J Am Chem Soc. 2013 Nov 6;135(44):16689-96. doi: 10.1021/ja4088743.
The interaction of the metal and support in oxide-supported transition-metal catalysts has been proven to have extremely favorable effects on catalytic performance. Herein, mesoporous Co3O4, NiO, MnO2, Fe2O3, and CeO2 were synthesized and utilized in CO oxidation reactions to compare the catalytic activities before and after loading of 2.5 nm Pt nanoparticles. Turnover frequencies (TOFs) of pure mesoporous oxides were 0.0002–0.015 s(–1), while mesoporous silica was catalytically inactive in CO oxidation. When Pt nanoparticles were loaded onto the oxides, the TOFs of the Pt/metal oxide systems (0.1–500 s(–1)) were orders of magnitude greater than those of the pure oxides or the silica-supported Pt nanoparticles. The catalytic activities of various Pt/oxide systems were further influenced by varying the ratio of CO and O2 in the reactant gas feed, which provided insight into the mechanism of the observed support effect. In situ characterization using near-edge X-ray absorption fine structure (NEXAFS) and ambient-pressure X-ray photoelectron spectroscopy (APXPS) under catalytically relevant reaction conditions demonstrated a strong correlation between the oxidation state of the oxide support and the catalytic activity at the oxide–metal interface. Through catalytic activity measurements and in situ X-ray spectroscopic probes, CoO, Mn3O4, and CeO2 have been identified as the active surface phases of the oxide at the interface with Pt nanoparticles.
氧化物负载的过渡金属催化剂中金属与载体的相互作用已被证明对催化性能具有极其有利的影响。在此，合成了介孔 Co3O4、NiO、MnO2、Fe2O3 和 CeO2，并将其用于 CO 氧化反应中，以比较负载 2.5nmPt 纳米粒子前后的催化活性。纯介孔氧化物的转化频率（TOF）为 0.0002–0.015 s(–1)，而介孔二氧化硅在 CO 氧化中没有催化活性。当 Pt 纳米粒子负载到氧化物上时，Pt/金属氧化物体系（0.1–500 s(–1)）的 TOF 比纯氧化物或负载在二氧化硅上的 Pt 纳米粒子的 TOF 高几个数量级。各种 Pt/氧化物体系的催化活性进一步受到反应物气体进料中 CO 和 O2 比例的影响，这为观察到的载体效应的机制提供了深入的了解。在催化相关反应条件下使用近边 X 射线吸收精细结构（NEXAFS）和常压 X 射线光电子能谱（APXPS）进行的原位表征表明，氧化物载体的氧化态与氧化物-金属界面处的催化活性之间存在很强的相关性。通过催化活性测量和原位 X 射线光谱探针，确定 CoO、Mn3O4 和 CeO2 是与 Pt 纳米粒子界面处的氧化物的活性表面相。
