English

Electrochemical Features of Carbon Prepared by Molten Salt Electro-Reduction of CO₂

• GU Yuxing ,
• YANG Juan ,
• WANG Dihua ^,

• Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, School of Resource and Environmental Science, Wuhan University, Wuhan 430072, P. R. China

Corresponding author: WANG Dihua, Email: wangdh@whu.edu.cn; Tel.: +86-27-68774216

• Received Date: 15 January 2018
  Accepted Date: 07 February 2018
  Revised Date: 07 February 2018
  Available Online: 15 February 2019
• Fund Project:

  The project was supported by the National Natural Science Foundation of China (21673162, 51325102) and the International Science & Technology Cooperation Program of China (2015DFA90750)

Abstract: The molten salt CO₂ capture and electrochemical transformation (MSCC-ET) process is a potentially efficient method for CO₂ utilization, which can convert CO₂ into value-added carbon and oxygen with a current density of 100–1000 mA cm^-2. The electrolytic carbon (EC) prepared through the MSCC-ET process is highly electrically conductive and forms flexible microstructures. These structures show excellent adsorption ability towards environmental pollutants and high energy storage capacity when used in supercapacitors. Although the morphology, structure, and application of EC prepared under different electrolysis conditions have been previously reported, their intrinsic electrochemical properties have not yet been elucidated. Powder microelectrodes (PMEs) are useful for studying the electrochemical kinetics of various powdery materials. In this study, we systematically investigated the electrochemical properties of ECs obtained using molten Li₂CO₃-Na₂CO₃-K₂CO₃ under different temperature and electrolysis voltage conditions by cyclic voltammetry (CV) with a carbon powder microelectrode in 10 mmol L^-1 Na₂SO₄. The electrochemical behavior of the EC obtained at 450 ℃ and a cell voltage of 4.5 V (450 ℃-4.5 V-EC) differs significantly from that of other carbon materials, i.e., multi-walled carbon nanotubes, graphene, graphite, and acetylene black. In addition to a much larger charging-discharging capacity, unusual hysteresis of the charge/discharge current response of ECs in the negative potential region (-0.6 to -0.2 V vs SCE) was observed. This phenomenon was eliminated by annealing the material under Ar at 550 ℃, demonstrating that the unique electrochemical behavior of ECs is closely related to the oxygen-containing groups on its surface. Furthermore, CVs of EC-PME were compared in solutions with different pH, Na₂SO₄ concentrations, and other ions. The pH of the solution did not affect the CVs, excluding a redox mechanism involving the surface functional groups. Hysteresis was weakened by a certain degree at slower potential sweep speeds (< 10 mV s^-1) or in higher concentrations of electrolyte (100 mmol L^-1 Na₂SO₄). The onset potential for discharging was negatively shifted in electrolytes with a larger cation ((NH₄)₂SO₄) and was unaffected by larger anions (Na₂S₂O₈). This indicates that the hysteresis is more likely related to the specific adsorption of cations, caused by the unique surface properties of EC. It should be noted that the specific surface area and oxygen concentration of EC can be adjusted by the electrolysis temperature and cell voltage. Generally, the Brunauer–Emmett–Teller (BET) specific surface area and oxygen content decrease with increasing temperature and the BET-area increases with increasing cell voltage. The CVs of ECs prepared at different cell voltages were similar, but the adsorption capacity decreased for those prepared at higher temperatures (550 and 650 ℃). Interestingly, the specific capacitance of the ECs is much higher at negative potentials (-0.6 to 0 V vs. SCE) than that at positive potentials (0 to 0.6 V vs. SCE). Therefore, it is anticipated that a better capacitance performance can be achieved when the ECs are used as a negative electrode material in supercapacitors.

Key words:
• Electrolytic-carbon
•  /  Molten salts
•  /  Powder microelectrode
•  /  Electrochemical property
•  /  Specific adsorption

• 1. [1]

     白晓芳, 陈为, 王白银, 冯光辉, 魏伟, 焦正, 孙予罕.物理化学学报, 2017, 33, 2388. doi: 10.3866/PKU.WHXB201706131Bai, X. F.; Chen, W.; Wang, B. Y.; Feng, G. H.; Wei, W.; Jiao, Z.; Sun, Y. H. Acta Phys. -Chim. Sin. 2017, 33, 2388. doi: 10.3866/PKU.WHXB201706131

  2. [2]

     Licht, S. Adv. Mater. 2011, 23, 5592. doi: 10.1002/adma.201103198

  3. [3]

     Yin, H. Y.; Mao, X. H.; Tang, D. Y.; Xiao, W.; Xing, L. R.; Zhu, H.; Wang, D. H.; Sadoway, D. R. Energy Environ. Sci. 2013, 6, 1538. doi: 10.1039/c3ee24132g

  4. [4]

     Tang, D. Y.; Yin, H. Y.; Mao, X. H.; Xiao, W.; Wang, D. H. Electrochim. Acta 2013, 114, 567. doi: 10.1016/j.electacta.2013.10.109

  5. [5]

     Kaplan, B.; Groult, H.; Barhoun, A.; Lantelme, F.; Nakajima, T.; Gupta, V.; Komaba, S.; Kumagai, N. J. Electrochem. Soc. 2002, 149, D72. doi: 10.1149/1.1464884

