Semiconducting Bipolar Membranes: Photochemical Salt Pumps

Controlling ion flow with light is important to developing ion-based systems that store and convert light energy for useful purposes such as desalination or signaling. Light-driven ion release from a semiconducting bipolar membrane consisting of a layer of an anionically functionalized polyacetylene (PA(A)) and a cationically functionalized polyacetylene (PA(C)) is demonstrated. The compositional ion asymmetry across the membrane drives photochemical charge separation resulting in oxidation of PA(A) and reduction of PA(C) with the accompanied release of the salt of their counterions. Numerical simulations are also reported supporting the observed phenomenon.