Carbon foams from sucrose employing different metallic nitrates as blowing agents: Application in CO2 capture

Abstract

Carbon foams were prepared employing sucrose as the carbon source. The porosity of the materials as well as the morphology was controlled using different metallic nitrates during the synthesis, such as aluminum (obtaining EsAl foam), iron (obtaining EsFe foam) and silver (obtaining EsAg foam) nitrate. The samples have interconnecting pores with a turbostratic structure, where the EsFe foam shows a more ordered structure. The addition of the chemical agents promotes improvements in the porosity of the foams, highlighting those obtained with the aluminum nitrate nonahydrate - EsAl (98%) and iron nitrate nonahydrate - EsFe (90%), as well as a greater control of pore growth avoiding collapse. All carbon foams presented a microporous nature, but EsFe foam also present mesoporosity (with pore sizes between 2.2 to 3.5 nm). The high specific surface area values for EsAl and EsFe carbons (600 and 380 m2/g) were attributed to in situ activation during carbonization of the foams. All carbon foams present ultramicropores with pore sizes less than 0.6 nm. The synthesized carbon foams have interesting CO2 adsorption capacities, mainly the EsAl foam that reach CO2 adsorption capacities (at 1000 kPa) of 4 and 4.4 mmol/g at 50 °C and at 35 °C, respectively. These capacities of the carbon foams obtained were similar to those reported in the bibliography for other carbon materials, shows their great potential as CO2 adsorbents. The isosteric heat of CO2 adsorption show that the CO2 capture with the carbon foams synthesized is associated with a physisorption process.