Effect of surface phosphorus functionalities of activated carbons containing oxygen and nitrogen on electrochemical capacitance

Abstract

Micro/mesoporous activated carbons containing oxygen and phosphorus heteroatoms were modified by incorporation of nitrogen using melamine and urea precursors. The surface chemistry was analyzed by the means of elemental analysis, XPS, and 31P MAS NMR. The results indicate that upon the incorporation of nitrogen at high temperatures not only new species involving carbon/nitrogen/oxygen are formed but also the phosphorous environment is significantly altered. Both urea and melamine precursors have similar effects on formation of P–N and P–C bonds. These compounds, although present in small but measurable quantities seem to affect the performance of carbons in electrochemical capacitors. With an increase in the heterogeneity of phosphorus containing species and with a decrease in the content pyrophosphates the capacitance increases and the retention ratio of the capacitor is improved.

Easy approach to synthesize N/P/K co-doped porous carbon microfibers from cane molasses as a high performance supercapacitor electrode material

“…The contribution of metallic K is also revealed in the K 2p 3/2 and K 2p 1/2 small peaks at 294.5 and 297.2 eV. The broad O 1s peaks can be deconvoluted into three surface groups namely O-I (530.8 eV), O-II (532.6 eV) and O-III (535.2 eV), which represents oxygen double bonded to carbon (C]O) or nonbridging oxygen bonded to phosphorus (P]O), singly bonded oxygen (-O-) in alcohol (C-OH) or ether (C-O-C), also includes bridging oxygen in the phosphate group (C-O-P) and chemisorbed oxygen (carboxylic groups) and water, 36,40 respectively. The surface oxygen content gradually decreased with carbonization temperature increasing from 773.15 to 1173.15 K due to deoxygenation phenomena and further aromatization of the graphitic framework.…”

“…The existence of nitrogen containing surface groups N-Q and N-X contributes positively on the electron transfer through the carbon electrodes and hence improves the electrochemical performance at fast chargedischarge rates. 36 There is an apparent redox hump in the CV curves of CMFs supercapacitors in the voltage range of 0-1.5 V, conrming the occurrence of pseudocapacitance associated with plentiful nitrogen and oxygen containing surface groups which are stable and electrochemically active such as N-6, N-Q, N-X and O-II groups. Also, one can show that the electrochemical performance in TEABF 4 /ACN electrolyte is superior to those in EMIDCA/ACN and EMIBF 4 /ACN electrolytes (Fig.…”

“…The binding energy around 133.0 eV also covers the contribution from nonbridging (P]O) and bridging oxygen bonded to phosphorus (C-O-P) as well as phosphonate structures (C-PO 3 , C 2 -PO 2 or C 3 -P). 36,40 Another surface phosphorus group at the binding energy of 136.1 eV was observed for CMF-1173.15, which can be attributed to phosphorus oxide (P 2 O 5 ). 40 Total phosphorus content on the surface shows an increase up to 1073.15 K and then decreases with further increase in the carbonization temperature.…”

“…Puziy et al 40 and Wang et al 41 have reported similar trend in their work. Hulicova-Jurcakova et al 36 have shown that P-doping could increase the voltage window tolerated by the electrode material at positive potentials due to the blockage of active oxidation sites by phosphate groups. The K 2p spectrum comprises two asymmetric peaks at the binding Table 3 Relative and weighted surface concentrations of nitrogen and oxygen species obtained by fitting the N 1s and O 1s core level peaks of XPS spectra…”

Dual-heteroatom-modified ordered mesoporous carbon: Hydrothermal functionalization, structure, and its electrochemical performance

“…4 Great effort has been paid to develop heteroatom (such as B, N, O, P, S) incorporated OMCs as advanced electrode materials in electrochemical energy storage and as an alternative to current catalysts for biomass conversion. For instance, both the nitrogen-doped ordered mesoporous graphitic arrays 5 and metal-free nitrogen-containing nanocarbon 6 can cause electron modulation to provide desirable electronic structures with relatively good electro-catalytic activity and long-term stability toward the oxygen reduction reaction for fuel cells; the B-, 7-10 O-, 11-13 N-, 9,11,12,14 and Pincorporated 8,12,15 OMCs exhibited superior electrochemical performances to their non-incorporated counterparts when used as supercapacitor electrodes; heteroatoms (such as B, N, P, S) increase the activity and/or selectivity in triglyceride transesterification, 16 oxidative dehydrogenation and alkane activation reactions 17 on nanocarbon and OMCs; N-doped OMC with a graphitic wall structure was a good metal-free basic catalyst 18 and catalyst support. 19 Recently, the phosphorus-doped porous carbon nitride was reported to present not only a much better electrical conductivity but also an improvement in photocurrent generation, 20 which is interesting for polymeric batteries.…”