Journal of Applied Electrochemistry

, Volume 49, Issue 8, pp 743–753 | Cite as

Evaluation of overpotentials on graphite and liquid Bi–Mg electrodes by current interruption

  • Kazuhiro KumamotoEmail author
  • Akihiro Kishimoto
  • Tetsuya UdaEmail author
Research Article
Part of the following topical collections:
  1. Electrochemical Processes


Our group proposes a new titanium smelting process via Bi–Ti alloy. This process is comprised of reduction of TiCl4 by Bi–Mg liquid alloy, separation of Ti from Bi by distillation, and Mg electrolysis. In this study, the Mg electrolysis with Bi–Mg liquid alloy cathode was investigated. We firstly measured the IR-corrected polarization curves on graphite and Bi–Mg liquid alloys by the current interruption method. The results indicated that the Bi–Mg alloy cathode can reduce the electricity consumption of the Mg electrolysis. In addition, from the relaxation curves on graphite and Bi–Mg alloys, the concentration overpotential on the Bi–Mg alloy is mainly due to mass transfer of Mg from the electrode/molten salt interface to the liquid alloy bulk. At current densities higher than 300 mA cm−2, Mg-rich solid phases such as Bi2Mg3 and/or pure solid Mg are assumed to be deposited on the Bi–Mg liquid alloy cathode. Finally, we estimated the electricity consumption of the Mg electrolysis in the new smelting process based on the measured overpotentials, assuming that Bi–Mg liquid alloy cathode is stirred sufficiently and a low current density, 275 mA cm−2, is applied. Under these conditions, the total electricity consumption of the Mg electrolysis in the new process will be lower than that in the Kroll process when the anode–cathode distance is smaller than 8 cm.

Graphic abstract

IR-corrected polarization curves of (a) Mg2+ reduction on graphite and Bi–Mg liquid alloys and (b) Cl2 evolution on graphite in MgCl2–NaCl–KCl at 550 °C were measured by the current interruption method, and electricity consumption of Mg electrolysis in the new Ti smelting process was estimated from these results.


Molten salt Overpotentials Magnesium electrolysis Bi–Mg alloy 



This work was supported by Advanced Low Carbon Technology Research and Development Program, Japan Science and Technology Agency, JST ALCA (Grant No. JPMJAL1006). Bi metal was supplied by Kamioka Mining & Smelting Co., Ltd.


