Ultrashort nanopores of large radius can generate anomalously high salinity gradient power

Using ultrashort nanopores in salinity gradient power seems promising, however, their poor ion selec-tivity is disadvantageous. We show that this difficulty can be circumvented by adopting a two-dimensional material having a high surface charge density. Through raising the surface charge density, both the electric power and the transference number can both be enhanced effectively. For example, for a cylindrical nanopore having length 2 nm, radius 2 nm and surface charge density-1000 mC/m(2), the transference number can approach ca. 0.97 and the electric power ca. 200 pW if the salt concentration ratio across the nanopore is (1000/1), much higher than previous reported values of 3.13 pW in similar systems having longer pores (-1000 nm) and lower surface charge density (-60 mC/m(2)). The underlying mechanisms of the present novel salinity gradient power system are investigated in detail for the first time. In particular, the profiles for the concentration of ions and its flux inside the nanopore are examined to explain the ion transport phenomena observed. Anomalously, if the surface charge density is sufficiently high (e.g.,-1000 mC/m(2)), a nanopore of radius as large as 50 nm can still generate appreciable electric power (ca. 45 pW). (C) 2020 Elsevier Ltd. All rights reserved.