α-Fe_(2)O_(3)(001)及其掺杂表面吸附As_(2)O_(3)机制的密度泛函理论

Density functional theory of the adsorption mechanism of As_(2)O_(3) on α-Fe_(2)O_(3)(001) and its doped surface

为提高催化剂抗砷能力,采用密度泛函理论(DFT)方法研究As_(2)O_(3)在α-Fe_(2)O_(3)(001)表面的吸附行为以及掺杂Mo、Mn、Ni对α-Fe_(2)O_(3)(001)表面As_(2)O_(3)吸附行为的影响。建立As_(2)O_(3)在α-Fe_(2)O_(3)(001)表面吸附模型和Mo、Mn、Ni掺杂的吸附模型,计算As_(2)O_(3)在催化剂表面的吸附能,分析成键态密度以及掺杂前后的As_(2)O_(3)在α-Fe_(2)O_(3)(001)表面的电荷布局。结果表明:这4种体系均发生电子转移,Mo掺杂活化了As_(2)O_(3)分子,使得As_(2)O_(3)倾向于吸附在Mo活性位点上,保护了Fe活性位点,增强α-Fe_(2)O_(3)抗砷中毒能力;Mn、Ni掺杂后As_(2)O_(3)反应活性低于掺杂前,抑制了As与掺杂剂的吸附,导致Fe位点更易中毒,不利于之后的NH 3-SCR反应。

In this paper,density functional theory(DFT)method is used to study the adsorption behavior of As_(2)O_(3) on α-Fe_(2)O_(3)(001) surface and the influence of doping Mo,Mn and Ni on the adsorption behavior of As_(2)O_(3) on α-Fe_(2)O_(3)(001) surface.The adsorption model of As_(2)O_(3) on the surface ofα-Fe_(2)O_(3)(001) and the adsorption model of Mo,Mn and Ni doping were established.The adsorption energy of As_(2)O_(3) on the catalyst surface was calculated.The density of bonding states and the charge layout of As_(2)O_(3) on the surface ofα-Fe_(2)O_(3)(001)before and after doping are analyzed.Electron transfer occurs in the four systems.Mo doping activates As_(2)O_(3)molecules,makes As_(2)O_(3) tend to be adsorbed on Mo active sites,protects Fe active sites,and enhances the anti-arsenic poisoning ability ofα-Fe_(2)O_(3).After Mn and Ni doping,the reaction activity of As_(2)O_(3)is lower than before,which inhibits the adsorption of As_(2)O_(3)and increases the poisoning effect of the catalyst,which is not conducive to the subsequent NH 3-SCR reaction.