3.1. The property of pristine and TM − doped B12N12
The optimized geometrical structure of the pristine B12N12 is displayed in Fig. 1. Herein, the Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, or Pt atom doping at B or N sites of B12N12 nanocages are displayed in Figs. 2 and 3, respectively. The calculated geometrical parameters are tabulated in Tables S1 and S2 of the supplementary material. The results show that the bond lengths of pristine B12N12, denoted by B3─N1, B3─N2, B3─N3, N3─B1, and N3─B2 are calculated to be 1.509, 1.509, 1.433, 1.509, and 1.509 Å, respectively. The bond angles of N1─B3─N2, N2─ B3─N3, N3─ B3─N1, B1─N3─B2, B2─N3─B3, and B3─N3─B1 are found to be 95.7, 124.4, 124.4, 83.6, 114.0, and 114.0° for the nanocage, respectively. While, the bond lengths of TMB11N12 and TMB12N11 are found in the range of 1.817 − 2.110 and 1.900 − 2.108 Å TM─N and TM─B respectively. Demonstrating that the bond lengths between the TM atoms and its adjacent B and N atoms of TM − doped B12N12 are longer than those of the B─N bond lengths of pristine B12N12. This confirms that the bond lengths at the TM atom doping sites of TM − doped B12N12 nanocages are elongated compared with the pristine nanocage. However, the bond angles of B─TM─B and N─TM─N are in the range of 59.1 − 93.0° and 69.3 − 105.9° for TM─B12N11 and TM─B11N12, respectively. Indicating that the bond angles of TMB12N11 are narrower than that of TMB11N12. In summarize, geometrical structures of the pristine B12N12 displays the dramatically structural deformation by the TM atom doping (Figs. 2 and 3).
Binding energies determined to estimate the interaction or binding strength between the TM atom and B12N12 are displayed in Table 1. The large binding energy displays a strong binding interaction between TM atom and B12N12 to form a stable complex. The binding ability of TM atom onto the B12N12 at the B site is in order: Os > Fe > Ru > Ir > Ni > Rh > Co > Pt > Pd and their binding energies are − 246.14, − 238 .17, − 235.80, − 204.05, − 190.28, − 177.56, − 165.77, − 157.67, and − 116.56 kcal/mol, respectively. While, the binding ability of TM atom onto B12N12 at the N site is in order: Os > Ir > Ru > Rh > Pt > Fe > Ni > Pd > Co and their binding energies are − 227.93, − 216.18, − 207.32, − 174.21, − 171.64, − 164.83, − 135.84, − 109.28, and − 108.09 kcal/mol, respectively. The results display that the Os atom binding on B12N12 displays the strongest binding reaction in both B and N doping sites. Moreover, the binding energies of all TM atoms onto B12N12 are negative value indicating that the doping is exothermically favorable.
Table 1
Binding energy (Eb), the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (Eg), changes of energy gap (ΔEg), percentage change of energy gap (%ΔEg), electronic chemical potential (µ), electronegativity (χ), chemical hardness (η), electrophilicity (ω), and softness (S) and TM charge of the pristine and TM − doped B12N12, computed at the B3LYP/LanL2DZ level of theory.
