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金属学报  2022, Vol. 58 Issue (10): 1292-1304    DOI: 10.11900/0412.1961.2021.00132
  研究论文 本期目录 | 过刊浏览 |
利用ZrO2 固体电解质研究Na3AlF6-SiO2 熔盐中的电沉积
高运明1,2(), 何林1,2, 秦庆伟1,2, 李光强1,2
1.武汉科技大学 省部共建耐火材料与冶金国家重点实验室 武汉 430081
2.武汉科技大学 钢铁冶金及资源利用省部共建教育部重点实验室 武汉 430081
ZrO2 Solid Electrolyte Aided Investigation on Electrodeposition in Na3AlF6-SiO2 Melt
GAO Yunming1,2(), HE Lin1,2, QIN Qingwei1,2, LI Guangqiang1,2
1.The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
2.Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China
引用本文:

高运明, 何林, 秦庆伟, 李光强. 利用ZrO2 固体电解质研究Na3AlF6-SiO2 熔盐中的电沉积[J]. 金属学报, 2022, 58(10): 1292-1304.
Yunming GAO, Lin HE, Qingwei QIN, Guangqiang LI. ZrO2 Solid Electrolyte Aided Investigation on Electrodeposition in Na3AlF6-SiO2 Melt[J]. Acta Metall Sin, 2022, 58(10): 1292-1304.

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摘要: 

利用Y2O3稳定的ZrO2固体电解质(YSZ)管集成构建Pt, O2(air)|YSZ作为参比、辅助电极的三电极新型电化学池,在完全无碳和1323 K条件下采用Ir丝作工作电极对Na3AlF6-5%SiO2 (质量分数)熔盐体系进行循环伏安(CV)及恒电位电解测试,并结合热力学理论计算、SEM观察及EDS分析,研究了熔盐中有关金属在阴极上的析出电位及电沉积规律。结果表明,Si单质在Ir电极上可一步沉积得到,其在CV曲线上的峰电位在-1.65 V,而Al、Na (Zr)等合金化沉积电位负于-1.8 V,且沉积电位依次负向增大。在-1.8 V或-2.0 V电位下电解,还发现有Zr5Si4金属化合物颗粒生成,其生成电位在-1.7~-1.8 V之间。沉积的Si、Al、Na金属(合金)主要来源于Na3AlF6-SiO2熔盐本身产生的含氧化合物,而沉积的Zr源于Na3AlF6基熔盐对YSZ管的侵蚀产生的ZrO2。有关金属(或金属化合物)相对于Pt, O2(air)|YSZ参比电极的析出电位与热力学计算较为吻合。

关键词 SiSiO2冰晶石ZrO2固体电解质电沉积    
Abstract

Electrodeposition of silicon from a cryolite-based melt is a possible solution for the mass production of silicon with high purity. Currently, deposition of Si from dissolved SiO2 in cryolite-based melts occurs primarily in a graphite crucible using graphite and quasi-reference electrodes, resulting in series of problems, such as CO x emissions due to carbon participation, non-significant peak positions on cyclic voltammetry (CV) curves due to melt electronic conduction, various reference standards of metal deposition potential, and insufficient investigations on electrode reaction mechanism due to melt composition complexity. In this work, a novel three-electrode electrochemical cell with Pt, O2(air)|YSZ reference (RE), and counter electrodes (CE) was constructed using a Y2O3 stabilized ZrO2 solid electrolyte (YSZ) tube, CV and potentiostat electrolysis tests were performed on Ir wire working electrode in Na3AlF6-5%SiO2 (mass fraction) melt under the conditions of a complete carbon-free and 1323 K. The precipitation potentials of related metals on the cathode in the melt were investigated, and the electrodeposition law in the melt at different potentials was analyzed, using a combination of thermodynamic theoretical calculations, SEM observation, and EDS analysis. The results show that Si can be deposited on the Ir wire in a single step, and its peak potential is about -1.65 V on the CV curve, while the deposition potentials of Al, Na (Zr) are all negative than -1.8 V and increase negatively in turn. During potentiostatic electrolysis, intermetallic compound particles of Zr5Si4 are observed to generate at -1.8 V or -2.0 V, with a generation potential of -1.7 V to -1.8 V. The deposited Si, Al, and Na metals are mainly derived from oxygen-containing compounds produced by the Na3AlF6-SiO2 melt itself but Zr metal from the ZrO2 of the corrosion of YSZ tubes by the melt. The precipitation potentials of related metals (or intermetallic compounds) relative to Pt, O2(air)∣YSZ RE agree well with thermodynamic calculations.

