For over half a century, it has been recognized that the classical physics that dictates the behavior of hydrated ion-exchange membranes, such as Nafion, and semiconductors, such as doped silicon, are similar. However, no demonstrations of photovoltaic action from ion-exchange materials existed. We recently reported a synthetic light-driven proton pump derived from an ion-exchange membrane. Absorption of light by covalently bound photoacid molecules resulted in photovoltaic action. This design lacked a second permselective membrane contact, which limited its performance. Here, we report a ∼60-fold increase in the photovoltage through use of a bipolar membrane structure consisting of a cation-exchange membrane affixed to an anion-exchange membrane. The junction between the layers was characterized in detail using electrochemistry, scanning electron microscopy, spectroscopy, and thermal gravimetric analysis. Our results represent considerable progress toward a device that directly converts sunlight into ionic electricity, which has implications for direct solar desalination of salt water.

半个多世纪以来，人们已经认识到决定水合离子交换膜（如Nafion）和半导体（如掺杂硅）行为的经典物理学是相似的。但是，没有离子交换材料产生光伏作用的证明。我们最近报道了一种源自离子交换膜的合成光驱动质子泵。共价键合的光酸分子对光的吸收导致光伏作用。该设计缺少第二个选择性渗透膜接触，这限制了它的性能。在这里，我们报道了通过使用双极性膜结构将光电压增加约60倍，该结构由固定在阴离子交换膜上的阳离子交换膜组成。层之间的接合点使用电化学进行了详细描述，扫描电子显微镜，光谱学和热重分析。我们的结果表明，在将太阳光直接转换为离子电的设备方面取得了长足的进步，这对盐水的直接太阳能淡化具有重要意义。