Species | ΔEba | EHOMOb | ELUMOb | Egb | ΔEgb | %ΔEg | µb | χb | ηb | ωb | Sb | TM chargec |
B12N12 | − | −7.876 | −1.929 | 5.947 | 0.000 | 0.00 | −4.903 | 4.903 | 2.973 | 4.042 | 0.168 | B = 1.211 |
| | | | | | | | | | | | N = − 1.211 |
FeB11N12 | −238.17 | −6.685 | −5.732 | 0.954 | 4.993 | 83.97 | −6.208 | 6.208 | 0.477 | 40.424 | 1.049 | 0.996 |
RuB11N12 | −235.80 | −6.655 | −3.423 | 3.232 | 2.715 | 45.66 | −5.039 | 5.039 | 1.616 | 7.857 | 0.309 | 0.932 |
OsB11N12 | −246.14 | −6.461 | −3.237 | 3.224 | 2.723 | 45.78 | −4.849 | 4.849 | 1.612 | 7.292 | 0.310 | 0.980 |
CoB11N12 | −165.77 | −7.477 | −4.160 | 3.317 | 2.630 | 44.23 | −5.818 | 5.818 | 1.658 | 10.208 | 0.302 | 0.900 |
RhB11N12 | −177.56 | −7.116 | −3.896 | 3.220 | 2.727 | 45.85 | −5.506 | 5.506 | 1.610 | 9.415 | 0.311 | 0.841 |
IrB11N12 | −204.05 | −6.872 | −3.692 | 3.180 | 2.767 | 46.53 | −5.282 | 5.282 | 1.590 | 8.773 | 0.314 | 0.901 |
NiB11N12 | −190.28 | −7.148 | −5.508 | 1.640 | 4.307 | 72.42 | −6.328 | 6.328 | 0.820 | 24.416 | 0.610 | 0.980 |
PdB11N12 | −116.56 | −6.404 | −5.389 | 1.015 | 4.932 | 82.94 | −5.896 | 5.896 | 0.507 | 34.263 | 0.985 | 0.857 |
PtB11N12 | −157.67 | −6.566 | −4.657 | 1.909 | 4.037 | 67.89 | −5.611 | 5.611 | 0.955 | 16.489 | 0.524 | 0.916 |
FeB12N11 | −164.83 | −7.352 | −2.844 | 4.508 | 1.439 | 24.20 | −5.098 | 5.098 | 2.254 | 5.765 | 0.222 | 0.133 |
RuB12N11 | −207.32 | −7.151 | −2.494 | 4.657 | 1.290 | 21.69 | −4.822 | 4.822 | 2.328 | 4.994 | 0.215 | −0.068 |
OsB12N11 | −227.93 | −6.964 | −2.873 | 4.090 | 1.857 | 31.22 | −4.918 | 4.918 | 2.045 | 5.914 | 0.244 | 0.001 |
CoB12N11 | −108.09 | −7.158 | −2.745 | 4.413 | 1.534 | 25.79 | −4.952 | 4.952 | 2.207 | 5.556 | 0.227 | −0.020 |
RhB12N11 | −174.21 | −7.122 | −2.542 | 4.580 | 1.367 | 22.98 | −4.832 | 4.832 | 2.290 | 5.099 | 0.218 | −0.193 |
IrB12N11 | −216.18 | −7.135 | −2.752 | 4.383 | 1.564 | 26.30 | −4.943 | 4.943 | 2.191 | 5.576 | 0.228 | −0.152 |
NiB12N11 | −135.84 | −5.573 | −2.923 | 2.651 | 3.296 | 55.43 | −4.248 | 4.248 | 1.325 | 6.808 | 0.377 | 0.211 |
PdB12N11 | −109.28 | −5.137 | −2.838 | 2.299 | 3.648 | 61.34 | −3.988 | 3.988 | 1.150 | 6.917 | 0.435 | 0.116 |
PtB12N11 | −171.64 | −5.134 | −2.899 | 2.234 | 3.713 | 62.43 | −4.017 | 4.017 | 1.117 | 7.220 | 0.448 | 0.091 |
a In kcal/mol, b In eV, c In e. |
Considering the chemical reactivity of the pristine and TM − doped B12N12, the highest occupied molecular orbital energies, the lowest unoccupied molecular orbital energies, and the energy gaps of the pristine and TM − doped B12N12 were calculated and assessed (Table 1). The calculated results point out that the Eg for TMB11N12 and TMB12N11 are found in the range of 0.954–3.317 and 2.234–4.657 eV, respectively, which are meaningfully smaller than the Eg of the pristine B12N12 (5.947 eV). Therefore, the Eg of B12N12 is significantly decreased after TM atom doping, in which its chemical reactivity is significantly increased. In addition, the chemical hardness and softness for pristine B12N12 are 2.973 and 0.168 eV, respectively. The η value of pristine B12N12 decreases to be in the range of 0.477–1.658 and 1.117–2.328 eV for TMB11N12 and TMB12N11, respectively whereas the S value of B12N12 decreases to be in the range of 0.302–1.049 and 0.215–0.448 eV for TMB11N12 and TMB12N11, respectively. Moreover, the electrophilicity of pristine B12N12 is increased after TM atom doping. The results indicate that the decreasing of the chemical hardness results in the increasing of the chemical softness which induces the decreasing of the stability of TM − doped B12N12 and this turn in increases the reactivity relative to the pristine B12N12 [33, 48].
