Optimizing the RuCo Ratio for More Efficient and Durable Oxygen Reduction in Acidic Media

Abstract

The development of Pt-free catalysts for the oxygen reduction reaction (ORR) is a great issue for meeting the cost challenges of proton exchange membrane fuel cells (PEMFCs) in commercial applications. In this work, a series of RuCo/C catalysts were synthesized by NaBH4 reduction method under the premise that the total metal mass percentage was 20%. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) confirmed the formation of single-phase nanoparticles with an average size of 33 nm. Cyclic voltammograms (CV) and linear sweep voltammograms (LSV) tests indicated that RuCo (2:1)/C catalyst had the optimal ORR properties. Additionally, the RuCo (2:1)/C catalyst remarkably sustained 98.1% of its activity even after 3 000 cycles, surpassing the performance of Pt/C (84.8%). Analysis of the elemental state of the catalyst surface after cycling using X-ray photoelectron spectroscopy (XPS) revealed that the Ru⁰ percentage of RuCo (2: 1)/C decreased by 2.2% (from 66.3% to 64.1%), while the Pt⁰ percentage of Pt/C decreased by 7.1% (from 53.3% to 46.2%). It is suggested that the synergy between Ru and Co holds the potential to pave the way for future low-cost and highly stable ORR catalysts, offering significant promise in the context of PEMFCs.

Keywords

electrocatalysis / oxygen reduction / durability / RuCo/C / fuel cell

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