Researchers have discovered that optimised nanoporous carbons can improve the performance of energy storage and conversion devices.
A research team from the Helmholtz-Zentrum Berlin (HZB) Institute for Soft Matter and Functional Materials collaborated with researchers from the University of Tartu, Estonia, to inquire the nanoarchitecture, inner surface, size, form, and distribution of nanopores in dependence of the synthesis conditions.
The collective from Estonia produced a series of nanoporous carbons by reacting a powder of molybdenum carbide (Mo2C) with gaseous chlorine at 600, 700, 800, 900, and 1000 degrees Celsius. Depending on the synthesis conditions chosen, the nanoporous carbon exhibit different properties such as surface area, porosity, electronic and ionic conductivity, hydrophilicity, and electrocatalytic activity.
The team analysed the surface structure using transmission electron microscopy. The interior surface area of nanocarbon materials is often investigated by adsorption of gas, however, this method is comparatively inaccurate. For deeper insights, Dr Eneli Härk and her colleagues at HZB worked with small-angle X-ray scattering, a technique permitting to obtain information on various structural features on the nanometre scale including the mean pore size.
The benefits of small-angle X-ray scattering
Small-angle X-ray scattering not only provides information on the precise inner surface area and the average pore size, but also on their angularity, i.e., sharp edges of formed pores, which play a major role for the functionalisation of the materials.
“The SAXS analysis summarises over an enormous amount of micropores omitting misleading assumptions thereby directly relating the nanostructural architecture of the material to macroscopic technical parameters under investigation in engineering” Härk explains.
The main aim was to understand structural formation, and electrochemical characteristics of carbon as a function of the synthesis temperature. “For optimal function, not only the high inner surface area is crucial, but the pores should have exactly the right shape, size and distribution”, says Härk.