Ni(II) doped FeOOH 2D nanocrystals, synthesized by Successive Ionic Layer Deposition, and their electrocatalytic properties during oxygen evolution reaction upon water splitting in the alkaline medium

Abstract

Nanolayers of Ni(II) doped FeOOH 2D nanocrystals were for the first time synthesized on the surface of nickel foam and single crystalline silicon wafer through Successive Ionic Layer Deposition (SILD) method by using an aqueous solution of Fe(NH4)2(SO4)2 with the equilibrium pH value, as well as the solution containing Ni(NO3)2 and NH4NO3 with pH = 9.5 reached by addition of ammonia. The obtained nanolayers were investigated by SEM, HRTEM, TEM, EDX, XRD, XPS and FTIR spectroscopy. They were stated to be formed by Ni:FeOOH 2D nanocrystals with lepidocrocite and goethite crystal structures having the morphology of nanosheets. They are 2–5 nm thick with planar dimensions of about 30–50 nm and the ratio of atomic concentrations of Ni to Fe is 25%. The nanolayers were shown to exhibit electrocatalytic properties during the oxygen evolution reaction upon water splitting in the alkaline medium. For the first time it was shown that the overpotential value can be precisely set by varying the number of SILD cycles these properties can be changed precisely. For a number of samples, synthesized after 20–80 SILD cycles, it was found for a current density of 10 mA/cm2 the lowest overpotential value of 239 mV was obtained for the sample synthesized after 60 SILD cycles. The synthesis of a wide range of electrocatalytic nanolayers by SILD with the precise structural and chemical characteristics was suggested.