Composition engineering of carbon nanotubes supported PtxRhRu ultrafine nanocatalysts for ethanol electro-oxidation: Elucidating the role of trimetallic sites

The practice of direct ethanol fuel cells (DEFCs) is hindered by insufficient activity of anode Pt-based catalyst for ethanol oxidation reaction (EOR), while alloying Rh and Ru to Pt is hopeful to solve the problem by simultaneously enhancing C-C cleavage and decreasing poisoning; and Ru owning better stability and activity than usually doped Sn in alkaline electrolyte. Nevertheless, Pt-Rh-Ru catalysts were rarely reported. In this work, to avoid random trials, the composition engineering strategy was applied to design PtxRhRu catalysts. The optimal x range was predicted by DFT. Then, carbon nanotubes supported PtxRhRu ultrafine nanoparticles (PtxRhRu/CNTs) were synthesized and characterized. The synthetic mechanism was also studied. EOR tests show that, in line with the forecast, Pt4RhRu/CNTs (similar to 1.9 nm) exhibit the highest activity (5.85 mA.cm(-2)), 6.97 times of commercial Pt/C, and higher than most reports. The selectivity, stability and durability are also excellent. DFT analysis reveals the role of Pt-Rh-Ru site for the first time, that the optimal route on PtxRhRu is changed. New route clearly enhances complete ethanol oxidation and reduces poisoning. Bifunctional mechanism on Pt-Rh-Ru site was also confirmed. This study may provide new perspective for material design; the products are also promotive for DEFCs into practice.

Automated summary

This study demonstrates the use of alloying Rh and Ru to Pt catalysts to improve the activity and stability of direct ethanol fuel cells (DEFCs). By applying the composition engineering strategy, PtxRhRu catalysts were designed and synthesized. The results showed improved activity and stability, highlighting the importance of material design in practical DEFC applications.