Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes

Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes 1 2 first-author 2 2 corresp Corresponding authors. E-mail address: liuwenguan@sinap.ac.cn Corresponding authors. E-mail address: liuwenguan@sinap.ac.cn liuwenguan@sinap.ac.cn 3 2 4 2 1 1 2 corresp Corresponding authors. E-mail address: wushengwei@sinap.ac.cn Corresponding authors. E-mail address: wushengwei@sinap.ac.cn wushengwei@sinap.ac.cn 2 School of Mathematics and Physics, University of South China, Hunan, Hengyang 421001, China School of Mathematics and Physics, University of South China, Hunan, Hengyang 421001, China Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, Zhuhai 519082, China Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, Zhuhai 519082, China Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei 230031, China Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei 230031, China Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H 2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene. Hydrogen Graphene Single vacancy Double vacancy Adsorption Desorption First-principles calculation 1. Introduction 1 Storage of hydrogen, as one of the clean alternative energy resources with highest energy content by weight [ 1 1 ], has been investigated in metal hydrides [ 2 2 , 3 3 ], alloys [ 4 4 - 7 7 4-7 ], and porous substances [ 8 8 , 9 9 ], and is found to be particularly promising in graphene [ 10 10 – 20 20 10–20 ], which has excellent electronic, mechanical, and thermal properties [ 21 21 , 22 22 ], as well as the special characteristic of reversible hydrogenation–dehydrogenation reactions [ 23 23 ]. The hydrogen isotope tritium is one of the most important initial radiological activities of irradiated graphite waste after reactor shutdown [ 23 23 ] and therefore, tritium desorption from such phenomenon becomes one of the crucial targets of decontamination of nuclear graphite. Tritium has adsorption, diffusion, and desorption properties similar with hydrogen; for this reason, fundamental understanding of the adsorption/desorption of hydrogen molecules and the migration mechanism of H atoms on graphene surface is of particular importance [ 24 24 ]. Nevertheless, the dissociation rate of H 2 molecules on pristine graphene is too low as it goes through to physisorption, while the dissociation energy barrier is very high (2.7-3.3eV) [ 25 25 , 26 26 ]. Compared to pristine graphene (or graphene-like materials), adsorption and desorption of H 2 are easier on graphene (or graphene-like materials) with defects [ 24 24 , 27 27 - 37 37 27-37 ]. Nonetheless, such various defects, including the adsorption property of electromagnetic waves [ 38 38 - 40 40 38-40 ], dielectric property [ 41 41 ], and so on, affect the properties and performance of graphene. Studies have shown that the adsorbing capacity of toxic gases (NO, CO, HCN, and SO 2 ) [ 42 42 ] and reactive gases (CO and O 2 ) [ 43 43 - 46 46 43-46 ] on graphene (or graphene-like materials) can be regulated by doping, and that vacancies as common defects, reduces the adsorption energy of adsorbents, such as sodium [ 47 47 ] and H atoms [ 48 48 ], so that graphenes with vacancy defects have attracted considerable research attention [ 28 28 - 37 37 28-37 ]. Vacancy defects in graphene can enhance its reactivity and affect charge distributions, and are always found to be sites of chemisorption [ 24 24 ]; they are classified into single vacancy (SV), double vacancy (DV), among others [ 49 49 - 52 52 49-52 ]. SV is identified to promote the dissociation of H 2 molecules with reduced activation barrier energy of 0.63 eV, as compared to 2.38 eV for pristine graphene [ 53 53 ]. An isolated SV in a graphene can bind four H atoms stably or even six, to form a metastable and magnetic structure at room temperature [ 53 53 ]. On one hand, successive adsorption reaction of H 2 on SV has been studied [ 48 48 , 54 54 , 55 55 ], especially in Ref. [ 48 48 ], where a detailed map of the continuous process of hydrogenation was demonstrated systematically. On the other hand, the reversible hydrogenation–dehydrogenation reactions have been discussed in Sunnardianto et al., who reported on a reversible hydrogen-dissociative adsorption on a SV graphene that absorbs two H atoms [ 55 55 ]; they further stated minimum energy pathways and activation barriers for both adsorption and desorption of one H 2 molecule on triple-hydrogenated vacancy graphene that suggests a potential application for hydrogen storage [ 56 56 ]. The focus of previous research to date was on SV graphene, while rare attention has been paid to DV graphene, which has better thermal stability and thus, is thermodynamically favored over the former, aside from its vacancies having even number of missing atoms being more stable than those with odd number of missing atoms [ 49 49 - 51 51 49-51 ]. In this paper, we utilized first-principles calculation to study the behaviors of hydrogen adsorption, diffusion, and desorption on both SV and DV graphenes, which could provide theoretical guidance for both hydrogen storage by use of graphene and thermal desorption of tritium from decommissioned nuclear graphite. 