XPS and NMR studies of phosphoric acid activated carbons

Chemical structure of phosphorus species in two series of polymer-based and fruit-stone-based carbons obtained by phosphoric acid activation at 400–1000 °C were investigated by XPS and solid state 31P-NMR and 13C-NMR. It has been shown that the most abundant and thus thermally stable phosphorus species in all investigated carbons is phosphate-like structure bound to carbon lattice via C-O-P bonding. Small contribution of phosphonates (C-P-O linkage) was observed by 31P NMR in carbons obtained at temperature range of 500–700 °C, phosphorus oxide was evidenced by XPS in carbon prepared at 900 °C and elemental phosphorus in carbon activated at 1000 °C.