Experimental and Theoretical Understanding of Nitrogen-Doping-Induced Strong Metal–Support Interactions in Pd/TiO2 Catalysts for Nitrobenzene Hydrogenation

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• 作者：Peirong Chen ; Abhishek Khetan ; Fengkai Yang ; Vadim Migunov ; Philipp Weide ; Sascha P. Stürmer ; Penghu Guo ; Kevin Kähler ; Wei Xia ; Joachim Mayer ; Heinz Pitsch ; Ulrich Simon ; Martin Muhler
• 刊名：ACS Catalysis
• 出版年：2017
• 出版时间：February 3, 2017
• 年：2017
• 卷：7
• 期：2
• 页码：1197-1206
• 全文大小：678K
• ISSN：2155-5435

文摘

By doping the TiO₂ support with nitrogen, strong metal–support interactions (SMSI) in Pd/TiO₂ catalysts can be tailored to obtain high-performance supported Pd nanoparticles (NPs) in nitrobenzene (NB) hydrogenation catalysis. According to the comparative studies by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance CO FTIR (CO–DRIFTS), N-doping induced a structural promoting effect, which is beneficial for the dispersion of Pd species on TiO₂. High-angle annular dark-field scanning transmission electron microscopy study of Pd on N-doped TiO₂ confirmed a predominant presence of sub-2 nm Pd NPs, which are stable under the applied hydrogenation conditions. XPS and CO–DRIFTS revealed the formation of strongly coupled Pd–N species in Pd/TiO₂ with N-doped TiO₂ as support. Density functional theory (DFT) calculations over model systems with Pd_n (n = 1, 5, or 10) clusters deposited on TiO₂(101) surface were performed to verify and supplement the experimental observations. In hydrogenation catalysis using NB as a model molecule, Pd NPs on N-doped TiO₂ outperformed those on N-free TiO₂ in terms of both catalytic activity and stability, which can be attributed to the presence of highly dispersed Pd NPs providing more active sites, and to the formation of Pd–N species favoring the dissociative adsorption of the reactant NB and the easier desorption of the product aniline.