Nafion-Coating of the Electrodes Improves the Flow-Stability of the Ag/SiO₂/Ag₂O Electroosmotic Pump

다국어 초록 (Multilingual Abstract)

<P>When a current or a voltage is applied across the ceramic membrane of the nongassing Ag/Ag<SUB>2</SUB>O-SiO<SUB>2</SUB>-Ag/Ag<SUB>2</SUB>O pump, protons produced in the anodic reaction 2Ag(s) + H<SUB>2</SUB>O → Ag<SUB>2</SUB>O(s) + 2H<SUP>+</SUP> + 2e<SUP>–</SUP> are driven to the cathode, where they are consumed by the reaction Ag<SUB>2</SUB>O(s) + H<SUB>2</SUB>O + 2e<SUP>–</SUP> → 2Ag(s) + 2 OH<SUP>–</SUP>. The flow of water is induced by momentum transfer from the electric field-driven proton-sheet at the surface of the ceramic membrane. About 10<SUP>4</SUP> water molecules flowed per reacted electron. Because dissolved ions decrease the field at the membrane surface, the flow decreases upon increasing the ionic strength. For this reason Ag<SUP>+</SUP> ions introduced through the anodic reaction and by dissolution of Ag<SUB>2</SUB>O decrease the flow. Their accumulation is reduced by applying Nafion-films to the electrodes. The 20 μL min<SUP>–1</SUP> flow rate of 6 mm i.d. pumps with Nafion coated electrodes operate daily for 5 min at 1 V for 1 month, for 70 h when the pump is pulsed for 30 s every 30 min, and for 2 h when operating continuously.</P><P><B>Graphic Abstract</B>
<IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2011/ancham.2011.83.issue-12/ac201118t/production/images/medium/ac-2011-01118t_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac201118t'>ACS Electronic Supporting Info</A></P>