氧缺陷影响铁基载氧体氧化-还原行为的分子动力学模拟

Molecular dynamics simulation of the influence of oxygen deficiency on the oxidation-reduction behavior of iron-based oxygen carriers

铁基载氧体是化学链燃烧中最受青睐的金属载氧体。构造了氧化铁载氧体的S完整表面和S^(1*)、S^(2*)、S^(3*)三种代表性缺陷表面,基于密度泛函理论(density function theory,DFT),首先计算分析了氧缺陷对CO在α-Fe_(2)O_(3)表面上吸附反应的影响,即对比了完整和缺陷α-Fe_(2)O_(3)(001)表面上CO的吸附和生成物CO_(2)的解离;其次将反应后的载氧体构型表面进行O_(2)吸附反应的模拟;继而对此载氧体一个循环及过程中铁基载氧体表面的积碳趋势进行了模拟分析。通过吸附能、反应能垒和反应能等参数的比较,结果显示,在铁基载氧体表面还原、积碳、氧化反应中,S^(1*)类氧缺陷具有更好的反应活性和抗积碳性能,具有良好的循环反应性能。该模拟研究为缺陷类型铁基载氧体的制备及其反应条件的确定提供指导。

The iron-based oxygen carrier is the most popular metal oxygen carrier in chemical looping combustion.The complete surface(shown as S)of the iron-based oxide carrier and the other three representative defect surfaces(S^(1*),S^(2*),S^(3*))were constructed.Based on the density functional theory(DFT)calculations,the effect of oxygen defect on CO adsorption reaction onα-Fe_(2)O_(3)surface was calculated and analyzed.That is,the adsorption of CO,the dissociation of CO_(2) on intact and defectiveα-Fe_(2)O_(3)(001)surfaces were compared.Then O_(2) adsorption reaction on the oxygen carrier structure surface after the reaction was simulated.In addition,the carbon accumulation trend of a cycle of the oxygen carrier and the surface of the iron-based oxygen carrier was simulated and analyzed.By comparing the adsorption energy,oxygen vacancy formation energy,reaction energy barrier,reaction energy and other parameters,the preliminary conclusions showed that in the reduction,carbon deposition and oxidation reactions,S^(1*)oxygen defects had better reactivity and resistance to carbon deposition,and had good cyclic reaction performance.The results provide directional guidance for the preparation and construction of iron-based oxygen carriers.