A combined salt–hard templating approach for synthesis of multi-modal porous carbons used for probing the simultaneous effects of porosity and electrode engineering on EDLC performance

Abstract

A B S T R A C TA new approach, based on a combination of salt and hard templating for producing multimodal porous carbons is demonstrated. The hard template, silica nanoparticles, generate mesopores ($22 nm), and in some cases borderline-macropores ($64 nm), resulting in high pore volume ($3.9 cm 3 /g) while the salt template, zinc chloride, generates borderline-mesopores ($2 nm), thus imparting high surface area ($2100 m 2 /g). The versatility of the proposed synthesis technique is demonstrated using: (i) dual salt templates with hard template resulting in magnetic, nanostructured-clay embedded ($27% clay content), high surface area ($1527 m 2 /g) bimodal carbons ($2 and 70 nm pores), (ii) multiple hard templates with salt template resulting in tri-modal carbons ($2, 12 and 28 nm pores), (iii) low temperature (450°C) synthesis of bimodal carbons afforded by the presence of hygroscopic salt template, (iv) easy coupling with physical activation approaches. A selected set of thus synthesized carbons were used to evaluate, for the first time, the simultaneous effects of carbon porosity and pressure applied during electrode fabrication on EDLC performance. Electrode pressing was found to be more favorable for carbons containing hard-templated mesopores ($87% capacitance retention at current density of 40 A/g) as compared to those without ($54% capacitance retention).

Ordered Mesoporous Carbons Loading on Graphene after Different Molten Salt Activations for Supercapacitor Applications

“…This novel salt melt synthesis (SMS) method possesses many advantages, for example, molten salt has wide operational temperature range and is excellent solvents at high temperature, the salts can easily be isolated from the product, and more importantly, the porogen is environmental friendly and can be recycled . Multimodal porous carbons produced by a combination of salt and hard template, could show an extremely high surface area (2100 m 2 g −1 ) and specific capacitance (190 F g −1 at 0.5 A g −1 ) . Another report is that porous carbons are produced by the precursors (the common carbohydrate glucose, ionic liquids etc.)…”

Hierarchical porous carbon templated with silica spheres of a diameter of 14 nm from pure chitosan or a chitosan/ZnCl2 solution

“…In such a mesoporous system, micropores may be produced, by known activators, such as ZnCl 2 [18] or, for example, TEOS [19], added directly to the mixture during synthesis. It is possible to modify the hard precursor by means of physical activators (e.g.…”

“…Mainly micropores and small mesopores are generated after washing of salt particles. The presence of ZnCl 2 ensures a higher degree of carbonization of the glucose-silica composite [18]. An interesting synthesis approach, which consisted of hard templating with colloidal silicas and salt-templating by ZnCl 2 and glucose as a carbon precursor, in some cases completed by physical activation with CO 2 , resulted in the trimodal porous carbon.…”

“…The pores of a diameter of ca. 2, 12 and 28 nm were generated in a single material [18]. The physical activation with CO 2 , resulted in a substantial increase of microporosity and as a result BET surface area up to ca.…”

“…The high capacitance retention at a very high current density of 40 A/g, of ca. 87% was obtained when 'hard-templated' mesopores were presented in carbon materials [18].…”