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Pd/TiO Nanocatalyst with Strong Metal–Support Interaction for Highly Efficient Durable Heterogeneous Hydrogenation

Imran, M., Yousaf, Ammar B., Zhou, Xiao, Jiang, Yi-Fan, Yuan, Cheng-Zong, Zeb, Akif, Jiang, Nan, Xu, An-Wu
The Journal of Physical Chemistry C 2017 v.121 no.2 pp. 1162-1170
X-ray photoelectron spectroscopy, activation energy, adsorption, catalysts, catalytic activity, dissociation, hydrogen, hydrogenation, nanoparticles, p-nitrophenol, styrene, synergism, titanium, transmission electron microscopy
Developing heterogeneous catalysts that promote activation of hydrogen and adsorption of reactants on the surface is crucial to improve the activity of hydrogenation reactions. Herein, we present the use of highly reduced TiO support for loading noble metal nanoparticles, which provides a synergistic effect on boosting catalytic activity. The low-temperature polymorph of titanium monoxide is used as support and promoter, which contains vacancies in both the Ti and O sublattices with ordered distribution. The lattice vacancies increase the donor density and enhance the adsorption of substrate and hydrogen and subsequently lower the activation energy required for the hydrogen dissociation. Moreover, the existence of strong metal–support interactions in Pd/TiO ascertained from HRTEM and XPS analysis is responsible for both the strong binding of Pd nanoparticles and improved electronic conductivity, resulting in enhanced catalytic performance. The as-synthesized Pd/TiO catalyst has been evaluated for the hydrogenation of styrene and 4-nitrophenol (4-NP) and shows excellent performance. The rate constant for 4-NP reduction over Pd/TiO is 0.05 s–¹, which is higher than the previously reported data; moreover, the catalyst shows good stability up to 10 successive cycles. Hydrogenation of styrene is conducted at ambient conditions using Pd/TiO as catalyst, which exhibits remarkably high turnover frequency (TOF) of 4838 h–¹. The catalyst can be recovered and recycled several times without a marked loss of activity. The results show that our Pd/TiO catalyst is one of the highest activity among reported heterogeneous hydrogenation catalysts. The obtained Pd/TiO catalyst may hold great potential in catalysis for organic transformations and other reactions.