Selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts: Unraveling the metal-support interface related reaction mechanism

• Published in: Journal of catalysis Vol. 425; pp. 57 - 69
• Main Authors: Jia, Aiping, Zhang, Wei, Peng, Hantao, Zhang, Yunshang, Song, Tongyang, Li, Lei, Ye, Yanwen, Wang, Yu, Luo, Mengfei, Chen, De-Li, Huang, Weixin, Lu, Ji-Qing
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2023
• Subjects: adsorption; alcohols; aldehydes; catalysts; catalytic activity; Density functional theory; Fourier transform infrared spectroscopy; geometry; H-spillover effect; Hydrogenation; Ir/TiO2; Nanocluster; Nanoparticle; nanoparticles; reaction mechanisms; Single atom; α, β - unsaturated aldehyde; Nanocluster; Ir/TiO2; Nanoparticle; H-spillover effect; Single atom; Density functional theory; α, β - unsaturated aldehyde; Hydrogenation
• ISSN: 0021-9517
• DOI: 10.1016/j.jcat.2023.05.029

[Display omitted] •Ir – TiO2 interaction was dependent on Ir sizes and crystal plane of TiO2.•Both activity and selectivity of the catalysts increased as the Ir size grew from single atom to nanoparticle.•End-on CO adsorption of crotonaldehyde was favored at the Ir-TiOx 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 H2, 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 TiO2 (TiO2(101), TiO2(100) and TiO2(001)) so as to alter the Ir-TiOx interfacial properties, in order to unravel reaction mechanism of selective hydrogenation of crotonaldehyde over the Ir/TiO2 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 CO adsorption mode for crotonaldehyde molecule was favored at the Ir-TiOx interface particularly at high H coverage, which thus facilitated the hydrogenation of CO 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.