Bacterial-Cellulose-Derived Carbonaceous Electrode Materials for Water Desalination Via Capacitive Method: the Crucial Role of Defect Sites

Abstract

Electrosorptive desalination is a very simple and appealing approach to satisfy the increasing demand for drinking water. The large-scale application of this technology calls for the development of easy-to-produce, cheap and highly performing electrode materials and for the identification and tailoring of their most influential properties, as well. Here, biosynthesised bacterial cellulose is used as a carbon precursor for the production of three-dimensional nanostructures endowed with hierarchically porous architecture and different density and type of intrinsic and hetero-atom induced lattice defects. The produced materials exhibit unprecedented desalination capacities for carbon-based electrodes. At an initial concentration of 585 mg L-1 (10 mmol L-1), they are able to remove from 55 to 79 mg g(-1) of salt; as the initial concentration rises to 11.7 g L-1 (200 mmol L-1), their salt adsorption capacity reaches values ranging between 1.03 and 1.35 g g(-1). The results of the thorough material characterisation by complementary techniques evidence that the relative amount of oxygenated surface functional species enhancing the electrode wettability play a crucial role at lower NaCl concentrations, whereas the availability of active non-sp(2) defect sites for adsorption is mainly influential at higher salt concentrations.