Neutron scattering technique provides new data on adsorption of ions in microporous materials

The adsorption of ions in microporous materials governs the operation of technologies as diverse as water desalination, energy storage, sensing and mechanical actuation.

Until now, however, researchers attempting to improve the performance of these technologies haven't been able to directly and unambiguously identify how factors such as pore size, pore surface chemistry and electrolyte properties affect the concentration of ions in these materials as a function of the applied potential.

To provide the needed information, researchers at the Georgia Institute of Technology and the Oak Ridge National Laboratory have demonstrated that a technique known as small angle neutron scattering (SANS) can be used to study the effects of ions moving into nanoscale pores.

Believed to be the first application of the SANS technique for studying ion surface adsorption in-situ, details of the research were reported recently in the journal Angewandte Chemie International Edition.

Using conductive nanoporous carbon, the researchers conducted proof-of-concept experiments to measure changes in the adsorption of hydrogen ions in pores of different sizes within the same material due to variations in solvent properties and applied electrical potential. Systematic studies performed with such a technique could ultimately help identify the optimal pore size, surface chemistry and electrolyte solvent properties necessary for either maximizing or minimizing the adsorption of ions under varying conditions.

''We need to understand this system better so we can predict the kind of surface chemistry required and the kinds of solvents needed to control the levels of ion penetration and adsorption in pores of different sizes,'' says Gleb Yushin, an associate professor in the Georgia Tech School of Materials Science and Engineering.