Light-induced Proton Conductivity in a Photo-acid Doped Polymer
Abstract
Protons are important in natural and artificial light harvesting reactions. Direct conversion of light to proton currents in material platforms has not been adequately explored to date. In conventional semiconductors, light absorption generates mobile electrons and holes, which often increases the conductivity. Here, by analogy we introduce a new idea in which photoacid molecules are embedded in a polymer matrix. Light excitation triggers release of protons from the embedded photoacids resulting in increased protonic conductivity. We used a liquid film of polyethylene glycol doped with a well-known photoacid that is sandwiched between two transparent electrodes. Electrochemical impedance spectroscopy was used to measure the conductivity of the liquid film in the dark and upon shining blue light. It is shown that excitation by light reduces the impedance significantly, especially in the low frequency range. We model the impedance of the system with an equivalent circuit using a diffusive impedance Warburg element. We suggest that the light-induced conductivity change arises mainly from photoreleased protons that manage to escape the zone of influence of the parent ion, approximated here as the Bjerrum length, and avoid recapture.
USC- the AFOSR YIP Award (FA9550-13-1-0128).- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- 2018
- Bibcode:
- 2018APS..MARS43013H