Layer-by-Layer (LbL) syn- thesis as method to obtain such electrocatalysts. These include, for example, the works, devoted to the synthesis of electrocatalytic layers IrO 2 [9] and Co 3 O 4 [10]. This method of synthesis based on a successive and multiple treatments of substrate in salt or colloidal solutions and polyelectrolytes, forming an insoluble nanolayers of new compound upon interaction at the surface. The SILD method is one of LbL synthesis methods without the using of polyelectrolite solutions. We believe there are particular advantages in using SILD synthesis to create highly efficient electrocatalysts: the possibility to deposit nanolayers with a precisely defined thickness onto the surface of the electrodes of complex shape, producing such nanolayers under ”soft chemistry” conditions almost at room temperature, the use of diluted and available metal salts solutions in synthesis, etc. These features of the SILD syn- thesis had defined its efficiency, for example, when creating new supercapacitor electrodes [11], superparamagnetic materials [12], sensors active elements [13], etc. The purpose of this work is to study the electrocatalytic properties of γ -NiOOH nanolayers, synthesized by SILD method using the previously proposed synthesis scheme with salts NiSO 4 and K 2 S 2 O 8 [14], for the oxygen evolution reaction upon water splitting in the alkaline KOH solution.