(419h) Redox-Active Organometallic Polymers for Environmental and Energy Applications

Authors: 
Su, X., Massachusetts Institute of Technology
Elbert, J., Massachusetts Institute of Technology
Tan, K. J., Massachusetts Institute of Technology
Jamison, T., Massachusetts Institute of Technology
Hatton, T. A., Massachusetts Institute of Technology

Redox metallopolymers have
been explored extensively for catalysis, energy storage and molecular
recognition.1 When properly designed, these charged polymers can
become powerful vehicles to tune the redox-properties at an electrode
interface, due to their fast Faradaic reaction and electron-transfer
properties. Here, we present nanostructured electrodes functionalized with poly(vinyl)ferrocene/carbon nanotubes (PVF-CNT) as a
attractive platform for the selective separation of organic micropollutants
under competitive binding, with separation factors >150 based on specific
functional group recognition for harmful carboxylates, sulfonates
and phosphonates, and ion-capacity >200 mg/g.2
The mechanism for this selectivity is explored through both spectroscopic,
electrochemical and computational methods. In tandem, cobaltocenium-based
polymer counter-electrodes (PMMAECoCp-CNT) were
designed as efficient cathodes to increase pseudocapacitive charge and suppress
side-reactions, especially the water reduction reaction, thus both enhancing
energy storage capabilities (specific capacitance of 498 F/g) as well as
increasing ion-selective behavior of the anode (98% current efficiency towards
ion-selective process). The non-covalent functionalization of these
organometallic polymers onto the electrodes grants cycling stability for over
two days and >5000 cycles. Finally, further cathode design through ligand
exchange has enabled us to develop cation-selective electrodes for both
heavy-metal removal as well as aromatic organic cations – and in tandem,
these asymmetric systems become highly energy-efficient systems for wastewater
treatment, chemical purification and even bio-separations. This work highlights
the potential of asymmetric polymer-functionalized redox-systems for
electrochemical separations and energy storage, and the importance of
organometallic design for selectively targeting molecular-level pollutants.

References

1   G. R. Whittell and I. Manners, Advanced Materials, 2007, 19, 3439-3468.

2 Su, X.; Kulik, H; Jamison, T.F.;
Hatton, T. A. 2016. Anion-selective redox electrodes:
electrochemically-mediated separation with organometallic interfaces. Advanced
Functional Materials.
Advance Article Online. DOI:
10.1002/adfm.201600079