Synthesis And Catalytic Studies Of Palladium-silver And Platinum-tin Nanocrystals

Owing to its excellent catalytic property, Pd and Pt are important catalysts in industrial production. To solve the scarce reserve problem of Pd and Pt, we developed colloidal method to prepare Ag Pd and Pt-Sn nanocrystals(NCs) and explored the catalytic properties for hydrogenation reactions and electro-oxidation of formic acid, respectively. The outstanding catalytic performance of them makes the efficient use of Pd and Pt to be possible. The catalytic capabilities of bimetallic nanocrystals are closely related to their size, morphology, composition, and other structure factors. Therefore, fabricating high efficient nanocatalysts dependents on the deep understanding of the reaction and well-controlled nano-synthesis technology. By adjusting the composition of Ag Pd and Pt-Sn nanocrystals, the catalytic activity and selectivity are significantly enhanced, based on which the structure-catalytic property relationship is intensively unveiled by systematical characterizations.We fabricated an excellent hydrodechlorination catalyst-Pd Ag alloy NCs. Pd Ag alloy NCs with tunable compositions and narrow size distributions were prepared in octadecylamine. The NCs growth process was investigated by time-dependent characterizations. In the hydrodechlorination of 4-chlorophenol, the NCs showed a pronounced composition-dependent catalytic activity. The different catalytic functions of Pd and Ag in the hydrodechlorination reaction were clarified, which further renders us to develop better catalyst for the environment protection.Pt-Sn NCs with tunable compositions and narrow size distributions were synthesized and used as catalysts for regioselective hydrogenation of α,β-unsaturated aldehydes. X-ray characterizations revealed their structures evolve from Sn O2-x-patched Pt Sn alloys to Sn O2-x-patched Pt clusters when more tin was incorporated. In the hydrogenation of cinnamaldehyde, the selectivity to unsaturated alcohol increased with the increasement of tin content, while the catalytic activity followed a volcano shape. It was further demonstrated that Pt sites were responsible for hydrogen dissociation, whereas density functional theory calculations indicated that oxygen vacancy(Ovac) sites, which was provided by Sn O2-x, drastically enhanced the adsorption of carbonyl group. This work represents a correlation of “composition–structure–property”, and may pave new avenue for advanced nanocatalysts in biomass conversion.We explored low temperature, one-step synthesis of Pt Sn intermetallic compounds. Concave and multi-defects cubic Pt3 Sn intermetallic compounds were fabricated, and the formation mechanism of these two different morphologies was studied. As-synthesized Pt3 Sn intermetallic compounds with different morphologies displayed different electro-catalytic activities in the electro-oxidation of formic acid, and the multi-defects cubic Pt3 Sn showed the best activity and poisoning-resistant property. This work improves the scarce studies in the controlled-morphology fabrication of intermetallic compounds and provides a material base for the application of intermetallic compounds.