2. Computational methods 1 All calculations were performed via density functional theory method [ 57 57 , 58 58 ] implemented in the Vienna Ab Initio Simulation Package (VASP) [ 59 59 ]. Exchange and correlation effects were treated self-consistently with a generalized gradient approximation (GGA) [ 60 60 ]. To describe the electron-ion interaction, the projector augmented wave (PAW) pseudo-potential [ 61 61 ] was employed. Cut-off energy for the plane wave basis was set at 450 eV to ensure good convergence. Geometry optimization was performed with force convergence criterion of 0.01 eV/Å, while energy convergence criterion was 10 -6 eV. Diffusion and desorption energy barriers were estimated through the climbing image nudged elastic band (CI-NEB) method [ 62 62 - 64 64 62-64 ]. The Brillouin zone was sampled with a grid of 4×4×1 k-points, with the lattice constant of optimized graphene set to 2.462 Å, which is in good agreement with other theoretical and experimental values [ 65 65 , 66 66 ]. A 6 × 6 hexagonal supercell containing 72 carbon atoms was used to model the graphene in all the calculations. Periodic boundary conditions were adopted in all three directions and the size of supercell in the z-axis (i.e. the thickness of the vacuum) was set at 18.75 Å. The reaction energy for adsorbing n H atoms on the graphene is computed as [ 48 48 ] <math display="block" id="M1"><mrow><mi>Δ</mi><msub><mi>E</mi><mi>n</mi></msub><mo>=</mo><msub><mi>E</mi><mrow><mi>V</mi><msub><mi>H</mi><mi>n</mi></msub></mrow></msub><mo>−</mo><msub><mi>E</mi><mi>V</mi></msub><mo>−</mo><msub><mi>E</mi><mrow><mi>n</mi><mi>H</mi></mrow></msub><mo>,</mo></mrow></math> where the three terms on the right are the total energy of the graphene supercell with n -times hydrogenated vacancy, the energy of the graphene supercell with bare vacancy, and the reference state of n H atoms, respectively. The reaction energy for sequential adsorption <math id="M2"><mrow><mi>Δ</mi><mi>Δ</mi><msub><mi>E</mi><mi>n</mi></msub></mrow></math> is defined similarly as [ 48 48 ] <math display="block" id="M3"><mrow><mi>Δ</mi><mi>Δ</mi><msub><mi>E</mi><mi>n</mi></msub><mo>=</mo><mi>Δ</mi><msub><mi>E</mi><mi>n</mi></msub><mo>−</mo><mi>Δ</mi><msub><mi>E</mi><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>=</mo><msub><mi>E</mi><mrow><mi>V</mi><msub><mi>H</mi><mi>n</mi></msub></mrow></msub><mo>−</mo><msub><mi>E</mi><mrow><mi>V</mi><msub><mi>H</mi><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub></mrow></msub><mo>−</mo><msub><mi>E</mi><mi>H</mi></msub><mo>,</mo></mrow></math> where <math id="M4"><mrow><mi>Δ</mi><msub><mi>E</mi><mrow><mi>n</mi><mtext>-</mtext><mn>1</mn></mrow></msub></mrow></math> refers to the ( n-1 )-times hydrogenated state. As validation, we simulated the adsorption, migration, and desorption behaviors of H atoms on pristine graphene. Results showed an adsorption energy of 0.73 eV, which agrees well with the other theoretical values [ 67 67 , 68 68 ], and desorption energy barrier of 2.55 eV, which also coincides with those of previous studies [ 26 26 , 69 69 ]. 3. Results and discussion 1 3.1 SV and DV graphene structures 2 The calculation model of the SV graphene was constructed from a carbon atom extracted from the 6 × 6 hexagonal supercell, then the bare vacancy underwent a Jahn–Teller distortion, with two of the three carbon atoms in it forming a C–C bond [ 50 50 , 70 70 - 73 73 70-73 ]. Likewise, the DV graphene model was formed from the 6 × 6 hexagonal supercell by extracting two carbon atoms in different ways. Calculation models of SV, DV5-8-5, DV555-777, and DV5555-6-7777 graphenes [ 49 49 - 52 52 49-52 ] after structure optimization are shown in Fig. 1 Fig. 1 . The simplest DV graphene was DV5-8-5, which contains two pentagons and one octagon; the most stable was DV555-777 [ 74 74 ] with three pentagons and three heptagons and; DV5555-6-7777 had four pentagons, one hexagon, and four heptagons. No dangling bonds were present in these three DV structures unlike in the SV structure. Simulation results illustrated that the top site of the carbon atom in the DV structures was a stable adsorption site. 3.2 Hydrogen adsorption and desorption on SV graphenes 2 Figure 2 Figure 2 shows a detailed map of optimized hydrogenated SV graphene structures, in which the calculated energies were compared with the results in Ref. [ 48 48 ] (shown in blue inside parentheses in Fig. 2 Fig. 2 ). Only the energetically favorable process of continuous hydrogenation in SV graphene is depicted in the figure. In general, the resulting adsorption energies in Fig. 2 Fig. 2 coincide with those in Ref. [ 48 48 ]. In the SV graphene, a first H atom was preferentially absorbed by the C atom with a dangling bond, i.e., C1 in the Fig. 1(a) Fig. 1(a) , which is strongly exothermic, and the adsorption energy was -4.35 eV, slightly higher than -4.42 eV [ 48 48 ], but significantly lower than -3.45 eV [ 53 53 ]. When adsorbing a second H atom, along with the initial atom they could be located either on the same or on different sides, with the most energetically favorable configuration labels of SV 11(u-u) and SV 11(u-d) . After absorption of a third H atom, the most stable structure becomes SV 111(u-u-d) (each of the three vacant C atoms bonding with one H atom and one of the three H atoms, are oriented differently). From Fig. 2 Fig. 2 , the SV 111(u-u-d) configuration could transform into SV 211(ud-d-d) through adsorption of a