For the pristine B12N12, the NBO charge of B and N atoms are calculated to be 1.211 and − 1.211 e, respectively, while for the TMB11N12 and TMB12N11, the TM atoms have the charge in the range of 0.841 to 0.996 and − 0.193 to 0.211 e, respectively. It is also found that TM doping affects the charge distribution within the B12N12 nanocage. This led to a meaningful decrease in the percentage change of energy gap values of the pristine to the range of 44.23 to 83.97% and 21.69 to 62.43% for the TMB11N12 and TMB12N11, respectively. The plots of the HOMO and LUMO orbital distributions of pristine B12N12 are displayed in Fig. 1 (b). From Fig. 1 (b), the HOMO and LUMO orbitals of the B12N12 are delocalized throughout the pristine B12N12 nanocage. In the case of TM − doped B12N12 nanocages, all of their HOMO and LUMO orbitals are found to be localized on the dopant atoms (Figs. 8 and 9) except for the HOMO of FeB11N12, suggested that TM atoms on TM − doped B12N12 may turn as the active electron donor site.
3.2. Adsorption of nH2 on pristine and TM − doped B12N12
The optimized structures of 1 − 4 H2 molecules adsorbed on pristine B12N12 nanocage are displayed in Fig. 4. The results display that the bond lengths of single H2 molecule adsorbed on pristine B12N12, denoted by N3─B1, N3─B2, and N3─B3 are calculated to be 1.509, 1.509, and 1.434 Å, respectively. The bond angles of B1─N3─B2, B2─N3─B3, and B3─N3─B1 are 83.5, 114.1, and 114.0° for the nanocage, respectively. It is also found that 1, 2, 3 or 4 H2 molecules can form stable complexes with B12N12. The average H─H bond length of the H2 molecules adsorbed on pristine B12N12 is calculated to be 0.744 Å which is not different with the computed result of isolated H2 molecule and is also to be in good agreement with the previous reported value (0.74 Å) [49]. The adsorption distance (AD) between a H2 molecule and the pristine B12N12 is calculated to be 2.910 Å. The average adsorption distance between the 2H2, 3H2, and 4H2 and the B12N12 are 3.068, 3.039, and 3.067 Å, respectively indicating that all average ADs are nearly the same values. Moreover, all of the bond lengths and bond angles of pristine B12N12 are slightly modified after adsorption with H2 molecules. The slight change of computed geometrical parameters of B12N12 after H2 adsorption and large adsorption distances demonstrate that the nH2 molecules can undergo weak adsorption with the pristine B12N12. This behavior is also in good consistent with the other reports in which the H2 molecule displays weak interaction with pristine nanostructures [16, 34].
