El Barraj Ali, Chatelain Baptiste, Barth Clemens
Aix-Marseille Univ, CNRS, CINaM, Marseille, France.
J Phys Condens Matter. 2021 Oct 26;34(1). doi: 10.1088/1361-648X/ac26f9.
The inverse catalyst 'cerium oxide (ceria) on copper' has attracted much interest in recent time because of its promising catalytic activity in the water-gas-shift reaction and the hydrogenation of CO. For such reactions it is important to study the redox behaviour of this system, in particular with respect to the reduction by H. Here, we investigate the high-temperature Ooxidation and Hreduction of ceria nanoparticles (NPs) and a Cu(111) support by low energy electron diffraction (LEED), scanning tunnelling microscopy (STM), non-contact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). After oxidation at 550 °C, the ceria NPs and the Cu(111) support are fully oxidized, with the copper oxide exhibiting a new oxide structure as verified by LEED and STM. We show that a high Hdosage in the kilo Langmuir range is needed to entirely reduce the copper support at 550 °C. A work function (WF) difference of △≈ -0.6 eV between the ceria NPs and the metallic Cu(111) support is measured, with the Cu(111) surface showing no signatures of separated and confined surface regions composed by an alloy of Cu and Ce. After oxidation, the WF difference is close to zero (△≈ -0.1…0 eV), which probably is due to a WF change of both, ceria and copper.
近年来，“铜上的氧化铈（二氧化铈）”这种逆催化剂因其在水煤气变换反应和一氧化碳加氢反应中展现出的催化活性而备受关注。对于此类反应，研究该体系的氧化还原行为十分重要，尤其是关于氢还原方面。在此，我们通过低能电子衍射（LEED）、扫描隧道显微镜（STM）、非接触原子力显微镜（nc-AFM）和开尔文探针力显微镜（KPFM）研究了二氧化铈纳米颗粒（NPs）和Cu(111)载体的高温氧化和氢还原过程。在550°C氧化后，二氧化铈纳米颗粒和Cu(111)载体被完全氧化，通过LEED和STM验证，氧化铜呈现出一种新的氧化物结构。我们发现，在550°C下完全还原铜载体需要千朗缪尔范围内的高氢剂量。测量得到二氧化铈纳米颗粒与金属Cu(111)载体之间的功函数（WF）差值约为△≈ -0.6 eV，Cu(111)表面未显示出由铜和铈合金组成的分离且受限表面区域的特征。氧化后，WF差值接近零（△≈ -0.1…0 eV），这可能是由于二氧化铈和铜的WF均发生了变化。