fourth H atom at -2.42 eV, which again, agrees with Ref. [ 48 48 ]. Nevertheless, SV 111(u-u-d) was also found to transform to SV 211(uu-u-d) by adsorbing a fourth H atom at the energy of -2.71 eV, which is not found in Ref. [ 48 48 ] and which was even lower than that in SV 211(ud-d-d) (-2.42 eV), so that SV 211(uu-u-d) was as important as SV 211(ud-d-d) . Unfortunately, the SV 211(uu-u-d) configuration is yet to be studied. After absorption of the fifth H atom, SV 221(ud-ud-u) , SV 221(uu-ud-d) , and SV 221(uu-uu-d) form, as demonstrated in Fig. 2 Fig. 2 . Desorption of hydrogen molecule from SV 221(ud-ud-u) to form SV 111 , and in turn, adsorption of hydrogen molecule in SV 111 to form SV 221(ud-ud-u) have been investigated in Ref. [ 56 56 ], in which the energy barrier of these reactions was 1.3 eV, which means this storage and release concept has the potential to act as a hydrogen storage system. Furthermore, in this work, first-principles calculations were used to study the energy pathways and barriers of the reactions, i.e., SV 111 + H 2 ↔ SV 221(uu-ud-d) and SV 111 + H 2 ↔ SV 221(uu-uu-d) . Minimum energy pathways for SV 221(uu-ud-d) ↔ SV 111(u-d-d) +H 2 and SV 221(uu-uu-d) ↔ SV 111(u-u-d) +H 2 are shown in Fig. 3 Fig. 3 . The energy barriers of H 2 desorption and adsorption for SV 221(uu-ud-d) ↔ SV 111(u-d-d) +H 2 and for SV 221(uu-uu-d) ↔ SV 111(u-u-d) +H 2 were 1.85 eV and 1.92 eV, and 2.17 eV and 2.26 eV, respectively. All energy barriers of these two reactions were apparently higher than those for SV 221(ud-ud-u) ↔ SV 111(u-u-d) +H 2 (i.e., 1.30 eV [ 56 56 ]), but their desorption energy barriers were lower than those for SV 2(u-u) → SV+H 2 (i.e., 4.06 eV [ 53 53 ]) and their adsorption energy barriers were significantly higher than those for SV+H 2 →SV 2(u-u) (i.e., 0.63eV [ 53 53 ]). As a result, H 2 desorption and adsorption were more difficult in SV 221(uu-ud-d) ↔ SV 111(u-d-d) +H 2 and SV 221(uu-uu-d) ↔ SV 111(u-u-d) +H 2 than in SV 221(ud-ud-u) ↔ SV 111(u-u-d) +H 2 , and these two reactions could not be identified as potential hydrogen storage reactions. 3.3 Adsorption, migration, and desorption of hydrogen on DV graphene 2 Figure 1 Figure 1 illustrates the stable adsorption sites with high symmetry in DV5-8-5, DV555-777 and DV5555-6-7777. Adsorption energies of hydrogen in these sites were calculated and are shown in Table 1 Table 1 , where the adsorption energies of H atoms observed on the DV region were mostly lower than those away from the region. For example, the adsorption energy of an H atom in T 2 site of DV555-777 (i.e., -2.51 eV) was apparently lower than in the T 6 site (i.e., -1.31 eV). This indicated that H atoms have an evident tendency to diffuse to the region of double vacancy from outside. The adsorption, migration, and desorption behaviors of H atoms in these DVs were studied and are shown in Figs. 4, 5, Figs. 4, 5, and 6 6 . 1 1 Substrates 1 1 Sites 1 1 E ad (eV) 1 1 DV5-8-5 1 1 T 1 1 1 -1.22 1 1   1 1 T 2 1 1 -2.31 1 1   1 1 T 3 1 1 -1.57 1 1   1 1 T 4 1 1 -1.23 1 1 1 1 T 5 1 1 -0.97 1 1   1 1 T 6 1 1 -1.23 1 1   1 1 T 7 1 1 -1.65 1 1   1 1 T 8 1 1 -1.18 1 1 DV555-777 1 1 T 1 1 1 -1.18 1 1   1 1 T 2 1 1 -2.51 1 1 1 1 T 3 1 1 -1.95 1 1 1 1 T 4 1 1 -1.86 1 1 1 1 T 5 1 1 -1.60 1 1 1 1 T 6 1 1 -1.31 1 1 DV5555-6-7777 1 1 T 1 1 1 -1.40 1 1   1 1 T 2 1 1 -2.14 1 1 1 1 T 3 1 1 -1.82 1 1 1 1 T 4 1 1 -1.51 1 1 1 1 T 5 1 1 -1.47 1 1 1 1 T 6 1 1 -1.83 1 1 1 1 T 7 1 1 -1.90 1 1 1 1 T 8 1 1 -1.53 1 1 1 1 T 9 1 1 -1.33 1 1 1 1 T 10 1 1 -1.12 In DV5-8-5, the region of double vacancies mainly had an octagon ring and two pentagon rings; in DV555-777, the vacancy region was made up of three octagon and three pentagon rings and; in DV5555-6-7777, the region was composed of four octagon and two pentagon rings, and one hexagon ring. Hence, the order of the vacancy size was DV5555-6-7777>DV555-777>DV5-8-5, which could influence the capacity of hydrogen adsorption on these structures. According to the calculated adsorption energies in Table 1 Table 1 , the most stable site in DV5-8-5 was T 2 , as shown in Figs. 1(b) Figs. 1(b) and 4 4 , which was the top site of the carbon atom shared by a pentagon, a hexagon and an octagon ring. Hydrogen adsorption energy in this site was -2.31 eV, and the first adsorbed H atom was bound to occupy this site. The second most stable site in DV5-8-5 was not T 1 in the octagon ring, but T 3 with adsorption energy of -1.57 eV. It was clear from Table 1 Table 1 that the adsorption sites (e.g., T 2 and T 3 ) in DV5-8-5 were more stable than those away from the vacancy (e.g., T 8 ), which justified the tendency of H atoms to accumulate in the vacancy region of DV5-8-5. Adsorption and desorption of H 2 molecules on/from DV5-8-5 are shown in Fig. 4 Fig. 4 . Before the desorption process, two H atoms should gather together in the DV5-8-5; the first atom was adsorbed in T 2 , while the second was assumed to migrate along the path of T 5 →T 4 →T 3 to T 3 , which is the second most stable site. Two steps occurred during this migration at energy barriers of 1.21 eV and 0.49 eV, as shown in Fig. 4 Fig. 4 . The possible desorption of H 2 molecule from DV5-8-5 was investigated, where the system energy decreased by 0.21 eV after dehydrogenating; Nevertheless, the reaction energy barrier was found to be 2.10 eV, which means