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Mercury is a toxic heavy metal, and mercury emitted in various forms in production and life poses a certain degree of threat to ecology and human health. Therefore, it is of great importance to find highly effective mercury adsorbents. Based on the first-principles calculation method of density functional theory, the adsorption and oxidation mechanism of mercury on Ti2NO2（MXene） and Ti2NO2 with an oxygen vacancy(Ov-Ti2NO2) defect was studied. The calculation results show that the adsorption of Hg0 on the surface of Ti2NO2 is physical adsorption and the adsorption on the surface of Ov-Ti2NO2 is chemical adsorption. The presence of oxygen vacancies on the surface of Ti2NO2 can improve the interaction between HgO and Ov-Ti2NO2, thereby increasing the adsorption energy by 116 kJ/mol. The reaction barrier of Hg0 oxidation to HgO on the surface of Ov-Ti2NO2 is 92.55 kJ/mol, which is smaller than the energy barrier of its oxidation reaction on the surface of Ti2NO2（101.42 kJ/mol), which is more conducive to the oxidation of Hg0. In addition, the energy required for the desorption of HgO on Ov-Ti2NO2 surface is 226.18 kJ/mol, which is much higher than that of 110.49 kJ/mol on Ti2NO2 surface, indicating that the Ov-Ti2NO2 has better control ability of product HgO than Ti2NO2, which can inhibit secondary pollution caused by HgO desorption. [ABSTRACT FROM AUTHOR]

Mo2 FeB2 is a good boron based cermet material with high temperature resistance, wear resistance and high strength. It has broad application in the field of mould. The structural stability, elastic properties, hardness and electronic structure of Mo2 FeB2 with Nb alloying were investigated by using first-principles calculations. The calculated cohesive energy and formation enthalpy showed that Nb prefers to occupy the Fe site of Mo2 FeB2, and the Nb at Fe site of Mo2 FeB2 possesses better mechanical properties compared with that at Mo site. Moreover, the calculated results showed that Nb doping could increase the shear modulus, Young’s modulus, bulk modulus and hardness, but slightly decrease the ductility. The suitable doping concentration should be 2.5 at. %. The calculated electronic structure indicated that the increase of mechanical properties is attributed to the formation of Nb-B covalent bonds. [ABSTRACT FROM AUTHOR]

As the most important component of greenhouse gases, the change of carbon dioxide content will directly affect global climate change. Selective capture of CO2 in post combustion gases is of great significance to mitigate environmental problems caused by excessive CO2 concentration. In this paper, the first principle calculation method was used to study the selective adsorption performance of V2CO2 MXene material for CO2. Firstly, the structures and properties of V2CO2 MXene materials with different functional groups were studied. It was found that V2CO2 had good stability. Later, the adsorption behavior of V2CO2 on CO2 was studied. The results showed that when CO2 was horizontally adsorbed, V2CO2 had a strong adsorption capacity for CO2 gas molecules, which met the ideal value(-0.42 eV-0.82 eV) of CO2 adsorption on the surface of high-performance adsorbent, and could be suitable for detecting/capturing CO2 gas molecules. In addition, the adsorption behavior of N2 on V2CO2 under the same conditions was further studied. The results showed that the adsorption of V2CO2 on N2 was very weak. Therefore, V2CO2 can selectively adsorb CO2 from CO2/N2 mixture, which is expected to be a candidate material for selective adsorption of CO2 in post combustion gases. [ABSTRACT FROM AUTHOR]

In this paper, the stabilities of carbon nanocones (CNC), B and N-doped carbon nanocones (B-CNC and N-CNC) are studied by first principle calculation combined with ab initio molecular dynamics. The results show that CNC, B-CNC and N-CNC can exist stably. On this basis, the adsorption behaviors of Na atoms on CNC, B-CNC and N-CNC are studied respectively. The results show that: 1) the adsorption of Na atom at the center of CNC five membered carbon ring is the strongest, and the adsorption energy is-2.52 eV. The energy gap (Eg) of CNC is 1.96 eV. 2) After B and N doping CNC, the conductivities of B-CNC and N-CNC are significantly enhanced. 3) Compared with CNC, the adsorption of Na atoms on B-CNC is enhanced, while the adsorption on N-CNC is significantly weakened. This shows that B-CNC is expected to be used as the anode material of Na ion battery. The research results of this paper provide theoretical guidance for the research of Na ion battery with CNC as anode material. [ABSTRACT FROM AUTHOR]

In this paper, first-principles calculations combined with ab initio molecular dynamics methods were used to study the stability of carbon nanocones (CNC), B- and N-doped carbon nanocones (B-CNC and N-CNC). Both B-CNC and N-CNC can exist stably. On this basis, the adsorption behaviors of Na atoms on CNC, B-CNC and N-CNC are studied respectively. The results show that: 1) Na atoms in the center of CNC five-membered carbon ring The adsorption at the top position is the strongest with an adsorption energy of -2.52 eV. The energy gap (Eg) of CNC is 1.96 eV. 2) After B and N doping CNC, the conductivity of both B-CNC and N-CNC is significantly enhanced. 3 ) Compared with CNC, the adsorption of Na atoms on B-CNC is enhanced, while the adsorption on N-CNC is significantly weakened. This indicates that B-CNC is promising as an anode material for Na-ion batteries. It provides theoretical guidance for the research of Na-ion batteries with anode materials. [ABSTRACT FROM AUTHOR]

As a neurotoxic and corrosive gas pollutant, hydrogen sulfide poses a serious threat to human health and limits the development of industry. In this paper, the adsorption behavior of H2S gas molecules on the original pentagonal graphene, nonmetal doped graphene and metal doped pentagonal graphene was studied by first principles calculation. The adsorption configuration, adsorption energy and charge transfer between H2S and graphene were calculated in detail. The results show that: 1) there is only weak physical adsorption be tween the original pentagonal graphene and non-metallic elements doped graphene and H2S gas molecules, while cannot be directly used to adsorb H2S gas. 2) The adsorption of H2S gas on pentagonal graphene doped with Co,Ni,Cu and Ti was significantly enhanced. When the metal atom doped at the sp²C position, the adsorption effect of the doped pentagonal graphene on H2S was better, and the adsorption in this condition belongs to chemical adsorption. 3) Co, Ni, Cu and Ti doped pentagonal graphene can be used as H2S gas sensing/ trapping materials. Among them, Cu-doped pentagonal graphene has the best adsorption effect on H2S gas. It is hoped that the research result in this paper can provide theoretical guidance for the design and development of hydrogen sulfide gas sensing/ trapping materials based on pentagonal graphene [ABSTRACT FROM AUTHOR]