Liquid Metal Shell as an Effective Iron Oxide Modifier for Redox-Based Hydrogen Production at Intermediate Temperatures
Liquid Metal Shell as an Effective Iron Oxide Modifier for Redox-Based Hydrogen Production at Intermediate Temperatures
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DOI：
10.1021/acscatal.1c02102
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发表时间：
2021-08
期刊：
影响因子：
12.9
通讯作者：
Iwei Wang;Yunfei Gao;Xijun Wang;R. Cai;C. Chung;Sherafghan Iftikhar;Wei Wang;Fanxing Li
中科院分区：
文献类型：
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作者：
Iwei Wang;Yunfei Gao;Xijun Wang;R. Cai;C. Chung;Sherafghan Iftikhar;Wei Wang;Fanxing Li
该研究报告了熔融金属（铋、铟和锡）作为铁基氧化还原催化剂的有效改性剂，用于在中间温度（450-650 °C）下从低热值废气（例如，高炉煤气）。研究了铋助剂对铁氧化物表面和体相性质的影响。透射电子显微镜和能量色散谱（TEM-EDS）、低能离子散射（LEIS）、拉曼光谱和18 O2交换实验表明，铋改性剂形成了一个覆盖在铁（氧化物）上的覆盖层，与参比的La0.8Sr0.2FeO3和Ce0.9Gd0.1O2负载的铁氧化物相比，具有更好的抗结焦性能。Bi改性的样品还表现出改善的抗烧结性能和高氧化还原活性，在550 °C下的循环氧化还原反应下，与原始Fe 2 O3相比，氧容量增加了4倍（28.9 vs 6.4 wt %）。同时，少量的铋被掺杂到铁氧化物结构中，通过降低氧空位形成能（从3.1到2.1 eV）和空位迁移的能垒来有效地增强其氧化还原性能，如实验结果和密度泛函理论（DFT）计算所证实的。反应性测试表明，Bi改性氧化还原催化剂对转化低热值废气如高炉煤气具有高活性。我们的研究还表明，这种策略可以推广到低熔点金属，如Bi，In和Sn的氧化铁改性的化学循环过程。
This study reports molten metals (bismuth, indium, and tin) as effective modifiers for iron-based redox catalysts in the context of chemical looping-based hydrogen production at intermediate temperatures (450–650 °C) from low-calorific-value waste gas (e.g., blast furnace gas). The effects of the bismuth promoter on both the surface and bulk properties of iron oxides were studied in detail. Transmission electron microscopy and energy-dispersive spectroscopy (TEM-EDS), low-energy ion scattering (LEIS), Raman spectroscopy, and18O2exchange experiment revealed that the bismuth modifier forms an overlayer covering the bulk iron (oxides), leading to better anti-coking properties compared to reference La0.8Sr0.2FeO3- and Ce0.9Gd0.1O2-supported iron oxides. The Bi-modified sample also exhibited improved anti-sintering properties and high redox activity, resulting in a 4-fold increase in oxygen capacity compared to pristine Fe2O3(28.9 vs 6.4 wt %) under a cyclic redox reaction at 550 °C. Meanwhile, a small amount of bismuth is doped into the iron oxide structure to effectively enhance its redox properties by lowering the oxygen vacancy formation energy (from 3.1 to 2.1 eV) and the energy barrier for vacancy migration, as confirmed by the experimental results and density functional theory (DFT) calculations. Reactive testing indicates that Bi-modified redox catalysts are highly active to convert low-calorific-value waste gases such as blast furnace gas. Our study also indicates that this strategy can be generalized to low-melting-point metals such as Bi, In, and Sn for iron oxide modification in chemical looping processes.