The optimized structures of single H2 molecule adsorbed on TMB11N12 and TMB12N11 are displayed in Figs. 5 and 6, respectively, and their selected geometrical parameters are listed in Tables S3 and S4 of the supplementary material. The calculated results indicate that the H─H bond lengths of the single H2 molecule adsorbed on TM − doped B12N12 (0.751 − 0.889 Å) are increased, compared with the isolate H2 molecule (0.743 Å). H─H bond lengths of the H2 adsorbed on TM─doped B12N12 is longer than that of isolate H2 molecule implying the weakening of the H─H bond after adsorption. The elongation of H─H bond of H2 molecule may be due to charge transfer from TM to antibonding orbital of H2 molecule [50]. Beside, the average adsorption distances of single H2 molecule adsorbed on TMB11N12 are found in the range of 1.751–2.244 Å. Whereas the average adsorption distances of single H2 molecules adsorbed on TMB12N11 are found to be in the range of 1.822–2.343 Å. It should be noted here that the average adsorption distances of single H2 molecule adsorbed on the B site TMB11N12 are slightly shorter than that of the N site TMB12N11. As expected, the average BDs of single H2 molecule adsorbed on TM − doped B12N12 are shorter than the pristine B12N12 approving that TM doping can improve H2 adsorption ability of B12N12 nanomaterial. The results confirm that the TM doping displays the important and effective role for improve the adsorption ability of B12N12 onto H2 molecule, which is compatible with the previous reports of the H2 molecule adsorbed on TM–doped BNNS [51], TM–doped SiCNT [52], and TM–doped GS [53].
Moreover, the optimized structures of nH2 (n = 2 − 4) molecules adsorbed on TM − doped B12N12 are displayed in Figs. S1 − S6 of the supplementary material. According to the above results, it is reasonable to consider that the maximum storage number of H2 molecules on the first adsorption layer for the most of TMB11N12 and TMB12N11 is three hydrogen molecules, except for PdB11N12, PdB12N11, PtB11N12, PtB12N11, and NiB12N11, the maximum storage number of H2 molecules on the first adsorption layer of them is two H2 molecules. Considering the adsorption abilities of nH2 (n = 1 − 4) molecules on the pristine and TM − doped B12N12 as presented in Table 2, the adsorption energies of H2, 2H2, 3H2, and 4H2 molecules adsorbed on the pristine B12N12 are found to be − 0.63, − 0.67, − 0.65, and − 0.54 kcal/mol, respectively. The small Eads values indicate that the pristine B12N12 is slightly sensitive to the nH2 adsorption, corresponding to the large average adsorption distance. The Eads values of H2/TMB11N12, 2H2/TMB11N12, 3H2/TMB11N12, and 4H2/TMB11N12 are found in the range of − 17.66 to − 2.98, − 16.22 to − 2.48, − 14.94 to − 2.42, and − 11.30 to − 1.91 kcal/mol, respectively. The results indicate that the OsB11N12 display stronger interaction with the nH2 molecules than the other TMB11N1 in which its optimized structures are displayed in Fig. 7, while the NiB11N12 display weaker interaction with the nH2 molecules than the other TM atom doping. The Eads values of H2/TMB12N11, 2H2/TMB12N11, 3H2/TMB12N11, and 4H2/TMB12N11 are found in the range of − 8.99 to − 3.08, − 9.86 to − 3.12, − 10.05 to − 2.21, and − 6.98 to − 1.79 kcal/mol, respectively. The results suggest that the FeB12N11 displays the strongest interaction with the H2, 2H2, and 4H2 molecules, whereas the CoB12N11 displays the strongest interaction with the 3H2 molecules compared with the other TMB12N11. The increase of H2 adsorption energies of B12N12 by the TM doping verifies that TM doping can improve H2 adsorption ability of B12N12 nanomaterial to be applied its as hydrogen storage nanomaterial.
Table 2
Adsorption energy (Eads) and average adsorption distance (AD) of hydrogen molecules adsorbed on pristine and TM − doped B12N12, computed at the B3LYP/LanL2DZ level of theory.
