水滑石负载AuCu合金催化水煤气变换反应:催化性能与结构组成

Water Gas Shift Reaction Catalyzed by AuCu Alloy Nanoparticles Supported on Layered Double Hydroxides: Catalytic Performance and Structural Composition

以ZnAl水滑石(ZnAl-LDHs)为载体,合成了负载Au和AuCu合金的水滑石(Au/LDHs和AuCu/LDHs)用于催化水煤气变换反应(WGSR)。利用X射线粉末衍射(XRD)、高分辨率透射电镜(HRTEM)及扫描透射电子显微镜(STEM)表征了负载型催化剂的结构与组成。探讨了不同的Au和Cu物质的量之比(nAu∶nCu)对AuCu/LDHs催化WGSR性能的影响并与Au/LDHs的活性进行了对比。结果表明,负载Au纳米颗粒可明显的提升LDHs催化WGSR的活性,而负载AuCu合金后其活性又进一步的提升。当nAu∶nCu=2∶1时具有最佳的催化效率:活性为207.1μmol·gcat^-1·s^-1,TOF值为1.79s^-1,活化能为31.1kJ·mol^-1。通过分析对比不同样品的物理化学性质参数,探讨了不同的nAu∶nCu对Au的粒径、分散度、覆盖度及反应活性的影响。此外,X射线光电子能谱(XPS)分析表明,加入第二金属Cu形成合金后增大了Au^δ+组分在体系中的含量(nAu∶nCu=2∶1时含量最高),这可能是负载体系催化WGSR具有高活性的原因。

Au nanoparticles supported on layered double hydroxides (Au/LDHs) and AuCu alloy nanoparticles supported on layered double hydroxides (AuCu/LDHs) based on ZnAl layered double hydroxides (ZnAl-LDHs) were synthesized and used for catalyzing water gas shift reaction (WGSR). The structure and composition of Au/LDHs and AuCu/LDHs was characterized and confirmed by using X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning and transmission electron microscope (STEM). The effect of different molar ratios of Au and Cu (nAu∶nCu) for AuCu/LDHs onto the catalytic performance of WGSR was investigated and compared with the activity from Au/LDHs. It indicates that Au/LDHs has obviously higher activity compared to plain LDHs, while, AuCu alloy supporting can further largely enhance the catalytic activity for WGSR. Au2Cu1/LDHs (nAu∶nCu=2∶1) exhibited the best catalytic efficiency:activity was 207.1 μmol·gcat^-1·s^-1, TOF was 1.79 s^-1, and activity energy was 31.1 kJ·mol^-1. The effect of nAu∶nCu onto the Au particle size, Au dispersity, coverage degree of Au, and catalytic activity was discussed based on the comparison of physicochemical properties for different catalysts. The active species of Au/LDHs and AuCu/LDHs with different nAu∶nCu were analyzed and compared by X-ray photoelectron spectrometry (XPS). It was found that the introduction of the secondary element increased the percentage of Au^δ+(Au2Cu1/LDHs had the highest Au^δ+ content), which maybe resulted in the enhancement of WGSR activity.