that desorption of H 2 molecule was difficult. For the adsorption of H 2 molecule on DV5-8-5, the energy barrier was 2.31 eV, close to the value on pristine graphene (i.e., 2.38 eV) [ 53 53 ], which is mainly induced by the absence of dangling bonds in both DV5-8-5 and pristine graphene. From Table 1 Table 1 , the most stable site in DV555-777 was that of T 2 at adsorption energy of -2.51 eV. Interestingly, T 2 was not the center of DV555-777, as shown in Fig. 1 Fig. 1 ; the center site T 1 , however, was the most energetically unfavorable energetically, as observed in Table 1 Table 1 , with adsorption energy of -1.18 eV. Figure 5 Figure 5 shows the adsorption and desorption of H 2 molecules on/from DV555-777. The first H atom was adsorbed in T 2 , while the second was supposed to diffuse along the path of T 6 →T 4 →T 3 to T 3, which was the second most stable site and was adjacent to T 2 . From the figure, the energy barriers of the two-step migration were 0.74 eV and 0.71 eV, respectively. The energy barriers of H 2 desorption and adsorption were calculated at 2.23 eV and 2.55 eV, respectively. Hence, while migration for H 2 molecule was relatively easy, desorption and adsorption from/on DV555-777 was otherwise difficult. For the configuration of DV5555-6-7777 in Table 1 Table 1 , T 2 was the most stable site with -2.14 eV energy of adsorption, and thus, the first H was adsorbed in this site. The second H was assumed to migrate through T 10 →T 4 →T 3 to T 3 , which was a relatively stable site adjacent to T 2 , and where the corresponding energy barriers were 0.69 eV and 0.97 eV, respectively, as shown in Fig. 6 Fig. 6 . As in the cases of DV5-8-5 and DV555-777, H 2 molecule adsorption and desorption from/on DV5555-6-7777 was also difficult, because the energy barriers for these processes were 2.10 and 2.76 eV, respectively, as in Fig. 6 Fig. 6 . 4. Conclusion 1 First-principles calculations were performed for investigation of adsorption and desorption processes of hydrogen from SV and DV graphenes. In SV graphene, continuous hydrogenation was an energetically favorable process, and the minimum energy pathways were calculated by SV 221(uu-ud-d) ↔ SV 111(u-d-d) +H 2 and SV 221(uu-uu-d) ↔ SV 111(u-u-d) +H 2 . In DV graphene, adsorption energies of H atoms on the region of double vacancy were generally lower than those away from the region, and the corresponding energy barriers for H diffusion into the vacancy were relatively low as well. Based on these energy barriers, desorption and adsorption of H 2 molecules from/on DV graphenes was difficult. This work provides a comprehensive understanding of adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes, and can serve as theoretical guidance for both hydrogen storage on graphene and thermal desorption of tritium from decommissioned nuclear graphite. References I. Staffell , The energy and fuel data sheet . 2011 . http://tinyurl.com/energydata http://tinyurl.com/energydata The energy and fuel data sheet P.D. Jongh , M. Allendorf , J.J. Vajo et al ., Nanoconfined light metal hydrides for reversible hydrogen storage . MRS Bull . 38 , 488 - 494 ( 2013 ). doi: 10.1557/mrs.2013.108 http://doi.org/10.1557/mrs.2013.108 Nanoconfined light metal hydrides for reversible hydrogen storage L. Pickering , J. Li , D. Reed et al ., Ti-V-Mn based metal hydrides for hydrogen storage . J. Alloys Compd . 580 , 233 - 237 ( 2013 ). doi: 10.1016/j.jallcom.2013.03.208 http://doi.org/10.1016/j.jallcom.2013.03.208 Ti-V-Mn based metal hydrides for hydrogen storage Jr A.M. Jorge ., E. Prokofiev , G.L. de Lima , et al ., An investigation of hydrogen storage in a magnesium-based alloy processed by equal-channel angular pressing . Int. J. Hydrogen Energy 38 , 8306 - 8312 ( 2013 ). doi: 10.1016/j.ijhydene.2013.03.158 http://doi.org/10.1016/j.ijhydene.2013.03.158 An investigation of hydrogen storage in a magnesium-based alloy processed by equal-channel angular pressing D.L. Chao , C.L. Zhong , Z.W. Ma et al ., Improvement in high-temperature performance of Co-free high-Fe AB 5-type hydrogen storage alloys . Int. J. Hydrogen Energy 37 , 12375 - 12383 ( 2012 ). doi: 10.1016/j.ijhydene.2012.05.147 http://doi.org/10.1016/j.ijhydene.2012.05.147 Improvement in high-temperature performance of Co-free high-Fe AB 5-type hydrogen storage alloys C.N. Peng , The effects of hydrogen on the helium behavior in palladium . Nucl. Sci. Tech . 27 , 105 - 110 ( 2016 ). doi: 10.1007/s41365-016-0115-5 http://doi.org/10.1007/s41365-016-0115-5 The effects of hydrogen on the helium behavior in palladium W.G. Liu , Y. Qian , D.X. Zhang et al ., Theoretical study of the interaction between hydrogen and 4d alloying atom in nickel . Nucl. Sci. Tech . 28 , 81 - 84 ( 2017 ). doi: 10.1007/s41365-017-0235-6 http://doi.org/10.1007/s41365-017-0235-6 Theoretical study of the interaction between hydrogen and 4d alloying atom in nickel P. Reunchan , S.H. Jhi , Metal-dispersed porous graphene for hydrogen storage . Appl. Phys. Lett . 98 , 93 - 103 ( 2011 ). doi: 10.1063/1.3560468 http://doi.org/10.1063/1.3560468 Metal-dispersed porous graphene for hydrogen storage Y. Xia , Z. Yang , Y. Zhu , Porous carbon-based materials for hydrogen storage: advancement and challenges . J. Mater Chem. A 1 , 9365 - 9381 ( 2013 ). doi: 10.1039/c3ta10583k http://doi.org/10.1039/c3ta10583k Porous carbon-based materials for hydrogen storage: advancement and challenges X.K. Chen , J. Liu , Z.H. Peng et al , A wave-dominated heat transport mechanism for negative differential thermal resistance in graphene/hexagonal boron nitride heterostructures . Appl. Phys. Lett . 