Monograin Membranes for Biomimetic Solar Water Splitting : Stepwise Opening of Ionically Conductive Channels

In order to mimic the Thylakoid membrane for artificial photosynthesis with its photosynthetic reaction centers in parallel to proton transporting ATP synthase units, new composite membranes were designed and characterized. Polyurethane and water based Aquivion® PFSA solutions were mixed to prepare composite membranes which allow in its polyurethane part the fixation of semiconductor single crystalline grains, while the Aquivion® PFSA component allows the formation of ionically conductive pathways through the membranes. The formation of ionically conductive parts in the membrane can be activated by swelling or electrochemical drag of water into the membrane. The latter happens by current flux between electrodes on both sides of the membrane. The current here increases stepwise due to sequential opening of new conductive channels. For membranes with embedded semiconductor grains the ionic conductivity is much larger since here the hydrophilic parts of the composite polymer orient towards the semiconductor surface leading to oriented conductive channels.