Species | H2 | | 2H2 | | 3H2 | | 4H2 |
Eadsa | ADb | | Eadsa | ADb | | Eadsa | ADb | | Eadsa | ADb |
B12N12 | −0.63 | 2.910 | | −0.67 | 3.069 | | −0.65 | 3.040 | | −0.54 | 3.068 |
FeB11N12 | −4.79 | 2.111 | | −4.14 | 2.107 | | −4.12 | 2.092 | | −3.32 | 2.478 |
RuB11N12 | −6.74 | 2.051 | | −7.70 | 1.984 | | −8.17 | 1.966 | | −6.30 | 2.462 |
OsB11N12 | −17.66 | 1.751 | | −16.22 | 1.818 | | −14.94 | 1.845 | | −11.30 | 2.526 |
CoB11N12 | −3.65 | 2.042 | | −3.16 | 2.089 | | −3.42 | 2.086 | | −2.75 | 2.480 |
RhB11N12 | −6.59 | 1.978 | | −6.45 | 1.988 | | −5.82 | 2.029 | | −4.55 | 2.470 |
IrB11N12 | −13.26 | 1.805 | | −12.29 | 1.843 | | −10.94 | 1.881 | | −8.39 | 2.339 |
NiB11N12 | −2.98 | 2.244 | | −2.48 | 2.288 | | −2.42 | 2.299 | | −1.91 | 2.654 |
PdB11N12 | −7.44 | 2.012 | | −4.40 | 2.113 | | −3.18 | 2.423 | | −3.81 | 2.809 |
PtB11N12 | −10.64 | 1.859 | | −6.23 | 1.936 | | −4.36 | 2.456 | | −5.65 | 2.726 |
FeB12N11 | −8.91 | 1.834 | | −9.86 | 1.750 | | −9.07 | 1.797 | | −6.98 | 2.354 |
RuB12N11 | −5.23 | 2.098 | | −3.92 | 2.107 | | −5.16 | 2.010 | | −3.94 | 2.532 |
OsB12N11 | −4.91 | 2.106 | | −7.74 | 1.948 | | −7.80 | 1.897 | | −5.95 | 2.560 |
CoB12N11 | −8.41 | 1.822 | | −9.78 | 1.724 | | −10.05 | 1.736 | | −7.71 | 2.353 |
RhB12N11 | −4.68 | 2.118 | | −4.79 | 2.008 | | −4.81 | 2.022 | | −3.76 | 2.567 |
IrB12N11 | −6.35 | 2.028 | | −6.52 | 1.926 | | −6.77 | 1.942 | | −5.23 | 2.653 |
NiB12N11 | −7.10 | 1.844 | | −6.49 | 1.871 | | −4.56 | 2.246 | | −3.53 | 2.654 |
PdB12N11 | −3.67 | 2.268 | | −3.33 | 2.217 | | −2.36 | 2.658 | | −1.91 | 3.005 |
PtB12N11 | −3.08 | 2.343 | | −3.12 | 2.211 | | −2.21 | 2.823 | | −1.79 | 3.029 |
a In kcal/mol, b In Å. |
In order to better understand the adsorption abilities of nH2 adsorbed to TM − doped B11N12 and B12N11, the electronic properties of all optimized structures were calculated. The partial charge transfers during the adsorption process of pristine or TM − doped B12N12 with hydrogen molecules were estimated and the loss and gain of the electron were also examined by natural bond orbital calculations implemented in the GAUSSIAN 09 program package [42]. The PCTs of H2 molecule adsorbed on pristine and TM − doped B12N12 are shown in Table 3 and the PCTs of nH2 molecules (n = 2 − 4) adsorbed on pristine and TM − doped B12N12 are shown in Tables S5 − S7 of the supplementary material. According to the PCT data, the partial charges are slightly transfer from nH2 molecules to pristine B12N12 in the range of 0.010 − 0.027 e, except for the single hydrogen molecule which do not transfer charge between hydrogen and pristine B12N12. Basically, the small Eads, small charge transfer, and long bond distance reveal that H2 molecules undergo weak the adsorption on the pristine B12N12. All partial charges for nH2/TM − doped B12N12 are transferred from the nH2 molecules to the TM − doped B12N12 due to the positive charge values. The PCT values of nH2/TM − doped B12N12 are found in the range of 0.052 to 0.931 e, corresponds to the large Eads, large charge transfer, and short bond distance undergo strong adsorption on the TM − doped B12N12.