110 , 091907 ( 2017 ). doi: 10.1063/1.4977776 http://doi.org/10.1063/1.4977776 A wave-dominated heat transport mechanism for negative differential thermal resistance in graphene/hexagonal boron nitride heterostructures X.K. Chen , Z.X. Xie , W.X. Zhou et al ., Thermal rectification and negative differential thermal resistance behaviors in graphene/hexagonal boron nitride heterojunction . Carbon 100 , 492 - 500 ( 2016 ). doi: 10.1016/j.carbon.2016.01.045 http://doi.org/10.1016/j.carbon.2016.01.045 Thermal rectification and negative differential thermal resistance behaviors in graphene/hexagonal boron nitride heterojunction M. Pumera , Graphene-based nanomaterials for energy storage . Energy Environ. Sci . 4 , 668 - 674 ( 2011 ). doi: 10.1039/c0ee00295j http://doi.org/10.1039/c0ee00295j Graphene-based nanomaterials for energy storage S. Patchkovskii , J.S. Tse , S.N. Yurchenko et al ., Graphene nanostructures as tunable storage media for molecular hydrogen . Natl. Acad. Sci. USA . 102 , 10439 - 10444 ( 2005 ). doi: 10.1073/pnas.0501030102 http://doi.org/10.1073/pnas.0501030102 Graphene nanostructures as tunable storage media for molecular hydrogen D.W. Boukhvalov , M.I. Katsnelson , A.I. Lichtenstein , Hydrogen on graphene: electronic structure, total energy, structural distortions and magnetism from first-principles calculations . Phys. Rev. B 77 , 035427 ( 2008 ). doi: 10.1103/PhysRevB.77.035427 http://doi.org/10.1103/PhysRevB.77.035427 Hydrogen on graphene: electronic structure, total energy, structural distortions and magnetism from first-principles calculations D.C. Elias , R.P. Nair , T.M. Mohiuddin et al ., Control of grphene's properties by reversible hydrogenation: evidence for graphane . Science 323 , 610 - 613 ( 2009 ). doi: 10.1126/science.1167130 http://doi.org/10.1126/science.1167130 Control of grphene's properties by reversible hydrogenation: evidence for graphane R. Balog , B.J. Jorgensen , L. Nilsson et al ., Bandgap opening in graphene induced by patterned hydrogen adsorption . Nat. Mat . 9 , 315 - 319 ( 2010 ). doi: 10.1038/NMAT2710 http://doi.org/10.1038/NMAT2710 Bandgap opening in graphene induced by patterned hydrogen adsorption B.S. Pujari , S. Gusarov , M. Brett et al ., Single-side-hydrogenated graphene: Density functional theory predictions . Phys. Rev. B 84 , 041402 ( 2011 ). doi: 10.1103/PhysRevB.84.041402 http://doi.org/10.1103/PhysRevB.84.041402 Single-side-hydrogenated graphene: Density functional theory predictions S.S. Han , H. Jung , D.H. Jung et al ., Stability of hydrogenation states of graphene and conditions for hydrogen spillover . Phys. Rev. B 85 , 155408 ( 2012 ). doi: 10.1103/PhysRevB.85.155408 http://doi.org/10.1103/PhysRevB.85.155408 Stability of hydrogenation states of graphene and conditions for hydrogen spillover W. Zhou , J. Zhou , J. Shen et al ., First-principles study of high-capacity hydrogen storage on graphene with Li atoms . J. Phys. Chem. Solids . 73 , 245 - 251 ( 2012 ). doi: 10.1016/j.jpcs.2011.10.035 http://doi.org/10.1016/j.jpcs.2011.10.035 First-principles study of high-capacity hydrogen storage on graphene with Li atoms V. Tozzini , V. Pellegrini , Prospects for hydrogen storage in graphene . Phys. Chem. Chem. Phys . 15 , 80 - 89 ( 2013 ). doi: 10.1039/c2cp42538f http://doi.org/10.1039/c2cp42538f Prospects for hydrogen storage in graphene S. Gadipelli , Z. Guo , Graphene-based materials: synthesis and gas sorption, storage and separation . Prog. Mater. Sci . 69 , 1 - 60 ( 2015 ). doi: 10.1016/j.pmatsci.2014.10.004 http://doi.org/10.1016/j.pmatsci.2014.10.004 Graphene-based materials: synthesis and gas sorption, storage and separation H. Hu , J. Xin , H. Hu et al ., Metal-free graphene-based catalyste-insight into the catalytic activity: a short review . Appl. Catal. A. Gen . 492 , 1 - 9 ( 2015 ). doi: 10.1016/j.apcata.2014.11.041 http://doi.org/10.1016/j.apcata.2014.11.041 Metal-free graphene-based catalyste-insight into the catalytic activity: a short review M.L. Guillou , N. Toulhoat , Y. Pipon et al ., Deuterium migration in nuclear graphite: Consequences for the behavior of tritium in CO2-cooled reactors and for the decontamination of irradiated graphite waste . J. Nucl. Mater . 461 , 72 - 77 ( 2015 ). doi: 10.1016/j.jnucmat.2015.03.005 http://doi.org/10.1016/j.jnucmat.2015.03.005 Deuterium migration in nuclear graphite: Consequences for the behavior of tritium in CO2-cooled reactors and for the decontamination of irradiated graphite waste T.N. Hoai , K.H. Lam , N.T. Thanh et al ., Migration and desorption of hydrogen atom and molecule on/from graphene . Carbon 121 , 248 - 256 ( 2017 ). doi: 10.1016/j.carbon.2017.05.069 http://doi.org/10.1016/j.carbon.2017.05.069 Migration and desorption of hydrogen atom and molecule on/from graphene Y. Miura , H. Kasai , W. Dino et al ., First principles studies for the dissociative adsorption of H2 on graphene . J. Appl. Phys . 