Key wordssilicon    silica    cryolite    zirconia solid electrolyte    electrodeposition
收稿日期: 2021-03-21     
ZTFLH:  TF89  
基金资助:国家自然科学基金项目(51174148)
作者简介: 高运明,男,1969年生,教授,博士
图1  电化学池装置示意图
图2  1323 K温度下Na3AlF6-5%SiO2熔盐的开路电位随时间变化曲线
No.Chemical reactionΔGΘ / (kJ·mol-1)EΘ / VE / V
12Fe + 1.5O2 = Fe2O3-4830.84-0.79
23Fe + 2O2 = Fe3O4-6960.90-0.86
32Fe + O2 = 2FeO-3580.93-0.88
44Na(g) + O2 = 2Na2O-4291.11-1.07
5Si + O2 = SiO2-6751.75-1.70
62Al + 1.5O2 = Al2O3-12552.17-2.12
7Zr + O2 = ZrO2-8422.18-2.13
82Y + 1.5O2 = Y2O3-15242.63-2.59
9Zr5Si4 + 5O2 = 4Si + 5ZrO2-35501.84-1.79
10Zr5Si4 + 9O2 = 4SiO2 + 5ZrO2-62481.80-1.75
表1  相关氧化物的化学反应式以及1323 K温度下的标准Gibbs能(ΔGΘ)和电位等数据[33]
图3  Na3AlF6-SiO2熔盐在Ir电极的循环伏安曲线
图4  Na3AlF6-SiO2熔盐恒电位电解时电流随时间变化
图5  纯Na3AlF6熔盐在-2.2 V电解后电极横断面及其附近和YSZ管底部沉积物的SEM像
PointMass fraction / %Possible phase
(atomic fraction / %)
OIrZrAu
125.9774.03ZrO2
(66.67)(33.33)
23.5680.2516.19Zr + ZrO2
(18.79)(74.27)(6.94)
325.9774.03ZrO2
(66.67)(33.33)
480.863.8015.35Ir-Zr
(77.87)(7.71)(14.42)
579.348.1812.48Ir-Zr
(72.96)(15.84)(11.20)
683.6316.37Ir
(83.97)(16.03)
725.9774.03ZrO2
(66.67)(33.33)
表2  对应于图5中各点位的EDS结果
图6  Na3AlF6-5%SiO2熔盐在不同电位电解后电极Ir丝断面的SEM像及线扫描结果
PointMass fraction of element / %Possible phase
(atomic fraction / %)
OIrZrSiAlFeAu
17.6119.4332.851.7638.36Fe-Ir, ZrO2
(40.88)(8.69)(30.97)(2.71)(16.75)
255.5644.44Ir
(56.16)(43.84)
372.671.3113.2212.79Fe-Si-Ir
(52.04)(6.44)(32.58)(8.94)
448.141.8250.04Ir-Si
(43.99)(11.39)(44.62)
548.742.3748.89Ir-Si
(43.27)(14.37)(42.35)
642.816.0251.16Ir-Si
(31.96)(30.77)(37.27)
744.3311.8143.86Zr5Si4
(43.04)(37.24)(19.72)
840.302.596.901.1749.04Si x Al y Zr z Ir m
(27.01)(3.66)(31.64)(5.61)(32.08)
944.835.450.3249.40Si x Al y Ir z
(33.80)(28.13)(1.73)(36.34)
1039.006.986.140.2247.66Si x Al y Zr z Ir m
(27.12)(10.22)(29.24)(1.07)(32.35)
1144.515.620.3849.50Si x Al y Ir z
(33.22)(28.70)(2.02)(36.05)
表3  对应于图6中各点位的EDS结果
图7  不同电位电解后的Ir丝电极与熔盐界面附近的SEM像
PointMass fraction of element / %Possible phase
(atomic fraction / %)
ZrSiAuO
174.0325.97ZrO2
(33.33)(66.67)
274.0325.97ZrO2
(33.33)(66.67)
341.7711.1541.39Zr5Si4(s)
(29.77)(25.82)(13.66)
440.1611.0742.32Zr5Si4(s)
(27.76)(24.84)(13.55)
542.1111.4640.46Zr5Si4(s)
(29.36)(25.95)(13.07)
641.8610.8540.07Zr5Si4(s)
(27.82)(23.41)(12.33)
表4  对应于图7中各点位的EDS结果
图8  Zr和Zr5Si4的氧化反应的标准Gibbs自由能ΔGΘ与温度T的关系
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