Table 3
The highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (Eg), changes of energy gap (ΔEg), percentage change of energy gap (%ΔEg), electronic chemical potential (µ), electronegativity (χ), chemical hardness (η), electrophilicity (ω), and softness (S) partial charge transfer (PCT) of H2 molecule adsorbed on the pristine and TM − doped B12N12, computed at the B3LYP/LanL2DZ level of theory.
Species | EHOMOa | ELUMOa | Ega | ΔEga | %ΔEg | µa | χa | ηa | ωa | Sa | PCTb |
H2/B12N12 | −7.881 | −1.939 | 5.942 | 0.005 | 0.09 | −4.910 | 4.910 | 2.971 | 4.057 | 0.168 | 0.000 |
H2/FeB11N12 | −6.433 | −5.859 | 0.574 | 0.380 | 39.84 | −6.146 | 6.146 | 0.287 | 65.846 | 1.743 | 0.097 |
H2/RuB11N12 | −6.545 | −3.497 | 3.048 | 0.184 | 5.68 | −5.021 | 5.021 | 1.524 | 8.272 | 0.328 | 0.118 |
H2/OsB11N12 | −6.711 | −3.437 | 3.274 | −0.050 | −1.55 | −5.074 | 5.074 | 1.637 | 7.863 | 0.305 | 0.200 |
H2/CoB11N12 | −7.328 | −4.131 | 3.197 | 0.119 | 3.59 | −5.730 | 5.730 | 1.599 | 10.268 | 0.313 | 0.108 |
H2/RhB11N12 | −7.084 | −4.004 | 3.080 | 0.140 | 4.35 | −5.544 | 5.544 | 1.540 | 9.980 | 0.325 | 0.137 |
H2/IrB11N12 | −6.982 | −3.933 | 3.049 | 0.131 | 4.12 | −5.457 | 5.457 | 1.524 | 9.768 | 0.328 | 0.201 |
H2/NiB11N12 | −5.266 | −3.554 | 1.712 | −0.072 | −4.40 | −4.410 | 4.410 | 0.856 | 11.360 | 0.584 | 0.065 |
H2/PdB11N12 | −7.150 | −4.606 | 2.544 | −1.529 | −150.68 | −5.878 | 5.878 | 1.272 | 13.584 | 0.393 | 0.109 |
H2/PtB11N12 | −6.993 | −4.220 | 2.773 | −0.863 | −45.20 | −5.606 | 5.606 | 1.386 | 11.336 | 0.361 | 0.170 |
H2/FeB12N11 | −6.886 | −2.753 | 4.134 | 0.374 | 8.31 | −4.820 | 4.820 | 2.067 | 5.619 | 0.242 | 0.109 |
H2/RuB12N11 | −7.262 | −2.581 | 4.682 | −0.025 | −0.53 | −4.922 | 4.922 | 2.341 | 5.174 | 0.214 | 0.084 |
H2/OsB12N11 | −6.863 | −2.902 | 3.961 | 0.129 | 3.16 | −4.883 | 4.883 | 1.980 | 6.019 | 0.252 | 0.102 |
H2/CoB12N11 | −7.171 | −2.719 | 4.452 | −0.039 | −0.88 | −4.945 | 4.945 | 2.226 | 5.492 | 0.225 | 0.124 |
H2/RhB12N11 | −7.084 | −2.409 | 4.676 | −0.096 | −2.09 | −4.746 | 4.746 | 2.338 | 4.818 | 0.214 | 0.088 |
H2/IrB12N11 | −7.176 | −2.727 | 4.449 | −0.066 | −1.51 | −4.952 | 4.952 | 2.224 | 5.512 | 0.225 | 0.114 |
H2/NiB12N11 | −5.525 | −2.710 | 2.815 | −0.165 | −6.21 | −4.117 | 4.117 | 1.408 | 6.022 | 0.355 | 0.101 |
H2/PdB12N11 | −5.094 | −2.787 | 2.307 | −0.008 | −0.33 | −3.941 | 3.941 | 1.153 | 6.732 | 0.434 | 0.052 |
H2/PtB12N11 | −5.076 | −2.856 | 2.220 | 0.014 | 0.65 | −3.966 | 3.966 | 1.110 | 7.084 | 0.450 | 0.054 |
a In eV, b In e. |
In addition, the EHOMO, ELUMO, Egap, and ΔEgap of the most stable structures of the pristine and TM − doped B12N12 and their H2 adsorption are considered (Tables 3, S5 − S7). It is found that, the Egap of the difference number of H2 molecules adsorbed on pristine B12N12 are found in the range of 5.942 to 5.949 eV, which remains unchanged (Egap of B12N12 = 5.947 eV). It is proposed that the hydrogen molecule does not affect the Egap of pristine B12N12 nanocage. So, the electrical