Design of nitrogen-containing carbonaceous adsorbents for CO2 capture and energy storage applications

The increase of global CO2 concentration, mainly due to anthropogenic emissions from combustion of fossil fuels, is responsible for severe environmental issues, in particular global warming. Limitations in the use of polluting energy sources and the development of strategies for the reduction of CO2 emissions are therefore strictly urgent. Activated carbons can be employed for several applications: separation processes, as catalyst supports as well as electrode/electrolyte components in electrochemical energy storage/conversion devices. Among these, nitrogen-containing ordered mesoporous carbons (NOMCs) are proposed for CO2 up-take. Ordered mesoporous carbons (OMCs) can be synthesized with different pore architectures as nano-replications of a silica hard template, using a three-step procedure: i) infiltration of the carbon source inside the pore channels of silica, ii) pyrolysis of the hybrid system and iii) template removal. For example, this approach has been used to prepare the well-known CMK-type materials: CMK-1, CMK3, CMK-6 and CMK-8 are synthesized using MCM-48, SBA-15, SBA-16 and KIT-6 silica templates, respectively. NOMCs are here proposed as CO2 adsorbents in the context of the carbon capture and storage technologies. In this work, the aforementioned approach, known for the reparation of the so-called CMK-type materials, is exploited for tuning the textural features of the carbonaceous adsorbents and therefore optimizing their capture performances and the kinetics of gas diffusion. Moreover, a nitrogen-containing carbon source was chosen as a precursor, in order to introduce basic sites useful to promote the interaction with the acidic CO2 molecule, fostering in this way also a selective adsorption in a gas mixture. Therefore, the regular, ordered mesoporous architecture and the superficial chemical properties have been investigated in order to study their effect on the CO2 capture performances. The described NOMCs can be applied not only for CO2 up-take, but also in energy storage and conversion devices (lithium or sodium based batteries for instance), photocatalysis or electrocatalytic reduction of CO2. For these applications, they can be used as-synthesized or eventually decorated with specifically selected metal oxides.