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The Tunable and Highly Selective Reduction Products on Ag@Cu Bimetallic Catalysts Toward CO2 Electrochemical Reduction Reaction

Chang, Zhiyuan, Huo, Shengjuan, Zhang, Wei, Fang, Jianhui, Wang, Hailiang
The Journal of Physical Chemistry C 2017 v.121 no.21 pp. 11368-11379
carbon dioxide, carbon monoxide, catalysts, copper, electrochemistry, ethylene glycol, geometry, hydrocarbons, models, nanoparticles, physical chemistry, polyols, polyvinylpyrrolidone, reducing agents, silver, synergism
Bimetallic electrocatalysts can improve the activity and selectivity over their monometallic counterparts by tuning the structure, morphology, and composition. However, there scarcely was a systematic model to understand the structural effect relationship on CO₂ electrochemical reduction reaction, especially for a product tuning process by introduction of a second metal to grow into outer layers. Herein, we report a structure-controlled model of the growth process of Ag@Cu bimetallic nanoparticles that are fabricated by a polyol method, that is, reducing mixtures of Ag⁺ and Cu²⁺ (excess amount) in ethylene glycol (reducing agent) in the presence of polyvinylpyrrolidone. Structural characterizations reveal that a series of Ag@Cu NPs are tuned from the Ag core, Cu modified Ag, to the Cu outer shell by controlling the heating time (0–25 min). Moreover, highly selective catalysts with the tuning reduction products from carbon monoxide to hydrocarbons can be realized. Different from the “dilution” effects between Ag and Cu, the volcanic curve for carbon monoxide production is detected for the introduction of Cu and the peak point is the Ag@Cu-7 electrocatalyst (heating time is 7 min). Similarly, interestingly, when the Cu cladding layer continuously grows, the hydrocarbons are not a simple proportional addition and optimized at Ag@Cu-20 (heating time is 20 min). The geometric effects dominantly account for the synergistic effect of CO product and control the surface activity to hydrocarbons. This study serves as a good starting point to tune the energetics of the intermediate binding to achieve even higher selectivity and activity for core–shell structured catalysts.