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Keywords:

  • aerogels;
  • carbon monolith;
  • hydrothermal carbonization;
  • sustainability;
  • green chemistry

Abstract

Hierarchically structured carbon aerogels are produced in a simple, rapid, efficient, and sustainable hydrothermal approach, using only glucose as the carbon precursor. Using sodium borate (borax) as a novel complex structure directing agent nanostructured, carbon monoliths, structurally similar to the well-known sol-gel monoliths made of silica are obtained. Experimental results indicate the acetalization reaction of monosaccharides with their dehydration product hydroxymethylfurfural to be very important and inhibiting in the process of hydrothermal carbonization. Addition of borax, leads to a competitive complexation of diols, resulting in promising secondary catalytic effect with regard to carbon yield. Accordingly, it is shown that the sugar:borax ratio directs the primary carbon nanoparticle size into the sub −50 nm range, while their spinodal destabilization ultimately results in the controlled aggregation of carbonaceous particles leading to the formation of monoliths in a simple one step hydrothermal process. Post-synthesis thermal carbonization is also used to increase surface area to the medium-high range, introducing electric conductivity into the carbon monoliths. The resulting materials are promising candidates for applications in flash chromatography, for fast adsorption/purifications, and as porous conductive electrodes.