Composite laminar membranes for electricity generation from water evaporation

Harvesting clean energy from water evaporation has been extensively investigated due to its sustainability. To achieve high efficiency, energy conversion materials should contain multiple features which are difficult to be simultaneously obtained from single-component materials. Here we use composite laminar membranes assembled by nanosheets of graphene oxide and mica, and find a sustained power density induced by water evaporation that is two orders of magnitude larger than that from membranes made by either of the components. The power output is attributed to selective proton transport driven by water evaporation through the interlayer nanochannels in the membranes. This process relies on the synergistic effects from negatively charged and hydrophilic mica surfaces that are important for proton selectivity and water transport, and the tunable electrical conductivity of graphene oxide that provides optimized internal resistance. The demonstrated composite membranes offer a strategy of enhancing power generation by combining the advantages from each of their components.