conductivity pristine B12N12 do not vary with H2 molecule adsorptions and the pristine B12N12 poorly detect the H2 molecules. For nH2 molecule adsorption on the TM − doped B12N12 systems, it is clearly seen that the Egap of TM − doped B12N12 systems are decreased meaning the change in the Egap value is primary criterion for arbitrating the potential of a complex to be used as a gas sensor. The significant changes of energy gaps (ΔEg) and percentage change of energy gaps (%ΔEg) of TM − doped B12N12 systems after nH2 molecule adsorption confirm this behavior. The same behavior is found in good agreement with the previous work that molecular adsorption affects the conductivity of C − and Be − doped B12N12 nanocages [35]. Then the results point out that the TM − doped B12N12 substrate can be used as a potential gas sensor to detect H2 molecules.
The electronic chemical potential, electronegativity, chemical hardness, electrophilicity, and softness for the pristine B12N12 do not change significantly after interaction with nH2 molecules (Tables 3, S5 − S7). Whereas the electronic chemical potential, electronegativity, chemical hardness, electrophilicity, and softness for the TM − doped B12N12 are changed after hydrogen adsorption. The results suggest that TM doping can modify conductivity of B12N12, while H2 molecule adsorption can also modify the conductivity of TM − doped B12N12. In addition, the HOMO and LUMO orbital distributions of hydrogen adsorptions on TM − doped B12N12 plotted and presented. The plots of HOMO and LUMO orbital distributions of the single H2 molecule adsorbed on TM − doped B12N12 are displayed in Figs. 10 − 11. The HOMO and LUMO orbitals of hydrogen adsorbed on TM − doped B12N12 are found to be localized throughout the doping sites as well as adsorption sites, indicating the electron conduction through these systems, except for the HOMO and LUMO of FeB11N12 are delocalized on the B and N atoms.
To make further exploration of electronic properties, the density of states (DOS) were also computed and plotted. The DOS of H2 molecule adsorption on pristine and TM − doped B11N12 and B12N11 were calculated to understand the change of their electronic structures. The DOS of H2 adsorbed on pristine B12N12 and OsB11N12 is shown Fig. 12. It was found that the DOS of pristine B12N12 is slightly modified by H2 molecule adsorption. This confirms that H2 molecule is not sensitive to the electronic properties of the pristine B12N12. Whereas the DOSs of H2 adsorbed on TM − doped B12N12 are displayed in Figs. S7 − S8 of the supplementary material. After hydrogen adsorbed on TM − doped B11N12 and B12N11, it is found that their DOSs are also noticeably changed with unsymmetric distributions, especially the DOS of OsB11N12 is significantly changed by H2 molecule adsorption (see Fig. 12). Therefore, the change in the DOSs of TM − doped B12N12 by H2 adsorption confirms that TM − doped B12N12 may be applied as an effective nanomaterial for H2 detection.