ELECTROCHEMICAL CHARACTERIZATION OF THE CARBON PASTE ELECTRODE MODIFIED WITH BATIO3 W. B. S. Machini1, R. S. Magalhães1, M. F. S. Teixeira1, S. R. Teixeira1, A. E. Souza1, C. X. Cardoso1, E. Longo2 1Universidade Estadual Paulista-UNESP, Faculdade de Ciências e Tecnologia, Presidente Prudente, SP; 2UNESP, Instituto de Química, Araraquara, SP, Brazil; e-mail:
[email protected]
Introduction Barium titanate (BaTiO3) has a cubic perovskite structure and exhibits a semiconducting behavior, high dielectric constant, good thermal and structural stability. Due to its chemical and physical properties it has a broadly range of applications and is widely studied. Electrochemical analysis, such as cyclic voltammetry and impedance spectroscopy, are important to understand the behavior of semiconductors. In this work it was studied the electrochemical behavior of the carbon paste electrode modified with BaTiO3 (CPEM-BaTiO3) by cyclic voltammetry in HCl solution.
Materials and Methods
Results – BTO Powder Characterization Figure 1: XRD of BTO sample: Barium titanate and anatse (TiO2).
Barium Titanate (BTO) Synthesis The BTO was synthesized using the hydrothermal method assisted by microwave (HMA) . Rate of heating of 140°C min-1, reaction temperature around 140°C and 40 min residence time. Chemical Precursors: BaCl, a complex Anatase-H2O2 (30%) and KOH (1 mol L-1 solution), as mineralizer.
Figure 2: BTO FE-SEM imagens: aglomerates and nanoparticles.
BTO – Characterization XRD – X-ray Diffraction SEM – Scanning Electron Microscopy
Construction of the carbon paste (weight%)) electrode modified with BaTiO3 (CPEM-BaTiO3) 10% - BaTiO3 + 60% - Graphite power + 30% - Mineral oil
Results – Electrochemical properties of the CPEM-BaTiO3 • Cyclic voltammogram reveals a quasi-reversible system with one redox process (Epa = 0.513 V and Epc = 0.387 V vs. SCE), being the peak-to-peak separation (ΔEp) and half potential (Ep/2) of 0.450 V and 0.126 V vs. SCE, respectively. • The cyclic voltammograms exhibit an increase of anodic and cathodic peak current as the scan rate increases. • The plot of current (µA) by square root of the scan rate (mV s-1)1/2 gives a linear correlation, suggesting that the redox process follows a diffusion-controlled mechanism. • This behavior indicates that the charge transfer reaction of BaTiO3 is controlled by diffusion of protons in the solid phase. • The concentration of electroactive species was found to be 13.992 nmol cm-2 (for 20 mV s-1). • Based on these results it was possible to understand the electrochemical behavior of CPEM-BTO, which showed up promising in the development of an electrochemical sensor for protons.
Magnetic stirring in a 50 mL beaker containing 20 mL of hexane solvent evaporation Electroactive material was packed into an electrode body (plastic cylindrical tube with a stainless steel electric contact) Electrochemical measurements 15 10
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a) Cyclic voltammetry: Potentiostat/galvanostat μ-Autolab Type III (Eco Chimie); b) Thermostated electrochemical cell with three electrodes: 1) Pt wire (auxiliary); 2) Saturated calomel electrode (SCE) (reference); 3) CPEM-BaTiO3 - working electrode (area = 0.2826 cm2); c) Electrolytic solution: HCl 0.01 mol L-1; d) Potential scans rates (5 to 100 mV s-1).
Epa = 0.513
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Figure 1: (a) Cyclic voltammogram for the CPEM-BaTiO3 in HCl 0.01 mol L-1 solution from 0.0 to 0.9 vs. SCE at 20 mV s-1, (b) at different scan rates and (c) Dependence of the current on square root of the scan rate for the CPEM-BaTiO3.
Acknowledgement
