Enhanced CO Oxidation Rates at the Interface of Mesoporous Oxides and Pt Nanoparticles
Enhanced CO Oxidation Rates at the Interface of Mesoporous Oxides and Pt Nanoparticles
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DOI：
10.1021/ja4088743
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发表时间：
2013-11-06
影响因子：
15
通讯作者：
Somorjai, Gabor A.
中科院分区：
文献类型：
--
作者：
An, Kwangjin;Alayoglu, Selim;Somorjai, Gabor A.
在氧化物负载的过渡金属催化剂中，金属与载体的相互作用被证明对催化性能有非常有利的影响。本文合成了介孔Co3O4、NiO、MnO2、Fe2O3和CeO2，并将其用于CO氧化反应，比较了负载2.5 nm铂纳米颗粒前后的催化活性。纯介孔氧化物的周转频率(TOF)为0.0002-0.015 S(-1)，而介孔二氧化硅对CO氧化反应无催化活性。当铂纳米粒子被负载到氧化物上时，铂/金属氧化物体系的TOF(0.1500 S(-1))比纯氧化物或二氧化硅负载的铂纳米粒子的TOF大一个数量级。改变反应气体中CO和O-2的比例进一步影响了不同的铂/氧化物体系的催化活性，这为观察到的载体效应的机理提供了深入的认识。利用近边X射线吸收精细结构(NEXAFS)和常压X射线光电子能谱(APXPS)在催化相关反应条件下的原位表征表明，氧化物载体的氧化状态与氧化物-金属界面的催化活性之间存在很强的相关性。通过催化活性测定和原位X射线光谱分析，确定了CoO、Mn3O4和CeO2为催化剂与铂纳米颗粒界面的活性表面相。
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 O-2 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.