Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The voltammetry and kinetics of the Ag|Ag + system (commonly used as a reference electrode material in both protic/aprotic and RTIL solvents) was studied in the room-temperature ionic liquid N-buty1-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C 4 mpyrr] [NTf 2 ] on a 10 μm diameter Pt electrode. For the three silver salts investigated (AgOTf, AgNTf 2 , and AgNO 3 , where OTf- = trifluoromethanesulfonate, NTf 2- = bis(trifluoromethylsulfonyl)imide, and NO 3- = nitrate), the voltammetry gave rise to a redox couple characteristic of a "deposition/stripping" process at the platinum electrode surface. Using potential step chronoamperometry, the diffusion coefficients of AgOTf, AgNTf 2 , and AgNO 3 were found to be 1.05, 1.17, and 5.00 × 10 -11 m 2 s -1 . All three voltammograms were theoretically modeled to reveal surprisingly slow standard electrochemical rate constants, k 0 , of 2.0, 1.5, and 0.19 × 10 -4 cm s -1 respectively for the Ag + |Ag 0 couple. As a potentially faster alternative to the Ag|Ag + system, the voltammetry and kinetics of the TMPD|TMPD + system (where TMPD = N,N,N′,N′-tetramethyl-p- phenylenediamine) was also studied, using neutral TMPD and two TMPD radical cation salts, with BF 4- and NTf 2- counter anions. Diffusion coefficients for TMPD, TMPD + BF 4- , and TMPD + NTf 2- were calculated to be 1.84, 1.35, and 1.43 × 10 -11 m 2 s -1 respectively, and a k 0 value of 2.6-2.8 × 10 -3 cm s -1 was obtained from theoretical fitting of the cyclic voltammetry. This number is an order of magnitude larger than that for the Ag|Ag + system, allowing for the suggestion that the TMPD|TMPD + system may be more suitable than the Ag|Ag + system as a redox couple for use in reference electrodes for ionic liquids. © 2007 American Chemical Society.

Original publication

DOI

10.1021/jp0737754

Type

Journal article

Journal

Journal of Physical Chemistry C

Publication Date

20/09/2007

Volume

111

Pages

13957 - 13966