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[Display omitted] • Ir – TiO 2 interaction was dependent on Ir sizes and crystal plane of TiO 2. • Both activity and selectivity of the catalysts increased as the Ir size grew from single atom to nanoparticle. • End-on C O adsorption of crotonaldehyde was favored at the Ir-TiO x interface for Ir nanoparticles. • Crotonaldehyde adsorption geometry depends on H coverage on the catalyst surface. For the supported catalysts for the selective hydrogenation of α, β - unsaturated aldehyde with H 2 , tailoring of metal - support interfacial effect to improve reaction performance is a significant but challenging subject. In this work, we regulated both the size regimes of the Ir deposits (single atom, nanocluster and nanoparticle) and the crystal plane of anatase TiO 2 (TiO 2 (1 0 1), TiO 2 (1 0 0) and TiO 2 (0 0 1)) so as to alter the Ir-TiO x interfacial properties, in order to unravel reaction mechanism of selective hydrogenation of crotonaldehyde over the Ir/TiO 2 catalysts. Both the activity and selectivity to crotyl alcohol increased as the Ir size grew from single atom to nanoparticle, ascribed to high Ir0 content, high concentration of surface defects and prominent H-spillover effect on the Ir nanoparticles. Moreover, the in situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations demonstrated that an end-on C O adsorption mode for crotonaldehyde molecule was favored at the Ir-TiO x interface particularly at high H coverage, which thus facilitated the hydrogenation of C O bond to form crotyl alcohol. Moreover, the highest reactivity of the Ir nanoparticles was evidenced by the lowest reaction barrier. These results explicitly demonstrate that larger metal nanoparticles and adsorption geometry of the reactant at the metal - support interface are vital for improved catalytic performance, which would shed light on the ingenious catalyst design. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catalytic performance of Ir/TiO 2 catalysts depended on the crystal plane of TiO 2. • Ir/TiO 2 -{1 0 1} catalyst gave 4-fold higher activity than that of Ir/TiO 2 -{0 0 1} catalyst. • The defects sites of TiO x support were responsible for the formation of crotyl alcohol. • Ir-TiO x interfacial sites may account for the formation of 1-butanol. Supported Ir/TiO 2 catalysts with the anatase TiO 2 nanocrystals exposing {1 0 1}, {1 0 0} and {0 0 1} planes were tested for selective hydrogenation of crotonaldehyde. The Ir/TiO 2 -{1 0 1} catalyst dominantly exposing {1 0 1} plane gave a initial reaction rate of 166.1 μmol g Ir -1 s−1 at 80 °C and a turnover frequency of crotyl alcohol formation of 0.022 s−1, which is 5 and 7 times respectively higher than those obtained on the Ir/TiO 2 -{0 0 1} catalyst dominantly exposing {0 0 1} plane even though they have similar Ir particle sizes (ca. 1.3 nm). The reaction behaviors were related to the surface oxygen vacancy, which served as surface acid sites and provide adsorption sites for C O bond in the CRAL molecule. Therefore, the higher concentration of oxygen vacancy in the Ir/TiO 2 -{1 0 1} accounted for the improved performance compared to the Ir/TiO 2 -{0 0 1}. However, strong adsorption of crotonaldehyde and/or products on the catalyst surface, as well as the CO poisoning via decarbonylation of crotonaldehyde, were the main reasons for the catalyst deactivation. [ABSTRACT FROM AUTHOR]

The catalytic performance of Ir/TiO2-FeOx, an Ir/TiO2 catalyst modified with FeOx, was investigated for the hydrogenation of o-chloronitrobenzene, FeOx was found to promote both the activity and selectivity significantly. The initial reaction rate of Ir/TiO2-FeOx(10) nanocomposite catalyst was four times as high as that of Ir/TiO2 catalyst. Especially, the accumulation of intermediates was prohibited and finally 100% selectivity to o-chloroaniline was obtained at 100% conversion. Herein, we mainly discussed the promoting effect of FeOx with using the results of powder X-ray diffraction, transmission electron microscopy, element analysis mapping, hydrogen-temperature programmed reduction, hydrogen-temperature programmed desorption, diffuse reflectance infrared fourier transform spectra and X-ray photoelectron spectroscopy analysis. The FeOx was highly dispersed and a portion of FeO species existed in the Ir/TiO2-FeOx nanocomposite catalyst. Moreover, the FeOx was certified to have a strong interaction with Ir species, which should contribute to the excellent performance of the Ir/TiO2-FeOx nanocomposite catalyst. [ABSTRACT FROM AUTHOR]