On the use of carbon black loaded nitrogen-doped carbon aerogel for the electrosorption of sodium chloride from saline water

Abstract

Highly micro-mesoporous carbon electrodes have been synthesized by the polycondensation of resorcinol-formaldehyde-melamine mixtures in the presence of a carbon conductive additive.The materials showed high surface functionalization (N-and O-groups) provided by the precursors. Despite the low amount used, the conductive additive had a marked effect on the porosity of the aerogels; for a given series, the carbon black loaded materials showed similar micropore volumes and a more developed mesoporosity than the pristine aerogels. Furthermore, the activation treatment under CO 2 atmosphere led to an increase in the surface area along with a widening of the mesoporosity. The synthesized aerogels were explored as electrodes for the electro-assisted removal of sodium chloride from saline water. A desalting capacity of 7.3 mg/g was obtained for monolith electrodes of sample MRF-Act/CB, along with an excellent chemical stability upon charge and discharge at high polarization voltages. Such good electrochemical performance is due to the combination of an adequate pore network and surface functionalization with an enhanced electrical conductivity achieved upon the incorporation of the carbon black additive during the polycondensation of the aerogel precursors.

Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

“…In a previous study we reported the two-step synthesis of N-doped carbon aerogels based on the prepolymerization of melamine-resorcinol-formaldehyde (MRF) mixtures [26,27]. Regardless of the solution pH and M/R molar ratio, the hydrogels prepared by the conventional one-step route displayed essentially a microporous character, as opposed to the meso-/macroporous network of those prepared upon the prepolymerization of the precursors.…”

“…Organic hydrogels are mechanically reinforced upon carbonization at high temperature to render denser carbon gels, that become more rigid (although typical Young modules are still a factor of 100–1000 lower than those of silica glass) but their deformation capacity decreases [9,20,24]. In a previous study we reported the good electrochemical performance of binderless monolithic aerogel electrodes over powdered materials due to the combination of a nanoporous structure interconnected with a macroporous network [26,27,28]; their technological implementation at large scale was, however, limited due to the large shrinkage and deformation of the pieces after the carbonization; the contact between the bent monolithic electrodes and the current collector was compromised, leading to important efficiency losses due to resistance.…”

Titanium Dioxide Nanotubes as Model Systems for Electrosorption Studies

“…Previous literature on electrosorption mainly focused on electrode development, and was mostly for specific applications [ 13 , 14 , 15 ]. Porous carbons are often the choice of materials for electrosorption as they combine a high surface area and good electrical conductivity [ 16 , 17 ].…”

On the use of diatomite as antishrinkage additive in the preparation of monolithic carbon aerogels

“…As for the conductivity, it is mainly controlled by the presence of the carbon black (i.e., 2.1 and 7.7 mS/cm for C-MRF1 and C-MRF1-B; 1.0 and 3.9 mS/cm for C-RF1 and C-RF1-B; 2.2 and 4.3 mS/cm for C-MRF2-D and C-MRF1-BD, respectively); 5 after etching off the diatomite (insulator) the electrodes present conductivity values closed to those prepared without the siliceous additive, although differences also depend on the formulations (ca. N-doped aerogels display higher conductivity than RF ones) [4,5]. In summary, we have fabricated monolithic carbon aerogels with improved mechanical properties while maintaining outstanding porous features and improved electrical conductivity provided by the carbon black additive [4].…”

“…The usually fragile hydrogels are mechanically reinforced upon carbonization as they become more rigid with increased Young modules [2,3], but their deformation capacity decreases. In previous works we have reported the preparation of carbon aerogels using various precursors with enhanced conductivity and chemical resiliency to oxidation [4,5]. Despite the good electrochemical performance, the use of monolithic electrodes was limited due to the large shrinkage and deformation of the pieces after carbonization -leading to densification of the matrix-[5]; this is a challenge for electrochemical applications where the contact between the electrode material and the current collector is crucial to avoid efficiency losses due to resistance.…”