Protsenko V

Protsenko V.S., Vasil'eva E.A., Tsurkan A.V., Danilov F.I.

Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine

Composite coatings iron/titania obtained from an electrolyte on the basis of methanesulphonic acid

Electrodeposition of composite coatings allows obtaining electrodeposits with a broad spectrum of various physicochemical and service properties [1]. Electrodeposition of composite coatings containing nanoparticles in a metal deposit is of special interest because this enables the fabrication of materials possessing a wide range of properties not available both with pure metal or alloy coatings and with composites containing larger particles entrapped [2]. In this work we investigated the electrodeposition of iron-titania composite coatings from a methanesulphonate electrolyte. Electrochemical systems on the basis of methanesulphonic acid and its salts have been shown to be very promising for electroplating of different metals, alloys and composites [3-7]. The TiO₂ particles (Degussa P25; it contains mainly anatase) with an average diameter of 25 nm were used. The bath composition and electrolysis conditions are presented in Table 1.

Table 1

Bath composition and electrolysis conditions for preparation of Fe/TiO₂ composites

Bath composition

Electrolysis conditions

1.25 mol/dm³ Fe(CH₃SO₃)₂

1-10 g/dm³ TiO₂

pH 1.3

Temperature 298 К

Current density 5-20 A/dm²

Electrolyte stirring by magnetic stirrer (60 rpm)

Electrodeposition duration 20 min

As follows from the data obtained (Figure), an increase in the cathodic current density leads to a decrease in the titania content in coatings. Such a behavior is typical of diverse types of electrodeposited composites [1, 2, 8, 9]. As would be expected, the content of TiO₂ particles in the composites increases with the titania concentration in electroplating bath.

Effect of current density on titania content in deposits.

The plating baths contained TiO₂ (g/dm³): (1) 1, (2) 2, (3) 5, (4) 10

The Fe/TiO₂ composite coatings deposited from a methanesulphonate bath are pale grey and uniform, they have a good adhesion to the copper substrate. The thickness of the composite coatings can reach several hundred micrometers. The deposition rate and the composites composition do not depend on the electrolysis duration.

It is well-known that titania exhibits high photocatalytic activity; in particular, titania is very effective in photocatalytic decomposition of various organic dyes in wastewater [9]. We evaluated the photocatalytic activity of Fe/TiO₂ composite coatings in the model reaction of decomposition of methyl orange (MO) dye in alkaline solution. According to our findings, methyl orange dye does not undergo spontaneous decomposition without UV irradiation. The photocatalytic decomposition of the dye under the action of UV radiation is accelerated in the presence of a Fe/TiO₂ catalyst. The reaction kinetics of MO degradation was stated to follow the pseudo-first rate law. The calculated formal rate constants are given in Table 2.

Table 2

Formal rate constants of the photocatalytic decomposition of methyl orange

Catalyst	Rate constants, min^-1
Without catalyst	0.0054
Fe/TiO₂ (10% wt.)	0.0135

We revealed also that the Fe/TiO₂ composite coatings exhibit enhanced electrocatalytic activity towards hydrogen evolution reaction and oxygen evolution reaction in 1 M NaOH. Thus, these coatings are to be used for development of more efficient electrocatalysts which can replace extremely expensive electrocatalytic materials containing noble metals (Pt, Ru, etc.).

References

1. Walsh F.C., Ponce de Leon C. Transactions of the Institute of Metal Finishing, 2014, vol. 92, pp. 83-98.

2. Low C.T.J., Wills R.G.A., Walsh F.C. Surface and Coatings Technology, 2006, vol. 201, pp. 371-383.

3. Walsh F.C., Ponce de Leon C. Surface and Coatings Technology, 2014, vol. 259, pp. 676-697.

4. Danilov F.I., Butyrina T.E., Protsenko V.S., Vasil'eva E.A. Russian Journal of Applied Chemistry, 2010, vol. 83, pp. 752-754.

5. Danilov F.I., Vasil'eva E.A., Butyrina T.E., Protsenko V.S. Protection of Metals and Physical Chemistry of Surfaces, 2010, vol. 46, pp. 697-703.

6. Danilov F.I., Protsenko V.S., Vasil'eva E.A., Kabat O.S. Transactions of the Institute of Metal Finishing, 2011, vol. 89, pp. 151-154.

7. Protsenko V.S., Kityk A.A., Danilov F.I. Journal of Electroanalytical Chemistry, 2011, vol. 661, pp. 213-218.

8. Protsenko V.S., Vasil'eva E.A., Smenova I.V., Baskevich A.S., Danilenko I.A., Konstantinova T.E., Danilov F.I. Surface Engineering and Applied Electrochemistry, 2015, vol. 51, pp. 65-75.

9. Protsenko V.S., Vasil'eva E.A., Smenova I.V., Danilov F.I. Russian Journal of Applied Chemistry, 2014, vol. 87, pp. 283-288.