Insights into the catalytic behavior of LaMnO3 perovskite for Hg0 oxidation by HCl
Insights into the catalytic behavior of LaMnO3 perovskite for Hg0 oxidation by HCl
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DOI：
10.1016/j.jhazmat.2019.121156
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发表时间：
2020-02-05
影响因子：
13.6
通讯作者：
Zhang, Zhen
中科院分区：
文献类型：
--
作者：
Wang, Zhen;Liu, Jing;Zhang, Zhen
具有钙钛矿结构的LaMnO 3基催化剂由于其优异的催化活性、高的热稳定性和独特的氧化还原行为，在Hg-0氧化反应中受到越来越多的关注。了解LaMnO 3对Hg-0的氧化行为将拓宽LaMnO 3基钙钛矿材料在Hg-0去除领域的应用。采用密度泛函理论（DFT）方法研究了HCl氧化Hg-0在LaMnO 3表面的催化机理.结果表明，Mn封端的LaMnO 3（010）表面比La封端的LaMnO 3（010）表面具有更高的活性和稳定性。Hg-0和HgCl_2在LaMnO_3（010）表面发生化学吸附。HgCl在LaMnO_3（010）表面发生分子吸附，并作为HgO氧化反应的中间体。HCl在LaMnO_3（010）表面发生解离吸附，生成表面活性氯配合物。Langmuir-Hinshelwood机理，其中化学吸附的Hg-0与解离吸附的HCl反应，负责HCl在LaMnO 3（010）上氧化Hg-0。Hg-0在表面上的催化氧化包含四个步骤：Hg-0 -> Hg（ads）-> HgCl（ads）-> HgCl 2（ads）-> HgCl 2，第二步（Hg（ads）-> HgCl（ads））由于其相对较大的能垒（0.74 eV）而成为速率控制步骤。
LaMnO3-based catalysts with perovskite structure have gained increasing interest for Hg-0 oxidation owing to their excellent catalytic activity, high thermal stability and unique redox behavior. Understanding the Hg-0 oxidation behavior on LaMnO3 will broaden the application of LaMnO3-based perovskites in Hg-0 removal field. Density functional theory (DFT) calculations were conducted to examine the catalytic mechanism of Hg-0 oxidation by HCl on LaMnO3 surface. The results indicate that Mn-terminated LaMnO3(010) surface is more active and stable than La-terminated surface. Hg-0 and HgCl2 are chemisorbed on LaMnO3(010) surface. HgCl can be molecularly chemisorbed on LaMnO3(010) and serve as an intermediate in Hg-0 oxidation reaction. HCl dis-sociatively adsorbs on LaMnO3(010) and generates surface active chlorine complexes. Langmuir-Hinshelwood mechanism, where the chemisorbed Hg-0 reacts with the dissociatively adsorbed HCl, is responsible for Hg-0 oxidation by HCl on LaMnO3(010). Catalytic Hg-0 oxidation over the surface contains four-steps: Hg-0 -> Hg(ads) -> HgCl(ads) -> HgCl2(ads) -> HgCl2, and the second step (Hg(ads) -> HgCl(ads)) is the rate-determining step because of its relatively larger energy barrier (0.74 eV).