title: Evolution of Phosphorus-Containing Groups on Activated Carbons during Heat Treatment.
abstract: Two types of activated carbons have been prepared by H3PO4activation of lignocellulose and by H3PO4modification of activated carbon, and then heat-treated at temperatures from 400 to 900 °C in an atmosphere of N2or H2to investigate the evolution of phosphorus-containing groups. Elemental analysis, X-ray photoelectron spectroscopy,31P nuclear magnetic resonance, nitrogen adsorption, and scanning electron microscopy have been used to analyze the physicochemical properties of the activated carbons. The results show that C-O-P linkages of phosphorus-containing groups can progressively evolve into C-P-O, C3-P═O, C3-P, and eventually elemental phosphorus as a result of heat treatment. Phosphate-like groups are much more thermally stable in an N2than in an H2atmosphere. In N2, C-O-P linkages significantly evolve into C-P-O and C3-P═O at up to 800 °C, whereas C3-P linkages are not formed even at 900 °C. In H2, the corresponding evolution remarkably occurs at 500 °C, forming C3-P linkages and eventually elemental phosphorus. Moreover, the two activated carbons exhibit different evolution trends, suggesting that the evolution happens more easily for phosphorus-containing groups located on the edges of graphite-like crystallites than those in the lattice. Finally, we propose different evolution pathways of phosphorus-containing groups upon heat treatment in N2and H2atmospheres.
authors.affiliation: College of Chemical Engineering, Jiangsu Key Laboratory of Biomass-Based Green Fuels and Chemicals, Nanjing Forestry University , Nanjing 210037, China.
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Chemical Engineering, Jiangsu Key Laboratory of Biomass-Based Green Fuels and Chemicals, Nanjing Forestry University , Nanjing 210037, China.
authors.forename: Songlin
authors.identifier: 0000-0002-9760-2918
authors.initials: S
authors.lastname: Zuo
authors.affiliation: College of Materials Science and Engineering, Hunan University , Changsha 410082, China.
authors.forename: Jianxiao
authors.initials: J
authors.lastname: Yang
authors.affiliation: Institute for Materials Chemistry and Engineering Sciences, Kyushu University , Fukuoka 8168580, Japan.
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Yoon