Marta Sevilla1 Antonio Fuertes1

1, Instituto Nacional del Carbón, Oviedo, , Spain

Porous carbon materials are highly demanded for a broad range of applications, such as catalysis/electrocatalysis, adsorption processes or energy storage. Specifically, the field of energy storage and supercapacitors is dramatically increasing and urging to develop porous carbon materials with controlled textural, structural and chemical properties following sustainable, efficient and economic synthesis protocols.
Within this context, my group has developed several synthesis approximations. On one side, the use of biomass or hydrochar, i.e. hydrothermally carbonized biomass, as sustainable platform for the production of advanced porous carbons by means of chemical activation approaches. Hydrochar has several advantages as carbon precursor over biomass, such as a more a more homogeneous structure and an increased degree of aromaticity, which ensures a higher yield of product in the transformation process. By combining hydrochar with a benign substance such as potassium bicarbonate, highly porous carbons with a supercapacitor performance that can compete with that of benchmark KOH-activated carbons can be obtained [1]. However, in certain cases, the soluble and/or melting ability of certain kind of biomasses or biomass derivatives is advantageous. That is the case of using solution synthesis approaches or templating strategies. In this regard, we have recently shown the synthesis of hierarchical porous carbons with a large porosity development from a variety of biomasses or biomass derivatives (e.g. microalgae, soya flour, glucose or glucosamine). By the selection of an appropriate carbon precursor, the porosity can be tailored in the micro-mesopore range [2].
On the other side, the use of organic salts comprising metals with an activating (K, Na) or templating (Ca, Zn or Fe) function, which represents a straightforward, sustainable approximation [3-6]. By their direct thermal treatment at high temperature and the subsequent removal of the inorganic species generated, porous carbons with a variety of pore structures and particle morphology can be obtained. Worth noting is the production of highly porous carbon nanosheets by using potassium citrate [4] or sodium gluconate [5] as precursor. Besides, N-doping of the materials can be accomplished quite easily in-situ or post-synthesis with an N-rich substance. These materials have shown enhanced performance when used in supercapacitors as a result of their special morphology and/or pore structure.

[1] M. Sevilla, A. B. Fuertes, ChemSusChem, 2016, 9, 1880.
[2] M. Sevilla, G. A. Ferrero, A. B. Fuertes, Chem. Mater., 2017, 29, 6900.
[3] M. Sevilla, A. B. Fuertes, J. Mater. Chem. A, 2013, 1, 13738.
[4] M. Sevilla, A. B. Fuertes, ACS Nano, 2014, 8, 5069.
[5] A. B. Fuertes, M. Sevilla, ACS App. Mater. Interfaces, 2015, 7, 4344.
[6] G. A. Ferrero, M. Sevilla, A. B. Fuertes, Carbon, 2015, 88, 239.