933 , 395 - 400 ( 2003 ). doi: 10.1063/1.1555701 http://doi.org/10.1063/1.1555701 First principles studies for the dissociative adsorption of H2 on graphene Z. Ao , S. Li , Graphene simulation; chap. Hydrogenation of graphene and hydrogen diffusion behavior on graphene/graphane interface . Rijeka, Croatia : InTech ; 2011 . Graphene simulation; chap. Hydrogenation of graphene and hydrogen diffusion behavior on graphene/graphane interface M. Terrones , A.R. Botello-Mendez , J. Campos-Delgado et al ., Graphene and graphite nanoribbons: morphology, properties, synthesis, defects and applications . Nano. Today . 5 , 351 - 372 ( 2010 ). doi: 10.1016/j.nantod.2010.06.010 http://doi.org/10.1016/j.nantod.2010.06.010 Graphene and graphite nanoribbons: morphology, properties, synthesis, defects and applications K.S. Novoselov , A.K. Geim , S.V. Morozov et al ., Two-dimensional gas of massless dirac fermions in graphene . Nature 438 , 197 - 200 ( 2005 ). doi: 10.1038/nature04233 http://doi.org/10.1038/nature04233 Two-dimensional gas of massless dirac fermions in graphene K. Nordlund , J. Keinonen , T. Mattila , Formation of ion irradiation induced small-scale defects on graphite surfaces . Phys. Rev. Lett . 77 , 699 - 702 ( 1996 ). doi: 10.1103/PhysRevLett.77.699 http://doi.org/10.1103/PhysRevLett.77.699 Formation of ion irradiation induced small-scale defects on graphite surfaces A. Hashimoto , K. Suenaga , A. Gloter et al ., Directevidence for atomic defects in graphene layers . Nature 430 , 870 - 873 ( 2004 ). doi: 10.1038/nature02817 http://doi.org/10.1038/nature02817 Directevidence for atomic defects in graphene layers P.O. Lehtinen , A.S. Foster , Y. Ma et al ., Irradiation-induced magnetism in graphite: a density functional study . Phys. Rev. Lett . 93 , 187202 ( 2004 ). doi: 10.1103/PhysRevLett.93.187202 http://doi.org/10.1103/PhysRevLett.93.187202 Irradiation-induced magnetism in graphite: a density functional study O.V. Yazyev , L. Helm , Defect-induced magnetism in graphene . Phys. Rev. B . 7 , 125408 ( 2007 ). doi: 10.1103/PhysRevB.75.125408 http://doi.org/10.1103/PhysRevB.75.125408 Defect-induced magnetism in graphene V.M. Pereira , D.S. Lopes , N.A. Castro , Modeling disorder in graphene . Phys. Rev. B . 77 , 115109 ( 2008 ). doi: 10.1103/PhysRevB.77.115109 http://doi.org/10.1103/PhysRevB.77.115109 Modeling disorder in graphene O.V. Yazyev , Magnetism in disordered graphene and irradiated graphite . Phys. Rev. Lett . 101 , 037203 ( 2008 ). doi: 10.1103/PhysRevLett.101.037203 http://doi.org/10.1103/PhysRevLett.101.037203 Magnetism in disordered graphene and irradiated graphite J.C. Meyer , C. Kisielowski , R. Erni et al ., Direct imaging of lattice atoms and topological defects in graphene membranes . Nano. Lett . 8 , 3582 - 3586 ( 2008 ). doi: 10.1021/nl801386m http://doi.org/10.1021/nl801386m Direct imaging of lattice atoms and topological defects in graphene membranes M.M. Ugeda , I. Brihuega , F. Guinea et al ., Missing atom as a source of carbon magnetism . Phys. Rev. Lett . 104 , 096804 ( 2010 ). doi: 10.1103/PhysRevLett.104.096804 http://doi.org/10.1103/PhysRevLett.104.096804 Missing atom as a source of carbon magnetism T. Kondo , Y. Honma , J. Oh et al ., Edge states propagating from a defect of graphite: scanning tunneling spectroscopy measurements . Phys. Rev. B . 82 , 153414 ( 2010 ). doi: 10.1103/PhysRevB.82.153414 http://doi.org/10.1103/PhysRevB.82.153414 Edge states propagating from a defect of graphite: scanning tunneling spectroscopy measurements B. Wen , M.S. Cao , M.M. Lu et al ., Reduced Graphene Oxides: Light-Weight and High-Efficiency Electromagnetic Interference Shielding at Elevated Temperatures . Adv. Mater . 26 , 3484 - 3489 ( 2014 ). doi: 10.1002/adma.201400108 http://doi.org/10.1002/adma.201400108 Reduced Graphene Oxides: Light-Weight and High-Efficiency Electromagnetic Interference Shielding at Elevated Temperatures M.S. Cao , X.X. Wang , W.Q. Cao et al ., Thermally driven transport and relaxation switching self-powered electromagnetic energy conversion . Small . 14 , 1800987 - 1800994 ( 2018 ). doi: 10.1002/smll.201800987 http://doi.org/10.1002/smll.201800987 Thermally driven transport and relaxation switching self-powered electromagnetic energy conversion W.Q. Cao , X.X. Wang , J. Yuan et al ., Temperature dependent microwave absorption of ultrathin graphene composites . J. Mater. Chem. C 3 , 10017 - 10022 ( 2015 ). doi: 10.1039/c5tc02185e http://doi.org/10.1039/c5tc02185e Temperature dependent microwave absorption of ultrathin graphene composites W.L. Song , M.S. Cao , Z.L. Hou et al ., High dielectric loss and its monotonic dependence of conducting-dominated multiwalled carbon nanotubes/silica nanocomposite on temperature ranging from 373 to 873 K in X-band . Appl. Phys. Lett.   94 , 233110 ( 2009 ). doi: 10.1063/1.3152764 http://doi.org/10.1063/1.3152764 High dielectric loss and its monotonic dependence of conducting-dominated multiwalled carbon nanotubes/silica nanocomposite on temperature ranging from 373 to 873 K in X-band Y.N. Tang , Z.Y. Liu , Z.G. Shen et al ., Adsorption sensitivity of metal atom decorated bilayer graphene toward toxic gas molecules (CO, NO, SO2 and HCN) . Sensor. Actuat. B: Chem . 238 , 182 - 195 ( 2017 ). doi: 10.1016/j.snb.2016.07.039 http://doi.org/10.1016/j.snb.2016.07.039 Adsorption sensitivity of metal atom decorated bilayer graphene toward toxic gas molecules (CO, NO, SO2 and HCN) Y.N. Tang , H.D. Chai , W.G. Chen et al ., Theoretical study on geometric, electronic and catalytic performances of Fe dopant pairs in graphene . Phys. Chem. Chem. Phys . 