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

Abstract

Nitrogen-containing mesoporous carbons with the use of colloidal silica spheres of (14 nm) and chitosan as a carbon precursor were obtained. A removal of such small template particles from carbonized silica-chitosan composite is difficult and HF with a minimum concentration of 15 wt% should be used. By varying the silica-to-chitosan ratio, the porous characteristic of products is controlled. The modification by ZnCl 2 with a molar Zn-to-C (in chitosan mass) ratio of '6' results in the development of microporosity; however it is accompanied by a significant reduction of mesopore volume (V mes ). The addition of ZnCl 2 in a ratio of '5.25' and pH adjustment to 5.8 increase the volumes of micropores, small mesopores, BET surface area to 1975 m 2 /g, and preserve V mes of 4.15 cm 3 /g. The novelty of the presented strategy is the creation of microporosity in the hard-templated materials by incorporating ZnCl 2 into the mixture of Ludox HS-40 template and chitosan precursor, as well as the investigation on how the pH of synthesis influences the final porosity. The pH of a silica-chitosan-zinc solution, equal to 3.9, provides some coordination of Zn 2+ by -OH and -NH 2 groups, whereas pH adjustment to 5.8 results in the precipitation of a new template-Zn(OH) 2 .

An Inter-loop Approach on Hydrothermal Carbonization of Sewage Sludge for the Production of Biochar and Its Application as an Adsorbent for Lead-acid Battery Recycling

“…Therefore, the biochars presented a large heterogeneity of its pore size, drawing attention to further exploring studies on hierarchically structured porous materials (Leżańska et al, 2018). Additionally, as a direct result of the large pore size distribution, the BET method took into account only a small range of mesopores, resulting in the subestimated values of surface speci c area (around 6 m 2 g −1 ), and a discrete pore volume (ranging from 0.02 to 0.05 cm 3 g −1 ) (Table 1).…”

Microporous N-Doped Carbon Obtained from Salt Melt Pyrolysis of Chitosan toward Supercapacitor and Oxygen Reduction Catalysts

“…The ZnCl 2 based melts were also reported to actively drive carbonization of ionic liquids with glucose, polysaccharides, or biomass [ 30 , 31 ] into specific morphology, resulting in high surface area carbons. So far, hierarchical porous carbons have been obtained by the templating approach with silica spheres of a diameter of 14 nm from pure chitosan or a chitosan/ZnCl 2 solution resulting in the creation of microporosity [ 32 ].…”

Laminar N-Doped Carbon Materials from a Biopolymer for Use as a Catalytic Support for Hydrodechlorination Catalysts

“…This method involves the use of corrosive and hazardous solvents to remove the silica templates and generates waste streams that pose a risk, which is a serious drawback. Alternatives have been explored; hence, metallic salts [ 10 , 11 , 12 ], carbonates [ 13 ] and hydroxides [ 14 ] have been postulated as good candidates to develop a well-defined porosity in the carbon matrix, being easily removed with hot water or weakly acidic solutions. The synthesis process uses carbonates, hydroxides, nitrates and chlorates and proceeds through the partial oxidation of the starting carbon, producing CO that contributes to the activation [ 15 ].…”