“…The NO profiles started at ∼950 K and reached a maximum at ∼1200 K. HCN and C 2 N 2 were not detected during TPD suggesting that −CN species are not present in the partially gasified samples. These results are consistent with the desorption of char nitrogen in carbons partially gasified in oxygen mainly as NO resulting from the decomposition and reaction of carbon nitrogen and carbon oxygen surface species. ,, 10 Temperature-programmed desorption profiles for A-N-B51.8 and CB873-B74.5.…”
Section: Resultssupporting
confidence: 71%
“…The gas evolution profiles were monitored for the following mass/charge ( m / z ) values, 14, 18, 27, 28, 30, and 44, which correspond to N 2 2+ , H 2 O, HCN, CO, NO, and CO 2 . A more detailed description of the TG−MS and the procedure used is given elsewhere …”
X-ray absorption near edge structure (XANES) was used to investigate the fate of nitrogen functional groups in carbons derived from acridine, carbazole, and polyacrylonitrile during carbonization. Acenaphthylene and poly(vinyldene chloride) carbons with nitrogen incorporation by ammonia treatment at elevated temperatures were also studied. In general, the nitrogen XANES data provided more detail than the corresponding X-ray photoelectron spectroscopy (XPS) results and confirm the overall picture obtained from XPS involving the greater stability of pyridinic and quaternary nitrogen functionalities with increasing severity of pyrolysis. Partial gasification of the carbons in 20% oxygen/argon produced a new peak or greatly increased the intensity of an existing nitrogen XANES peak at ∼401.5 eV which was independent of the nitrogen functionality originally present in the carbon. The oxygen XANES spectra showed that carbonyl and carboxylic acid/acid anhydride functionality were also present on the surface of carbons partially gasified with oxygen. The XANES studies have also been compared with the temperatureprogrammed combustion and temperature programmed desorption studies of the carbons. The results are consistent with the presence of pyridone functionality in the partially gasified carbons. The overlap of bands may obscure the interpretation of data from X-ray absorption spectroscopy, and information is required from a number of techniques in order to provide a more detailed view.
“…The NO profiles started at ∼950 K and reached a maximum at ∼1200 K. HCN and C 2 N 2 were not detected during TPD suggesting that −CN species are not present in the partially gasified samples. These results are consistent with the desorption of char nitrogen in carbons partially gasified in oxygen mainly as NO resulting from the decomposition and reaction of carbon nitrogen and carbon oxygen surface species. ,, 10 Temperature-programmed desorption profiles for A-N-B51.8 and CB873-B74.5.…”
Section: Resultssupporting
confidence: 71%
“…The gas evolution profiles were monitored for the following mass/charge ( m / z ) values, 14, 18, 27, 28, 30, and 44, which correspond to N 2 2+ , H 2 O, HCN, CO, NO, and CO 2 . A more detailed description of the TG−MS and the procedure used is given elsewhere …”
X-ray absorption near edge structure (XANES) was used to investigate the fate of nitrogen functional groups in carbons derived from acridine, carbazole, and polyacrylonitrile during carbonization. Acenaphthylene and poly(vinyldene chloride) carbons with nitrogen incorporation by ammonia treatment at elevated temperatures were also studied. In general, the nitrogen XANES data provided more detail than the corresponding X-ray photoelectron spectroscopy (XPS) results and confirm the overall picture obtained from XPS involving the greater stability of pyridinic and quaternary nitrogen functionalities with increasing severity of pyrolysis. Partial gasification of the carbons in 20% oxygen/argon produced a new peak or greatly increased the intensity of an existing nitrogen XANES peak at ∼401.5 eV which was independent of the nitrogen functionality originally present in the carbon. The oxygen XANES spectra showed that carbonyl and carboxylic acid/acid anhydride functionality were also present on the surface of carbons partially gasified with oxygen. The XANES studies have also been compared with the temperatureprogrammed combustion and temperature programmed desorption studies of the carbons. The results are consistent with the presence of pyridone functionality in the partially gasified carbons. The overlap of bands may obscure the interpretation of data from X-ray absorption spectroscopy, and information is required from a number of techniques in order to provide a more detailed view.
“…Additionally, according to our previous DFT calculation of Pt/WC catalysts, the existence of Fe 3 C in the catalyst may alter the electronic structures of Pt, and then indirectly affect its catalytic activity. Regarding the reported bamboo‐like CN x nanotubes from pyridine precursor by CVD using bimetallic Fe‐Co/ γ ‐Al 2 O 3 catalyst, the possible mechanism of the formation of such bamboo‐like nitrogen‐doped CNTs was proposed to be: (i) formation of graphene‐like CN x sheets on catalysts surface; (ii) stretching the catalyst particle into conical shape; (iii) the truncated CN x cone was pushed up by the increasing strain due to the growth of the interface CN x sheets on the side surface and the recovering tendency of the catalyst to its original shape; (iv) forming a CN x nanotube by repeating (ii) and (iii). On the other hand, in this work, the amount of MIL‐100(Fe) used during the synthesis is found to significantly affect the morphology of the N‐GTs.…”
In this work, large size (i.e., diameter > 100 nm) graphene tubes with nitrogen-doping are prepared through a high-temperature graphitization process of dicyandiamide (DCDA) and Iron(II) acetate templated by a novel metal-organic framework (MIL-100(Fe)). The nitrogen-doped graphene tube (N-GT)-rich iron-nitrogen-carbon (Fe-N-C) catalysts exhibit inherently high activity towards the oxygen reduction reaction (ORR) in more challenging acidic media. Furthermore, aiming to improve the activity and stability of conventional Pt catalysts, the ORR active N-GT is used as a matrix to disperse Pt nanoparticles in order to build a unique hybrid Pt cathode catalyst. This is the first demonstration of the integration of a highly active Fe-N-C catalyst with Pt nanoparticles. The synthesized 20% Pt/N-GT composite catalysts demonstrate significantly enhanced ORR activity and H(2) -air fuel cell performance relative to those of 20% Pt/C, which is mainly attributed to the intrinsically active N-GT matrix along with possible synergistic effects between the non-precious metal active sites and the Pt nanoparticles. Unlike traditional Pt/C, the hybrid catalysts exhibit excellent stability during the accelerated durability testing, likely due to the unique highly graphitized graphene tube morphologies, capable of providing strong interaction with Pt nanoparticles and then preventing their agglomeration.
“…3, experimental time is expressed as the cumulative amount of H 2 S or SO 2 introduced into the column at constant inlet/outlet pressures, flow rates and inlet concentration (C o : 5000 ppmv for H 2 S and 3000 ppmv for SO 2 ). To compare H 2 S and SO 2 adsorption, experimental conditions were taken (vertical reactor, low W/F ratio) to avoid any elution of H2SO4 out of the fixed bed, as in the Mochida 's experimental setup [32].…”
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