Anal. Chem. 1998, 70, 1007-1011
Airtight in Situ Thin-Layer Reflection-Absorption FT-IR Microspectroelectrochemical Cell for the Study of Nonaqueous Systems Marı´a Enid Rosa-Montan˜ez,† He´ctor De Jesu´s-Cardona,‡ and Carlos R. Cabrera-Martı´nez*,†
Departamento de Quı´mica, Universidad de Puerto Rico, Recinto de Rı´o Piedras, Apartado 23346, San Juan, Puerto Rico 00931-3346, and Departamento de Quı´mica, Universidad de Puerto Rico, Colegio Universitario Tecnolo´ gico de Bayamo´ n, 170 Carretera 174, Parque Industrial Minilla, Bayamo´ n, Puerto Rico 00959
An airtight thin-layer reflection FT-IR microspectroelectrochemical cell suitable for the study of both aqueous and nonaqueous electrochemical systems is described. Due to its design, the cell can be easily assembled using disk microelectrodes. This variable-thickness cell can be used for the voltammetric study of both aqueous and nonaqueous systems under semi-infinite diffusion and thin-layer conditions. Dichloromethane solutions of ferrocene were used to test the in situ FT-IR microspectroelectrochemical performance of the cell. The cyclic voltammetric behavior of an oxygen- and water-free CH2Cl2 solution of Ru3(CO)12, under semi-infinite diffusion conditions, provides evidence of the airtightness of this cell. The coupling of FT-IR microspectroscopy with in situ FT-IR thin-layer reflection-absorption spectroelectrochemistry by Lin and co-workers has recently led to the development of in situ thinlayer reflection-absorption FT-IR microspectroelectrochemistry (FTIRMSEC).1-4 In this spectroelectrochemical technique, the cell is placed on the stage of an FT-IR microscope, and the working electrode surface is directly focused with the aid of the microscope. FT-IR reflection-absorption spectra of the solution sandwiched between the infrared transparent window and the electrode surface (thin-layer chamber) are recorded while the electrode is held at an appropriate applied potential. Several applications of in situ FT-IR microspectroelectrochemistry have been published by Lin’s research group.1-4 However, since their studies have been focused on aqueous systems, the particular needs of nonaqueous systems have not been addressed in their cell designs. For example, electrode assemblies and IRtransparent windows are fixed with epoxy resins which are susceptible to attack by nonaqueous solvents.5-7 Also, drilled †
Recinto de Rı´o Piedras. Colegio Universitario Tecnolo´gico de Bayamo´n. (1) Lin, X. Q.; Li, Z. L. Chin. Chem. Lett. 1992, 3, 1029. (2) Lin, X. Q.; Zhang, H. Q. Fenxi Huaxue 1993, 21, 1355. (3) Lin, X. Q.; Li, Z. L. Chin. Chem. Lett. 1993, 4, 355. (4) Li, Z. L.; Lin, X. Q. J. Electroanal. Chem. 1995, 386, 83. (5) Nevin, W. A.; Lever, A. B. P. Anal. Chem. 1988, 60, 727. (6) Stole, S. M.; Popenoe, D. D.; Porter, M. D. In Electrochemical Interfaces: Modern Techniques for In Situ Interface Characterization; Abrun ˜a, H. D., Ed.; VCH Publishers, Inc.: New York, 1991; p 339. ‡
S0003-2700(97)00416-2 CCC: $15.00 Published on Web 02/03/1998
© 1998 American Chemical Society
windows are used as the solution inlet and outlet ports, leading to the evaporation of volatile solvents and to the interference of environmental oxygen and moisture in the analysis. Therefore, to exploit the potential of this new spectroelectrochemical technique, a cell that allows the study of both aqueous and nonaqueous electrochemical systems is needed. In this paper, we present an airtight in situ thin-layer reflection-absorption FTIRMSEC cell, specially suitable for the study of nonaqueous electrochemical systems. EXPERIMENTAL SECTION Materials. Potassium chloride (MCB, ACS grade), K3Fe(CN)6 (Aldrich, 99%), CH2Cl2 (Fluka, >99.5%, H2O
