Reports: ND1053582-ND10: Synthesis and Characterization of a Novel and Entirely Green Hydrogenation Catalyst: Nitrogen Oligomer
Xianqin Wang, PhD, New Jersey Institute of Technology
TPD was carried out to determine the thermal stability of the samples after synthesis using a Micromeritics® AutoChem II 2920 system. The released species during TPD are monitored with a mass spectrometer (SRS QMS200). As shown in Figure 1, with the increasing of azide concentration, both the nitrogen desorption temperature for dipped MWNT sheet and PN-MWNT sheet shifted to lower temperatures, which indicates an increasing amount of weaker attached nitrogen compounds as the azide concentration increases. Indeed, nitrogen compounds tend to occupy the sites that will form stronger interactions with MWNT for a lower overall thermodynamics free energy. For dipped MWNT sheets, initially the nitrogen desorption amount increased with the increasing of azide concentration, from 2M to 4M the desorption amount did not increase much which suggests saturation of the sites within the MWNT. However, the nitrogen desorption amount for PN-MWNT continuously increased with the increase of azide concentration, suggesting more nitrogen oligomers formed with higher azide concentrations from 0.5M to 4M. The quantities of nitrogen oligomer (Table 1) on MWNT are calculated based on the TPD results from Figure 1. This is further proved by FTIR results in Figure 2, which showed that the intensity of the peak at around 2050 cm-1 continuously increased with azide concentration.
Figure 1. TPD results for dipped MWNT sheets and PN-MWNT sheets with 0.5~4M azide concentrations for electrochemical synthesis. The
results have been normalized by sample weight.
Table 1. Corresponding nitrogen desorption amount (mmol/grams of sample) calculated by integration of the TPD results and comparing the peak areas from Figure 1 with those from injection of pure nitrogen under the same experiment conditions.
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