Probing solid state N-doping in graphene by X-ray absorption near-edge structure spectroscopy

Oxygenated monolayer carbon nitride for excellent photocatalytic hydrogen evolution and external quantum efficiency

“…The weak pre-peak A at ~285.4 eV can be assigned to the π* excitation of C=C bonds at the defect sites. 49,50 In a close comparison, a decreased intensity of feature B for O-g-C 3 N 4 monolayer can be observed when compared to that for bulk g-C 3 N 4 , suggesting the partial breaking of C-N-C structures by the introduction of oxygen. Moreover, a slight energy shift of feature B to higher energy position for O-g-C 3 N 4 monolayer can also be observed.…”

“…When the C-N-C structure is broken, the carbon sites at the edge will form C-O or C=O bonds with oxygen. Since the C=O bonds have a higher energy position of about 288.5 eV, 49,50 an energy shift can thus be seen in Figure 4a. The results are consistent with the tailoring of bulk g-C 3 N 4 into ultrathin g-C 3 N 4 sheets during which oxidized groups is formed at the edge sites of residual O-g-C 3 N 4 monolayer.…”

Scanning transmission X-ray microscopy and X-ray absorption near-edge structure studies of N-doped carbon nanotubes sealed with N2 gas

“…Obviously, the spectrum at the surface sensitive TEY mode shows three features labeled with A, B, and C, respectively. The main feature at about 407 eV (C) can be assigned to the r* excitation of C-N bonds, 15 which clearly addresses the N-doping in CNTs. A small feature around 399 eV (A) can be observed, which may result from weak amino groups or pyridinic type N-doping in CNTs.…”

“…The feature A is due to the p* excitation of carbon-carbon bonds in a carbon ring structure, the feature C to the r* excitation of carbon-carbon bonds which is also sensitive to the long range order, while the feature B to transitions to sp 3 hybridized states due to modification groups and/or surface contaminations. 13,15 The spectrum of CNTs stands for a typical case with slight oxidation or surface contaminations. 13,15 Compared to CNTs, the spectrum of NCNTs shows similar features A and B indicating a similar carbon structure.…”

“…13,15 The spectrum of CNTs stands for a typical case with slight oxidation or surface contaminations. 13,15 Compared to CNTs, the spectrum of NCNTs shows similar features A and B indicating a similar carbon structure. Because of the oxidation or surface contaminations, it is hard to separate the C-N signal for N-doping from the broad feature B.…”