New Insights into the Structure of Nanoporous Carbons from NMR, Raman, and Pair Distribution Function Analysis

Alexander C Forse (1) , Céline Merlet (1) , Phoebe K Allan (1) , Elizabeth K Humphreys (1) , John M Griffin (1) , Mesut Aslan (2) , Marco Zeiger (2) , Volker Presser (2) , Yury Gogotsi (3) , Clare Grey (1)

1 CAM - University of Cambridge [UK]
2 INM - Leibniz Institute for New Materials
3 A. J. Drexel Nanomaterials Institute and Materials Science and Engineering Department

The structural characterization of nanoporous carbons is a challenging task as they generally lack long-range order and can exhibit diverse local structures. Such characterization represents an important step toward understanding and improving the properties and functionality of porous carbons, yet few experimental techniques have been developed for this purpose. Here we demonstrate the application of nuclear magnetic resonance (NMR) spectroscopy and pair distribution function (PDF) analysis as new tools to probe the local structures of porous carbons, alongside more conventional Raman spec-troscopy. Together, the PDFs and the Raman spectra allow the local chemical bonding to be probed, with the bonding becoming more ordered for carbide-derived carbons (CDCs) synthesized at higher temperatures. The ring currents induced in the NMR experiment (and thus the observed NMR chemical shifts for adsorbed species) are strongly dependent on the size of the aromatic carbon domains. We exploit this property and use computer simulations to show that the carbon domain size increases with the temperature used in the carbon synthesis. The techniques developed here are applicable to a wide range of porous carbons and offer new insights into the structures of CDCs (conventional and vacuum-annealed) and coconut shell-derived activated carbons.

Domaines: Matériaux; Chimie théorique et/ou physique

Alexander C Forse, Céline Merlet, Phoebe K Allan, Elizabeth K Humphreys, John M Griffin, et al.. New Insights into the Structure of Nanoporous Carbons from NMR, Raman, and Pair Distribution Function Analysis. Chemistry of Materials, 2015, 27 (19), pp.6848-6857. ⟨10.1021/acs.chemmater.5b03216⟩. ⟨hal-01985735⟩