  6. [6]

     Ijije, H. V.; Lawrence, R. C.; Chen, G. Z. RSC Adv. 2014, 4, 35808. doi: 10.1039/c4ra04629c

  7. [7]

     Ge, J. B.; Wang, S.; Hu, L. W.; Zhu, J.; Jiao, S. Q. Carbon 2016, 98, 649. doi: 10.1016/j.carbon.2015.11.065

  8. [8]

     Ijije, H. V.; Sun, C.; Chen, G. Z. Carbon 2014, 73, 163. doi: 10.1016/j.carbon.2014.02.052

  9. [9]

     Tang, J.; Deng, B.; Xu, F.; Xiao, W.; Wang, D. J. Power Sources 2017, 341, 419. doi: 10.1016/j.jpowsour.2016.12.037

  10. [10]

      Ge, J. B.; Hu, L. W.; Wang, W.; Jiao, H. D.; Jiao, S. Q. ChemElectroChem 2015, 2, 224. doi: 10.1002/celc.201402297

  11. [11]

      Groult, H.; Kaplan, B.; Lantelme, F.; Komaba, S.; Kumagai, N.; Yashiro, H.; Nakajima, T.; Simon, B.; Barhoun, A. Solid State Ionics 2006, 177, 869. doi: 10.1016/j.ssi.2006.01.051

  12. [12]

      Mao, X. H.; Yan, Z. P.; Sheng, T.; Gao, M. X.; Zhu, H.; Xiao, W.; Wang, D. H. Carbon 2017, 111, 162. doi: 10.1016/j.carbon.2016.09.035

  13. [13]

      Novoselova, I. A.; Oliinyk, N. F.; Volkov, S. V.; Konchits, A. A.; Yanchuk, I. B.; Yefanov, V. S.; Kolesnik, S. P.; Karpets, M. V. Phys. E: Low-Dimen. Syst. Nanostruct. 2008, 40, 2231. doi: 10.1016/j.physe.2007.10.069

  14. [14]

      Song, Q.; Xu, Q.; Wang, Y.; Shang, X.; Li, Z. Thin Solid Films 2012, 520, 6856. doi: 10.1016/j.tsf.2012.07.056

  15. [15]

      Ren, J.; Li, F. F.; Lau, J.; Gonzalez-Urbina, L.; Licht, S. Nano Lett. 2015, 15, 6142. doi: 10.1021/acs.nanolett.5b02427

  16. [16]

      Deng, B. W.; Mao, X. H.; Xiao, W.; Wang, D. H. J. Mater. Chem. A 2017, 5, 12822. doi: 10.1039/c7ta03606j

  17. [17]

      Deng, B. W.; Tang, J. J.; Gao, M. X.; Mao, X. H.; Zhu, H.; Xiao, W.; Wang, D. H. Electrochim. Acta 2018, 259, 975. doi: 10.1016/j.electacta.2017.11.025

  18. [18]

      Cha, C. S.; Li, C. M.; Yang, H. X.; Liu, P. F. J. Electroanal. Chem. 1994, 368, 47. doi: 10.1016/0022-0728(93)03016-I

  19. [19]

      Zhao, Y. D.; Zhang, W. D.; Chen, H.; Luo, Q. M. Anal. Sci. 2002, 18, 939. doi: 10.2116/analsci.18.939

  20. [20]

      Zhao, Y. D.; Zhang, W. D.; Chen, H.; Luo, Q. M. Sens. Actuators B 2003, 92, 279. doi: 10.1016/s0925-4005(03)00312-5

  21. [21]

      Luo, J. W.; Zhang, M.; Pang, D. W. Sens. Actuators B 2005, 106, 358. doi: 10.1016/j.snb.2004.08.020

  22. [22]

      Zeng, R. H.; Li, W. S.; Lu, D. S.; Huang, Q. M. J. Power Sources 2007, 174, 592. doi: 10.1016/j.jpowsour.2007.06.120

  23. [23]

      Vivier, V.; Cachet Vivier, C.; Cha, C. S.; Nedelec, J. Y.; Yu, L. T. Electrochem. Commun. 2000, 2, 180. doi: 10.1016/S1388-2481(00)00004-7

  24. [24]

      Serghini Idrissi, M.; Bernard, M. C.; Harrif, F. Z.; Joiret, S.; Rahmouni, K.; Srhiri, A.; Takenouti, H.; Vivier, V.; Ziani, M. Electrochim. Acta 2005, 50, 4699. doi: 10.1016/j.electacta.2005.01.050

  25. [25]

      Rabbow, T. J.; Trampert, M.; Pokorny, P.; Binder, P.; Whitehead, A. H. Electrochim. Acta 2015, 173, 24. doi: 10.1016/j.electacta.2015.05.058

  26. [26]

      Luo, H.; Shi, Z.; Li, N.; Gu, Z.; Zhuang, Q. Anal. Chem. 2001, 73, 915. doi: 10.1021/ac000967l

  27. [27]

      Rabbow, T. J.; Whitehead, A. H. Carbon 2017, 111, 782. doi: 10.1016/j.carbon.2016.10.064

  28. [28]

      Jorgensen, T. C.; Weatherley, L. R. Water Res. 2003, 37, 1723. doi: 10.1016/s0043-1354(02)00571-7

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