Nanofluidic homogeneous membranes with light-driven active ion transport properties for blue energy harvesting

Salinity gradient energy harvesting is still limited to rather small working areas in laboratories. Here, we report a thylakoid-inspired nanofluidic system based on a two-dimensional homogeneous multilayer membrane for salinity gradient energy harvesting, assisted by a light-driven active ion transport. The membrane is assembled by graphene oxide (GO) nanosheets decorated with photoelectric 5,10,15,20-tetrakis(4-aminophenyl) porphyrin molecules, denoted as TGO. Upon light illumination on the low concentration side, a photovoltaic gradient is established via light-induced charge separation to drive active cation transport from the unilluminated side to the illuminated side through interlayer spacing. Combining with the self-diffusive cation transport, the TGO membrane shows an enhanced output power density of 1.17 W m−2 with a working area of 0.2 mm2 under 50-fold concentration gradient, an ∼54% increase from the original. Furthermore, the applications in different electrolyte solutions with mono- or multications confirm the feasibility of photoenhanced salinity gradient energy harvesting, with a 43% increase in the combination of artificial seawater/river water.