Effect of Lattice Structure of Bismuth Sesquioxide on the Electrochemical Energy Storage Characteristics

• Published in: Meeting abstracts (Electrochemical Society) Vol. MA2018-01; no. 44; p. 2555
• Main Authors: Kersten, Bethany R, Zillinger, James, Utgikar, Vivek, Day, Brandon, Raja, Krishnan S.
• Format: Journal Article
• Language: English
• Published: 13.04.2018
• ISSN: 2151-2043; 2151-2035
• DOI: 10.1149/MA2018-01/44/2555

Bismuth sesquioxide (Bi 2 O 3 ) exists in different polymorphs such as monoclinic α phase, tetragonal β phase, face centered cubic ( fcc ) δ phase, and body centered cubic ( bcc ) γ phase. The stable phase at room temperature is α- phase, and at temperatures between 729-824 °C the δ phase is stable. Other phases are metastable which transform from the δ phase during the cooling cycle. The metastable phases can be stabilized at room temperature either by doping with aliovalent cations in the Bi 2 O 3 lattice or by controlling the synthesis parameters. Bi 2 O 3 polymorphs are used in several engineering applications such as electrode materials for sensors, photocatalysts, and solid state electrolytes for fuel cells. Furthermore, Bi 2 O 3 is a building block for advanced ferroelectric, and multiferroic materials. Our modeling calculations suggest that β-Bi 2 O 3 could show auxetic behavior in certain crystallographic planes. Bi 2 O 3 has been investigated as a potential supercapacitor electrode material because of its promising theoretical specific capacitance (1370 F/g). Depending on the morphology and the matrix in which a composite structure was formed, the reported capacity varied from 94 – 332 F/g [[1], [2]]. Most of the investigations focused on the morphology of the Bi 2 O 3 or the composite structure of the electrode. The investigated material was either alpha [[3]] or delta phase [[4]], but no particular attention was given to the crystal structure. The effect of the lattice structure of the Bi 2 O 3 on the energy storage properties was not investigated in detail to the best of our knowledge. A recent report focused on the engineered lattice defects to enhance the capacitance [4]. In this presentation, the results of electrochemical energy storage behavior of Bi 2 O 3 electrodes prepared in the form of pure α-phase, a mixture of α+β, β-phase, and δ by electrodeposition will be reported. The α-Bi 2 O 3 thin film specimens were electrodeposited on to ITO-coated glass surfaces under galvanostatic condition at +5 mA/cm 2 in a 100 ml solution containing 0.1 M bismuth nitrate, 0.2 M tartaric acid, and NaOH to adjust the pH to 12.0 at room temperature. In order to obtain β-Bi 2 O 3 deposition, 0.05 M of Na 2 Cr 2 O 7 was added to the solution used for electrodepositing the α-phase and the electrodeposition was carried out under galvanostatic condition at 45 °C. Thin film electrodeposits with mixed α+β phases were obtained by varying the dichromate concentration in the electrolyte. The δ-Bi 2 O 3 was obtained by using a pH:14 solution containing bismuth salt on to a fcc lattice substrate (austenitic stainless steel) at 65 °C, following a similar procedure reported by Helfen et al. [[5]]. Cyclic voltammetry, and galvanostatic charge-discharge experiments were carried out on the thin film Bi 2 O 3 specimens in 0.5 M LiCl + 0.1 M NaOH solution at room temperature. The β-Bi 2 O 3 specimens showed significantly higher specific capacitance than the α-Bi 2 O 3 . The electrochemical behavior of different phases will be discussed based on the impedance spectroscopy, and Mott-Schottky results before and after charge-discharge cycles. [1] S. X. Wang, C. C. Jin, W. J. Qian, J. Alloys Compd. 2014 , 615 , 12 [2] M. Ciszewski, A. Mianowski, P. Szatkowski, G. Nawrat, J. Adamek, Ionics 2015 , 21 , 557. [3] S.T. Senthilkumar, R. Kalai Selvan, M. Ulaganathan, J.S. Melo, Electrochimica Acta 115 (2014) 518– 524 [4] R. Liu, L. Ma, G. Niu, X.-L. Li, E. Li, Y.Bai, G. Yuan, Adv. Funct. Mater. 2017 , 27 , 1701635 [5] A. Helfen et al., Solid State Ionics 176 (2005) 629–633