Computer-aided control of electrolysis of solid Nb2O5 in molten CaCl2.
Low energy production of Nb powders via computer-aided control (CAC) of two-electrode electrolysis of porous Nb2O5 pellets (ca. 1.0 g) has been successfully demonstrated in molten CaCl2 at 1123 K. It was observed that potentiostatic electrolysis of the oxide in a three-electrode cell led to a cell voltage, i.e. the potential difference between the working (cathode) and counter (anode) electrodes, that decreased to a low and stable value within 1-2 h of the potential application until the end of the electrolysis (up to 12 h in this work). The cell voltage varied closely according to the current change. The stabilised cell voltage was below 2.5 V when the cathode potential was more positive than that for the reduction of Ca2+, leading to much lower energy consumption than that of constant voltage (>3.0 V) two-electrode electrolysis, as previously reported. Using a computer to program the variation of the cell voltage of two-electrode electrolysis according to that observed in the potentiostatic three-electrode electrolysis (0.05 V vs. Ca/Ca2+), a Nb powder with ca. 3900 ppm oxygen was produced in 12 h, with the energy consumption being 37.4% less than that of constant voltage two-electrode electrolysis at 3.0 V. Transmission electron microscopy revealed thin oxide layers (4-6 nm) on individual nodular particles (1-5 microm) of the obtained Nb powder. The oxide layer was likely formed in post-electrolysis processing operations, including washing in water, and contributed largely to the oxygen content in the obtained Nb powder.
Wu
Tian
T
College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, P. R. China.
Xiao
Wei
W
Jin
Xianbo
X
Liu
Chao
C
Wang
Dihua
D
Chen
George Z
GZ
D002122:Calcium Chloride / Q000737:chemistry*; D003201:Computers; D004563:Electrochemistry / Q000379:methods; D004572:Electrolysis; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D009556:Niobium / Q000032:analysis / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D011199:Potentiometry; D011208:Powders; D012984:Software; D014961:X-Ray Diffraction
D010087:Oxides; D011208:Powders; D009556:Niobium; D002122:Calcium Chloride; D010100:Oxygen