Decoding structure-selectivity interplay in Pd-Ag nanocatalysts for butadiene semi-hydrogenation

Precisely controlling product selectivity within complex reaction networks remains a central challenge in heterogeneous catalysis. This difficulty largely arises from the strong coupling among catalyst geometry, electronic structure, and the spatial distribution of active sites, making it difficult to independently identify how each factor governs reaction pathways and product formation. Using the selective semi-hydrogenation of 1,3-butadiene as a model reaction, researchers systematically investigated how particle size and alloy composition cooperatively regulate catalytic activity and product selectivity over Pd–Ag bimetallic nanocatalysts, with the aim of establishing the intrinsic relationship between catalyst structure and selectivity.

By tuning the reduction temperature and Ag/Pd ratio, a series of monometallic Pd and bimetallic Pd–Ag nanocatalysts with controlled particle sizes and electronic structures were constructed, enabling the geometric and electronic effects to be effectively disentangled. Through a combination of kinetic analysis, chemisorption measurements, and density functional theory calculations, quantitative correlations between catalyst structure and product distribution were established. The results identify the Pd–Ag ensemble size and the average Pd valence state as two key descriptors governing reaction selectivity. Larger Pd–Ag ensembles with relatively low-valent Pd weaken the adsorption of 1-butene and facilitate its desorption, thereby suppressing its further hydrogenation to butane and isomerization to 2-butenes and promoting selective 1-butene formation.

The optimized Pd–Ag catalyst delivered a 1-butene selectivity of up to 66% at nearly complete 1,3-butadiene conversion while maintaining a total butene selectivity of over 98%, together with excellent stability during extended operation. Kinetic and chemisorption studies showed that larger Pd–Ag ensembles adsorb 1,3-butadiene more strongly while allowing the newly formed 1-butene to desorb more readily. Density functional theory calculations further revealed that, on large Pd–Ag ensembles, the pathway toward 1-butene is kinetically more favorable than the competing pathways leading to the thermodynamically more stable 2-butenes and further hydrogenation products. These results clarify how geometric and electronic effects act cooperatively to reshape the reaction-energy landscape and ultimately determine product selectivity.

Overall, this study establishes a clear structure–selectivity framework by systematically disentangling the geometric and electronic contributions in Pd–Ag bimetallic nanocatalysts. Beyond providing mechanistic insight into selective 1,3-butadiene hydrogenation, the work offers a general strategy for the rational design of bimetallic catalysts, in which active-site ensemble size, electronic state, and adsorption energetics are jointly tailored to direct complex reaction networks toward desired high-value products. The results were published in Chinese Journal of Catalysis (DOI: 10.1016/S1872-2067(26)65078-4)

About the Journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top six journals in Applied Chemistry with a current SCI impact factor of 17.2. The Editors-in-Chief are Profs. Can Li and Tao Zhang.

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