Electrochemical reduction of europium() using tetra--octyl diglycolamide functionalized ordered mesoporous carbon microelectrodes

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2020-05, Vol.8 (2), p.6689-67
• Main Authors: Bertelsen, Erin R, Kovach, Nolan C, Trewyn, Brian G, Antonio, Mark R, Shafer, Jenifer C
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc00824a

This work investigates the one-electron reduction of Eu( iii ) to Eu( ii ) with ordered mesoporous carbon (OMC) in cavity microelectrode (CME) systems. OMC materials with and without tetra- n -octyl diglycolamide (TODGA) functionalization were subjected to voltammetric measurements and compared with commercial carbon black Vulcan® XC-72. The electrochemical reduction of solution Eu( iii ) with unfunctionalized OMC, XC-72, and TODGA-functionalized OMC-both within the electrode matrix and on the electrode surface-is reported. The complexation of Eu( iii ) by TODGA-functionalized OMC prior to electrode preparation incorporates Eu( iii ) as part of the bulk electrode matrix. Under these conditions, the high capacitance obscures the Eu( iii )/Eu( ii ) redox couple. A signal emerges above the background (capacitive) currents when 2-octanol is added to the TODGA-functionalized OMC as a wetting agent. In contrast, surface Eu( iii )-TODGA complexation, when Eu( iii ) contacts the electrode surface exclusively after electrode preparation, provides a strong response. The addition of 2-octanol to TODGA reduces the capacitance of the electrode and narrows the Eu( iii )/Eu( ii ) redox peak widths. The desorption by reductive stripping of Eu( ii ) was demonstrated using a 2-octanol modified TODGA OMC CME, opening the possibility for selective separation of Eu from adjacent trivalent lanthanides. This work investigates the one-electron reduction of Eu( iii ) to Eu( ii ) by ordered mesoporous carbon (OMC), with and without tetra- n -octyl diglycolamide (TODGA) functionalization, in cavity microelectrode (CME) systems.