Doctoral thesis helps better understand and predict carbon nanostructure and capacitance relationships in energy storage devices

Doctoral thesis by M.Käärik with some tools. Photo: University of Tartu

In a doctoral dissertation defended in the Institute of Chemistry of the University of Tartu, experimental and cheminformatics methods were used to study methods for producing nanoporous carbon materials and their capacitance characteristics. For the first time, the authors were able to predict an application-relevant property of heterostructural carbon by using experiment-derived structure descriptors.

Increasingly topical environmental issues force us to pay more attention to alternative energy storage devices and the green materials used in them. Such materials also include nanoporous carbon. In addition to its ability to store electrical energy, nanoporous carbon has a great potential to be used as molecular sieves for the purification and adsorption of gases and liquids, in the selective separation of ions, and as a catalyst support in low-temperature fuel-cells.

“All these applications require the optimal specific nanostructure for the carbon material, so it is crucial to be able to purposefully influence the formation and porosity of nanostructures in carbon synthesis,” said Maike Käärik, Research Fellow at the Institute of Chemistry of the University of Tartu, and author of the doctoral thesis.

The prevailing topic in the dissertation is finding relationships between the electrical double-layer capacitance of carbide-derived carbon (CDC) and the experiment-derived structure descriptors, using the quantitative nano-structure-property relationship (QnSPR) approach. More than 200 different micro- and macrostructured carbon materials were synthesised, and all data were pooled into a unique database of nanoporous carbons. The doctoral thesis thoroughly analyses the relationships between the synthesis conditions and the porous structure of carbon, and gives a comprehensive overview of effect of pore size distribution, measured by gas adsorption analysis, on the electrical double-layer capacitance of carbon.

“The results of this research help to gain a broader understanding of the role of ultra-small pores in achieving high capacitance in energy storage devices,” explained the supervisor Jaan Leis, Senior Research Fellow at the Institute of Chemistry of the University of Tartu.

As a result of the research, it was possible for the first time to construct multiparametric regression models for describing and predicting the electrical capacitance of porous carbon, using experiment-derived structure descriptors. “The importance of this work consists primarily in the fact that a mathematical model was found, which enables predicting the properties of carbon materials with difficult-to-describe structures,” Maike Käärik said.

“Attempts to describe and predict the quantitative structure-property relationships of nanomaterials have been made over the last decades. The problem has been the lack of datasets of nanomaterials suitable for modelling, and the calculating or measuring of appropriate parameters describing the molecular structure. Maike Käärik in her dissertation has overcome both obstacles and achieved an excellent modelling result,” added Uko Maran, co-supervisor of the thesis, Senior Research Fellow at the Institute of Chemistry of the University of Tartu.

Further information: Maike Käärik, Research Fellow in Molecular Technology, Institute of Chemistry, University of Tartu, +372 737 5279, maike.kaarik [ät]