Single-layer MoS2 nanopores as nanopower generators

Blue energy is a desirable renewable resource, involving the osmotic transport of ions through a membrane from seawater to fresh water; here, nanopores have been created in two-dimensional molybdenum-disulfide membranes, and shown to generate a substantial osmotic power output. Osmotic power generation is a promising renewable energy source. This study demonstrates the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanogenerators. The transport of water through a membrane scales inversely with membrane thickness, so atomically thin materials should provide the ideal medium to host the nanopores in an osmotic power generator. Aleksandra Radenovic and colleagues produced nanopores in two-dimensional MoS2 and, using a salt gradient across a single nanopore, generated a power output per area orders of magnitude greater than that previously reported for nanotubes. They also show that a chemical potential gradient across a single nanopore in MoS2 can generate enough power to operate a single-layer MoS2 transistor. Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as ‘blue energy’1,2,3. Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient4 or by an osmotic potential resulting from a salt concentration gradient5. For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness5,6,7. Here we demonstrate the use of single-layer molybdenum disulfide (MoS2) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 106 watts per square metre—a current that can be attributed mainly to the atomically thin membrane of MoS2. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment8,9,10,11—for example, a piezoelectric zinc oxide nanowire array8 or single-layer MoS2 (ref. 12). We use our MoS2 nanopore generator to power a MoS2 transistor, thus demonstrating a self-powered nanosystem.