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arXiv 1902.04788cond-mat.mtrl-sci
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Ni1-xFexOOH合金的应变控制水氧化催化效率

Strain Controlling Catalytic Efficiency of Water Oxidation for Ni1-xFexOOH alloy

Ester Korkus Hamal, Maytal Caspary Toroker

摘要:

催化剂表面可能由于施加负载或与具有大晶格失配的基底接合而暴露于应变。为了测试应变对催化效率的影响,我们使用密度泛函理论+U(DFT+U)来模拟Ni 1-xFexOOH合金的膨胀和收缩表面上的水氧化,Ni 1-xFexOOH合金是用于水裂解的最知名的催化剂之一。我们发现,少量的铁含量具有与施加压缩应变类似的效果。由于活性中心Fe 4+的高氧化态,Fe-O键比纯FeOOH中的短,这有利于从离域在Fe和Ni原子上的状态提取电子。在33%的Fe含量下,效率甚至更好,因为Fe 3+处于活性位点并且在反应期间可以容易地改变氧化态。然而,在较高的铁百分比下效率下降,因为表面不稳定并且可能形成FeOOH聚集体。我们发现,最好的性能是在33%的铁含量和5%的膨胀。因此,除了改变铁含量外,应变还可以用作改善水裂解催化的控制柄。

英文摘要:

A catalyst surface may be exposed to strain due to application of load or interfacing with a substrate with large lattice mismatch. In order to test the effect of strain on catalytic efficiency, we use Density Functional Theory +U (DFT+U) to model water oxidation on expanded and contracted surfaces of the Ni1-xFexOOH alloy, one of the best known catalysts for water splitting. We find that a low amount of iron content has a similar effect as of applying compressive strain. Due to high oxidation state of Fe4+ at the active site, the Fe-O bond is shorter than in pure FeOOH, which is beneficial for extracting electrons from states delocalized on Fe and Ni atoms. At 33% of Fe content the efficiency is even better since Fe3+ is at the active site and can easily change oxidation state during the reaction. However, the efficiency drops at higher iron percentages since the surface is unstable and may form FeOOH aggregates. We find that the best performance is obtained at 33% iron content and 5% expansion. Therefore, in addition to changing iron content, strain can also be used as a control handle for improving water splitting catalysis.

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