  1. 1.
    Kroll W (1940) The production of ductile titanium. J Electrochem Soc 78:35–47. CrossRefGoogle Scholar
  2. 2.
    Chen GZ, Fray DJ, Farthing TW (2000) Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature 407:361–364. CrossRefGoogle Scholar
  3. 3.
    Ono K, Suzuki RO (2002) A new concept for producing Ti sponge: calciothermic reduction. JOM 54:59–61. CrossRefGoogle Scholar
  4. 4.
    Crowley G (2003) How to extract low-cost titanium. Adv Mater Process 161:25–27Google Scholar
  5. 5.
    Takeda O, Okabe TH (2006) High-speed titanium production by magnesiothermic reduction of titanium trichloride. Mater Trans 47:1145–1154. CrossRefGoogle Scholar
  6. 6.
    Okabe TH, Oda T, Mitsuda Y (2006) Titanium powder production by preform reduction process (PRP). J Alloys Compd 364:156–163. CrossRefGoogle Scholar
  7. 7.
    Zhang Y, Fang ZZ, Xia Y, Huang Z, Lefler H, Zhang T, Sun P, Free ML, Guo J (2016) A novel chemical pathway for energy efficient production of Ti metal from upgraded titanium slag. Chem Eng J 286:517–527. CrossRefGoogle Scholar
  8. 8.
    Maruyama S, Kado Y, Uda T (2013) Phase diagram investigations of the Bi–Ti system. J Phase Equilib Diffus 34:289–296. CrossRefGoogle Scholar
  9. 9.
    Kado Y, Kishimoto A, Uda T (2015) New smelting process for titanium: magnesiothermic reduction of TiCl4 into liquid Bi and subsequent refining by vacuum distillation. Metall Mater Trans B 46:57–61. CrossRefGoogle Scholar
  10. 10.
    Kishimoto A, Kado Y, Uda T (2016) Electrorefining of titanium from Bi–Ti alloys in molten chlorides for a new smelting process of titanium. J Appl Electrochem 46:987–993. CrossRefGoogle Scholar
  11. 11.
    Kishimoto A, Kuramitsu A, Tsuchihashi K, Uda T (2016) Continuous production of Bi–Ti alloys by magnesiothermic reduction of TiCl4 for a new smelting process of Ti. J MMIJ 123:199–206. CrossRefGoogle Scholar
  12. 12.
    Kishimoto A, Uda T (2018) Thermodynamics on the Bi–Fe–Ti system and the gibbs energy of Bi9Ti8. Metall Mater Trans B 49:2975–2985. CrossRefGoogle Scholar
  13. 13.
    Tomonari T (2001) Chitan Kogyo to Sono Tenbo. The Japan Titanium Society, JapanGoogle Scholar
  14. 14.
    Furihata S, Akashi K, Kurosawa S (1981) The polarographic reduction wave of magnesium ion(II) in a molten LiCl–KCl eutectic mixture. Electrochim Acta 26:1107–1109. CrossRefGoogle Scholar
  15. 15.
    Rao GM (1988) Electrochemical studies of magnesium ions in magnesium chloride containing chloride melt at 710 ± 10 °C. J Electroanal Chem 249:191–203. CrossRefGoogle Scholar
  16. 16.
    Kisza A, Kaźmierczak J, Børresen B, Haarberg GM, Tunold R (1995) Kinetics and mechanism of the magnesium electrode reaction in molten magnesium chloride. J Appl Electrochem 25:940–946. CrossRefGoogle Scholar
  17. 17.
    Kisza A, Kaźmierczak J, Børresen B, Haarberg GM, Tunold R (1997) Kinetics and mechanism of the magnesium electrode reaction in molten MgCl2–NaCl binary mixtures. J Electrochem Soc 144:1646–1651. CrossRefGoogle Scholar
  18. 18.
    Børresen B, Haarberg GM, Tunold R (1997) Electrodeposition of magnesium from halide melts—charge transfer and diffusion kinetics. Electrochim Acta 42:1613–1622. CrossRefGoogle Scholar
  19. 19.
    Martínez AM, Børresen B, Haarberg GM, Castrillejo Y, Tunold R (2004) Electrodeposition of magnesium from CaCl2–NaCl–KCl–MgCl2 melts. J Electrochem Soc 151:C508–C513. CrossRefGoogle Scholar
  20. 20.
    Moser Z, Krohn C (1974) Thermodynamic properties of liquid magnesium–bismuth alloys. Metall Trans 5:979–985. CrossRefGoogle Scholar
  21. 21.
    Nayeb-Hashemi AA, Clark JB (1985) The Bi-Mg (bismuth–magnesium) system. Bull Alloys Phase Diag 6:528–533. CrossRefGoogle Scholar
  22. 22.
    Kosemura S, Ampo S, Fukasawa E, Hatta Y (2007) Production of titanium metal at Toho Titanium Co., Ltd. J MMIJ 123:693–697. CrossRefGoogle Scholar
  23. 23.
    Güden M, Karakaya İ (1994) Electrolysis of MgCl2 with a top inserted anode and an Mg–Pb cathode. J Appl Electrochem 24:791–797. CrossRefGoogle Scholar
  24. 24.
    Demirci G, Karakaya İ (2007) Collection of magnesium in an Mg–Pb alloy cathode placed at the bottom of the cell in MgCl2 electrolysis. J Alloys Compd 439:237–242. CrossRefGoogle Scholar
  25. 25.
    Leung P, Heck SC, Amietszajew T, Mohamed MR, Conde MB, Dashwood RJ, Bhagat R (2015) Performance and polarization studies of the magnesium–antimony liquid metal battery with the use of in-situ reference electrode. RSC Adv 5:83096–83105. CrossRefGoogle Scholar
  26. 26.
    Newhouse JM, Sadoway DR (2017) Charge-transfer kinetics of alloying in Mg-Sb and Li-Bi liquid metal electrodes. J Electrochem Soc 164:A2665–A2669. CrossRefGoogle Scholar
  27. 27.
    Bard AJ (1976) Encyclopedia of electrochemistry of the elements, vol 10. Marcel Dekker Inc, New YorkGoogle Scholar
  28. 28.
    Komura A, Imanaga H, Watanabe N (1971) Chlorine evolution process in magnesium chloride–potassium chloride melt. Kogyo Kagaku Zassshi 74:867–871. CrossRefGoogle Scholar
  29. 29.
    The Electrochemical Society of Japan (2000) Denki Kagaku Binran, 5th edn. Maruzen Publishing Co., Ltd, TokyoGoogle Scholar
  30. 30.
    Egan JJ, Bracker J (1974) Thermodynamic properties of some binary fused chloride mixtures obtained from e.m.f. measurements. J Chem Thermodyn 6:9–16. CrossRefGoogle Scholar
  31. 31.
    Redlich O, Kister AT (1948) Algebraic representation of thermodynamic properties and the classification of solutions. Ind Eng Chem 40:345–348. CrossRefGoogle Scholar
  32. 32.
    Papatheodorou GN, Kleppa OJ (1967) Enthalpies of mixing in some binary alkaline-earth chlorides. J Chem Phys 47:2014–2020. CrossRefGoogle Scholar
  33. 33.
    Hersh LS, Kleppa OJ (1965) Enthalpies of mixing in some binary liquid halide mixtures. J Chem Phys 42:1309–1322. CrossRefGoogle Scholar
  34. 34.
    Pelton AD (2001) A general “geometric” thermodynamic model for multicomponent solutions. CALPHAD 25:319–328. CrossRefGoogle Scholar
  35. 35.
    Dinsdale AT (1991) SGTE data for pure elements. CALPHAD 15:317–425. CrossRefGoogle Scholar
  36. 36.
    Perry GS, Fletcher H (1993) The magnesium chloride–potassium chloride phase diagram. J Phase Equilib 14:172–178. CrossRefGoogle Scholar
  37. 37.
    Chase NW Jr (1998) NIST-JANAF, thermochemical tables, 4th edn. ACS and AIP, Washington, D. C.Google Scholar

Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Department of Materials Science and Engineering, Graduate School of EngineeringKyoto UniversityKyotoJapan

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