从密度泛函理论计算中H2，O2，H2O，CO2，CO，CH4和C2Hx在金属Mo2C（001）和Mo / C终止的Mo2C（101）上的活化机理,Applied Catalysis A: General

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从密度泛函理论计算中H2，O2，H2O，CO2，CO，CH4和C2Hx在金属Mo2C（001）和Mo / C终止的Mo2C（101）上的活化机理
Applied Catalysis A: General ( IF 4.7 ) Pub Date : 2016-07-18 13:44:38
Yun Shi, Yong Yang, Yong-Wang Li, Haijun Jiao

基于自旋极化的周期性密度泛函理论，包括最新的色散校正（PBE-D3），H ₂，O ₂，H ₂ O，CO ₂，CO，CH ₄和C ₂ H _x的解离吸附机理计算出六角形的Mo ₂ C表面。在我们的研究中，我们使用金属Mo ₂ C（001）表面以及Mo / C = 1/1比率的Mo ₂ C（101）表面。发现这些小分子的解离吸附是放热的，并且具有低的势垒。并且Mo ₂ C（001）表面具有比Mo ₂强得多的解离吸附C（101）表面。与Mo ₂ C（001）表面相反，OH + H和O + 2H可以在Mo ₂ C（101）表面上形成平衡。对于Mo ₂ C（001）表面上的C ₂ H _x解离吸附，CH键解离在动力学上比CC键解离更有利，并且最佳C ₂ H ₆解离路径遵循C ₂ H ₆ →CH的顺序。₃ CH ₂ + H→C ₂ H ₄ + 2H→CH ₂ CH + 3H→C ₂ H ₂ + 4H→C ₂ H + 5H→C ₂+6小时。由于非常强的离解吸附能，使用H ₂ O可以很容易地氧化两个表面。并且可以预期到高的氧气覆盖率。Mo ₂ C（001）表面比Mo ₂ C（101）表面可以吸收更多的表面O原子。这些表面也可以通过使用CH ₄渗碳，尽管程度不大。与CO ₂ + 4H共吸附的表面；与CO ₂（CO ₂ + H→HCOO或COOH）和CO（CO + H→HCO或COH）的氢化相比，CO ₂解离（CO ₂ →CO + O→C + 2O）更有利。注意到CO ₂加氢成CH ₄在Mo ₂ C（001）表面上形成的可能性不大，而通过2O和2OH预覆盖的表面可以降低Mo ₂ C（101）表面上表面C氢化的有效势垒。

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Activation mechanisms of H2, O2, H2O, CO2, CO, CH4 and C2Hx on metallic Mo2C(001) as well as Mo/C terminated Mo2C(101) from density functional theory computations

On the basis of spin-polarized periodic density functional theory including the latest dispersion correction (PBE-D3), the mechanisms of H₂, O₂, H₂O, CO₂, CO, CH₄ and C₂H_x dissociative adsorption on the hexagonal Mo₂C surface have been computed. In our study we used the metallic Mo₂C(001) surface as well as the Mo₂C(101) surface with Mo/C=1/1 ratio. It is found that the dissociative adsorptions of these small molecules are exothermic and have low barriers; and the Mo₂C(001) surface has much stronger dissociative adsorption than the Mo₂C(101) surface. In contrast to the Mo₂C(001) surface, OH+H and O+2H can form equilibrium on Mo₂C(101) surface. For C₂H_x dissociative adsorption on the Mo₂C(001) surface, CH bond dissociation is kinetically much more favorable than the CC bond dissociation, and the optimum C₂H₆ dissociation route follows the order of C₂H₆ →CH₃CH₂ +H→C₂H₄ +2H→CH₂CH+3H→C₂H₂ +4H→C₂H+5H→C₂ +6H. Due to the very strong dissociative adsorption energies, both surfaces can be oxidized easily by using H₂O; and high oxygen coverage can be expected. The Mo₂C(001) surface can uptake more surface O atoms than the Mo₂C(101) surface. These surfaces can also be carburized by using CH₄, albeit in less extent. On the surface with co-adsorbed CO₂ +4H; CO₂ dissociation (CO₂ →CO+O→C+2O) is more favorable than the hydrogenation of CO₂ (CO₂ +H→HCOO or COOH) and CO (CO+H→HCO or COH). It is noted that CO₂ hydrogenation towards CH₄ formation is unlikely on the Mo₂C(001) surface, while the effective barrier of surface C hydrogenation on the Mo₂C(101) surface can be reduced by 2O and 2OH pre-covered surfaces.

更新日期：2016-07-19

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