19 , 26369 - 26380 ( 2017 ). doi: 10.1039/c7cp05683d http://doi.org/10.1039/c7cp05683d Theoretical study on geometric, electronic and catalytic performances of Fe dopant pairs in graphene Y.N. Tang , W.G. Chen , Z.G. Shen et al ., Nitrogen coordinated silicon-doped graphene as a potential alternative metal-free catalyst for CO oxidation . Carbon 111 , 448 - 458 ( 2017 ). doi: 10.1016/j.carbon.2016.10.028 http://doi.org/10.1016/j.carbon.2016.10.028 Nitrogen coordinated silicon-doped graphene as a potential alternative metal-free catalyst for CO oxidation Y.N. Tang , H.D. Chai , H.W. Zhang et al ., Tuning the adsorption and interaction of CO and O-2 on graphene-like BC3-supported non-noble metal atoms . Phys. Chem. Chem. Phys . 20 , 14040 - 14052 ( 2018 ). doi: 10.1039/c8cp00772a http://doi.org/10.1039/c8cp00772a Tuning the adsorption and interaction of CO and O-2 on graphene-like BC3-supported non-noble metal atoms Y.N. Tang , Z.G. Shen , Y.Q. Ma et al , Divacancy-nitrogen/boron-codoped graphene as a metal-free catalyst for high-efficient CO oxidation . Mater. Chem. Phys . 207 , 11 - 22 ( 2018 ). doi: 10.1016/j.matchemphys.2017.12.048 http://doi.org/10.1016/j.matchemphys.2017.12.048 Divacancy-nitrogen/boron-codoped graphene as a metal-free catalyst for high-efficient CO oxidation L.H. Yao , W.Q. Cao , M.S. Cao et al ., Doping effect on the adsorption of Na atom onto graphenes . Current Applied Physics 16 , 574 - 580 ( 2016 ). doi: 10.1016/j.cap.2016.03.001 http://doi.org/10.1016/j.cap.2016.03.001 Doping effect on the adsorption of Na atom onto graphenes C. Marina , C. Simone , F.T. Gian et al ., Structure and stability of hydrogenated carbon atom vacancies in graphene . Carbon 77 , 165 - 174 ( 2014 ). doi: 10.1016/j.carbon.2014.05.018 http://doi.org/10.1016/j.carbon.2014.05.018 Structure and stability of hydrogenated carbon atom vacancies in graphene K. Yamashita , M. Saito , T. Oda , Atomic geometry and stability of mono-, di-, and trivacancies in graphene . Jpn. J. Appl. Phys . 45 , 6534 - 6536 ( 2006 ). doi: 10.1143/JJAP.45.6534 http://doi.org/10.1143/JJAP.45.6534 Atomic geometry and stability of mono-, di-, and trivacancies in graphene A.A. El-Barbary , R.H. Telling , C.P. Ewels et al ., Structure and energetics of the vacancy in graphite . Phys. Rev. B . 68 , 144107 ( 2003 ). doi: 10.1103/PhysRevB.68.144107 http://doi.org/10.1103/PhysRevB.68.144107 Structure and energetics of the vacancy in graphite A.V. Krasheninnikov , P.O. Lehtinen , A.S. Foster et al ., Bending the rules: contrasting vacancy energetics and migration in graphite and carbon nanotubes . Chem. Phys. Lett . 418 , 132 - 147 ( 2006 ). doi: 10.1016/j.cplett.2005.10.106 http://doi.org/10.1016/j.cplett.2005.10.106 Bending the rules: contrasting vacancy energetics and migration in graphite and carbon nanotubes D.Q. Xia , C.L. Ren , W. Zhang et al ., Theoretical study of the interaction between metallic fission products and defective graphite . Comput. Mater. Sci . 106 , 129 - 134 ( 2015 ). doi: 10.1016/j.commatsci.2015.04.029 http://doi.org/10.1016/j.commatsci.2015.04.029 Theoretical study of the interaction between metallic fission products and defective graphite Y. Lei , A.S. Stephen , W.G. Zhu et al ., Hydrogen-induced magnetization and tunable hydrogen storage in graphitic structures . Phys. Rev. B . 77 , 134114 ( 2008 ). doi: 10.1103/PhysRevB.77.134114 http://doi.org/10.1103/PhysRevB.77.134114 Hydrogen-induced magnetization and tunable hydrogen storage in graphitic structures Q.G. Jiang , Z.M. Ao , W.T. Zheng et al ., Enhanced hydrogen sensing properties of graphene by introducing a mono-atom-vacancy . Phys. Chem. Chem. Phys . 15 , 21016 - 21022 ( 2013 ). doi: 10.1039/c3cp52976b http://doi.org/10.1039/c3cp52976b Enhanced hydrogen sensing properties of graphene by introducing a mono-atom-vacancy G.K. Sunnardianto , I. Maruyama , K. Kusakabe , Dissociation-chemisorption pathways of H2 molecule on graphene activated by a hydrogenated mono-vacancy V11 . Adv. Sci. Eng. Med . 8 , 421 - 426 ( 2016 ). doi: 10.1166/asem.2016.1875 http://doi.org/10.1166/asem.2016.1875 Dissociation-chemisorption pathways of H2 molecule on graphene activated by a hydrogenated mono-vacancy V11 G.K. Sunnardianto , I. Maruyama , K. Kusakabe , Storing-hydrogen processes on graphene activated by atomic-vacancies . Int. J. Hydrogen Energy . 42 , 23691 - 23697 ( 2017 ). doi: 10.1016/j.ijhydene.2017.01.115 http://doi.org/10.1016/j.ijhydene.2017.01.115 Storing-hydrogen processes on graphene activated by atomic-vacancies P. Hohenberg , W. Kohn , Inhomogeneous electron gas . Phys. Rev. B . 136 , 864 ( 1964 ). doi: 10.1103/PhysRev.136.B864 http://doi.org/10.1103/PhysRev.136.B864 Inhomogeneous electron gas W. Kohn , L.J. Sham , Self-consistent equations including exchange and correlation effects . Phys. Rev. B . 140 , 1133 ( 1965 ). doi: 10.1103/PhysRev.140.A1133 http://doi.org/10.1103/PhysRev.140.A1133 Self-consistent equations including exchange and correlation effects G. Kresse , J. Furthmuller , Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set . Phys. Rev. B . 