Recently, the professor Zeng Jie of the University of Science and Technology of China established the Pt3Co octapod alloy nanocrystals and used its tip effect to achieve efficient CO2 catalytic hydrogenation. The results of this study were published in the August 8th German Journal of Applied Chemistry (Angew. Chem. Int. Ed. 2016, 55, 9548-9552) and were selected as cover and hot topics. The common first author of the dissertation was Munir Ullah Khan, a Pakistani student, Wang Liangbing, a doctoral student, and Liu Xi, a doctoral student.
As an extremely stable molecule, CO2 molecules are often difficult to be activated. Therefore, how to effectively activate CO2 is the key to improving the catalytic activity of its hydrogenation reaction. In general, the electronic structure of the catalyst surface is a major factor affecting the performance of the catalyst. Theoretical studies have shown that electrons tend to concentrate in sharp-edged regions such as vertices and edges, ie, tip effects. In addition, the difference in electronegativity in the alloy also leads to electron transfer, which changes the electronic structure of the catalyst. This provides researchers with ideas for regulating the electronic structure of metal nanocrystals.
Based on this, the researchers designed and constructed Pt3Co octapodal alloy nanocrystals, which exhibited excellent catalytic activity in the catalytic hydrogenation of CO2. Compared with Pt3Co cubes, Pt octapods and Pt cubic nanocrystals, the conversion frequency of Pt3Co octapodal alloy nanocrystals catalyzing the hydrogenation of CO2 to methanol is 2.2, 6.1 and 6.6 times that of Pt3Co. The first-principles study shows that the sharp tip structure of Pt3Co octapodal alloy nanocrystals leads to electron enrichment at the tip due to the tip effect. In addition, in Pt3Co alloys, since the electronegativity of Pt is higher than that of Co, the electrons on the Co atom will transfer to the Pt atom, so that the Pt atoms at the tip will be enriched in electrons. This phenomenon is confirmed in the X-ray photoelectron spectroscopy test. . Subsequently, based on in-situ infrared reflectance absorption spectra, the researchers observed that CO2 was activated to CO2 delta-radicals by catalytic action of Pt3Co metal nanocrystals, confirming that the enrichment of electrons at the tip of the Pt atom favors CO2 activation. This research provides a new research idea for improving the catalytic performance of nano-metal nanocrystals by regulating their surface states.
The study was funded by the Ministry of Science and Youth's "973" program and the National Natural Science Foundation.
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