汞在Ti_(2)NO_(2) MXene表面吸附氧化的第一性原理计算

First-principles calculation of adsorption and oxidation of mercury on the Ti_(2)NO_(2) MXene surface

汞是一种有毒的重金属,在生产生活中以各种形式排放的汞对生态及人类健康都存在一定程度的威胁.因此,寻找高效的汞吸附剂具有十分重要的意义.本文基于密度泛函理论的第一性原理计算方法,研究了汞在Ti_(2)NO_(2)(MXene)和具有一个氧空位缺陷的Ti_(2)NO_(2)(Ov-Ti_(2)NO_(2))上的吸附和氧化机理.计算结果表明Hg0在Ti_(2)NO_(2)表面的吸附为物理吸附,在Ov-Ti_(2)NO_(2)表面为化学吸附. Ti_(2)NO_(2)表面氧空位的存在可以改善HgO与Ov-Ti_(2)NO_(2)之间的相互作用,从而使吸附能提高116 kJ/mol. Hg0在Ov-Ti_(2)NO_(2)表面氧化为HgO的反应能垒为92.55 kJ/mol,小于其在Ti_(2)NO_(2)表面氧化反应的能垒(101.42 kJ/mol),更有利于Hg0的氧化.此外,产物HgO在Ov-Ti_(2)NO_(2)表面脱附需要226.18 kJ/mol能量,远高于在Ti_(2)NO_(2)表面脱附所的110.49 kJ/mol,说明Ov-Ti_(2)NO_(2)对产物HgO的集中控制能力优于Ti_(2)NO_(2),从而更能抑制HgO脱附造成二次污染.

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 Ti_(2)NO_(2)(MXene)and Ti_(2)NO_(2) with an oxygen vacancy(Ov-Ti_2NO_(2))defect was studied.The calculation results show that the adsorption of Hg~0 on the surface of Ti_(2)NO_(2) is physical adsorption and the adsorption on the surface of Ov-Ti_2NO_(2)is chemical adsorption.The presence of oxygen vacancies on the surface of Ti_2NO_(2)can improve the interaction between HgO and Ov-Ti_(2)NO_(2),thereby increasing the adsorption energy by 116 kJ/mol.The reaction barrier of Hg~(0)oxidation to HgO on the surface of Ov-Ti_(2)NO_(2) is 92.55 kJ/mol,which is smaller than the energy barrier of its oxidation reaction on the surface of Ti_(2)NO_(2)(101.42 kJ/mol),which is more conducive to the oxidation of Hg~0.In addition,the energy required for the desorption of HgO on Ov-Ti_(2)NO_(2) surface is 226.18 kJ/mol,which is much higher than that of 110.49 kJ/mol on Ti_(2)NO_(2) surface,indicating that the Ov-Ti_(2)NO_(2) has better control ability of product HgO than Ti_(2)NO_(2),which can inhibit secondary pollution caused by HgO desorption.