54 , 11169 - 11186 ( 1996 ). doi: 10.1103/PhysRevB.54.11169 http://doi.org/10.1103/PhysRevB.54.11169 Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set J.P. Perdew , J.A. Chevary , S.H. Vosko et al ., Atoms, Molecules, Solids, and surfaces-applications of the generalized gradient approximation for exchange and correlation . Phys. Rev. B . 46 , 6671 - 6687 ( 1992 ). doi: 10.1103/PhysRevB.46.6671 http://doi.org/10.1103/PhysRevB.46.6671 Atoms, Molecules, Solids, and surfaces-applications of the generalized gradient approximation for exchange and correlation P.E. Blochl , Projector Augmented-Wave Method Phys. Rev. B . 50 , 17953 - 17979 ( 1994 ). doi: 10.1103/PhysRevB.50.17953 http://doi.org/10.1103/PhysRevB.50.17953 Projector Augmented-Wave Method G. Henkelman , B.P. Uberuaga , H. Jonsson , A climbing image nudged elastic band method for finding saddle points and minimum energy paths . J. Chem. Phys . 113 , 9901 - 9904 ( 2000 ). doi: 10.1063/1.1329672 http://doi.org/10.1063/1.1329672 A climbing image nudged elastic band method for finding saddle points and minimum energy paths G. Henkelman , H. Jonsson , Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points . J. Chem. Phys . 113 , 9978 - 9985 ( 2000 ). doi: 10.1063/1.1323224 http://doi.org/10.1063/1.1323224 Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points C. Li , C. Fang , C. Yang , First-principle studies of radioactive fission productions Cs/Sr/Ag/I adsorption on chrome–molybdenum steel in Chinese 200 MW HTR-PM . Nucl. Sci. Tech . 28 , 79 - 88 ( 2017 ). doi: 10.1007/s41365-017-0241-8 http://doi.org/10.1007/s41365-017-0241-8 First-principle studies of radioactive fission productions Cs/Sr/Ag/I adsorption on chrome–molybdenum steel in Chinese 200 MW HTR-PM V. Morón , P. Gamallo , R. Sayós , DFT and kinetics study of O/O2 mixturesreacting over a graphite (0001) basal surface . Theor. Chem. Acc . 128 , 683 - 694 ( 2011 ). doi: 10.1007/s00214-010-0798-3 http://doi.org/10.1007/s00214-010-0798-3 DFT and kinetics study of O/O2 mixturesreacting over a graphite (0001) basal surface J. Fayos , Possible 3D carbon structures as progressive intermediates ingraphite to diamond phase transition . J. Solid State Chem . 148 , 278 - 285 ( 1999 ). doi: 10.1006/jssc.1999.8448 http://doi.org/10.1006/jssc.1999.8448 Possible 3D carbon structures as progressive intermediates ingraphite to diamond phase transition X.W. Sha , B. Jackson , First-principles study of the structural and energetic properties of H atoms on a graphite (0001) surface . Surf. Sci . 496 , 318 - 330 ( 2002 ). doi: 10.1016/S0039-6028(01)01602-8 http://doi.org/10.1016/S0039-6028(01)01602-8 First-principles study of the structural and energetic properties of H atoms on a graphite (0001) surface D.W. Boukhvalov , M.I. Katsnelson , A.I. Lichtenstein , Hydrogen on graphene: Electronic structure, total energy, structural distortions and magnetism from first-principles calculations . Phys. Rev. B . 77 , 035427 ( 2008 ). doi: 10.1103/PhysRevB.77.035427 http://doi.org/10.1103/PhysRevB.77.035427 Hydrogen on graphene: Electronic structure, total energy, structural distortions and magnetism from first-principles calculations Y. Miura , H. Kasai , W. Dino et al ., First principles studies for the disociative adsorption of H2 on graphene . J. Appl. Phys . 93 , 3395 - 3400 ( 2003 ). doi: 10.1063/1.1555701 http://doi.org/10.1063/1.1555701 First principles studies for the disociative adsorption of H2 on graphene P.O. Lethinen , A.S. Foster , Y. Ma et al ., Irradiation induced magnetism in graphene: a density functional study . Phys. Rev. Lett . 93 , 187202 ( 2004 ). doi: 10.1103/PhysRevLett.93.187202 http://doi.org/10.1103/PhysRevLett.93.187202 Irradiation induced magnetism in graphene: a density functional study O.V. Yazyev , L. Helm , Defect induced magnetism in graphene . Phys. Rev. B . 75 , 125408 ( 2007 ). doi: 10.1103/PhysRevB.75.125408 http://doi.org/10.1103/PhysRevB.75.125408 Defect induced magnetism in graphene M.W.C. Dharma-Wardana , M.Z. Zgierski , Magnetism and structure at vacant lattice sites in graphene . Phys. E . 41 , 80 - 83 ( 2008 ). doi: 10.1016/j.physe.2008.06.007 http://doi.org/10.1016/j.physe.2008.06.007 Magnetism and structure at vacant lattice sites in graphene X.Q. Dai , J.H. Zhao , M.H. Xie et al ., First-principle study on magnetism induced by Vacanies in graphene . Eur. Phys. J. B . 80 , 343 - 351 ( 2011 ). doi: 10.1140/epjb/e2011-10955-x http://doi.org/10.1140/epjb/e2011-10955-x First-principle study on magnetism induced by Vacanies in graphene F. Banhart , J. Kotakoski , A.V. Krasheninnikov , Structural defects in graphene . ACS. Nano . 5 , 26 - 41 ( 2011 ). doi: 10.1021/nn102598m http://doi.org/10.1021/nn102598m Structural defects in graphene 10.1007/s41365-019-0584-4 This work was supported by the National Natural Science Foundation of China (Nos. 51601212 and 11475082) and "Strategic Priority Research Program of Chinese Academy of Sciences" Thorium Molten Salts Reactor Fund. 2018-07-26 2018-09-19 2018-10-19 2019-03-25 2019-04-01 2021-04-10 © China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, ChineseNuclear Society and Springer Nature Singapore Pte Ltd. 2019 This is a post-peer-review, pre-copyedit version of an article published in Nuclear Science and Techniques. The final authenticated version is available online at: http://dx.doi.org/10.1007/s41365-019-0584-4 http://dx.doi.org/10.1007/s41365-019-0584-4 . 2019 Nuclear Science and Techniques 04 30