| Autor: |
Yan Z; Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA., Hitt JL; Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA., Zeng Z; Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA., Hickner MA; Department of Materials Science and Engineering, Department of Chemistry, Pennsylvania State University, Philadelphia, PA, USA., Mallouk TE; Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA. tem5@psu.edu. |
| Abstrakt: |
The efficient conversion of electricity to chemicals is needed to mitigate the intermittency of renewable energy sources. Driving these electrochemical conversions at useful rates requires not only fast electrode kinetics, but also rapid mass and ion transport. However, little is known about the effect of local environments on ionic flows in solid polymer electrolytes. Here, we show that it is possible to measure and manipulate the local pH in membrane electrolysers with a resolution of tens of nanometres. In bipolar-membrane-based gas-fed CO 2 electrolysers, the acidic environment of the cation exchange layer results in low CO 2 reduction efficiency. By using ratiometric indicators and layer-by-layer polyelectrolyte assembly, the local pH was measured and controlled within an ~50-nm-thick weak-acid layer. The weak-acid layer suppressed the competing hydrogen evolution reaction without affecting CO 2 reduction. This method of probing and controlling the local membrane environment may be useful in devices such as electrolysers, fuel cells and flow batteries, as well as in operando studies of ion distributions within polymer electrolytes. |
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