Plasma-engineered CeO2-p/CNTs with high ORR activity for direct borohydride fuel cells

Abstract

Direct borohydride fuel cells (DBFCs) are hindered by the sluggish cathode oxygen reduction reaction (ORR) and the high cost of Pt/C catalysts. Herein, CeO₂-p/CNTs catalysts were fabricated via dielectric barrier discharge (DBD) plasma treatment of CeO₂/CNTs composites. Plasma treatment optimizes the catalyst structure by achieving uniformly dispersed ∼5 nm CeO₂ nanoparticles, increased oxygen vacancies, strengthened CeO₂–CNTs interfacial interactions, and a tailored microporous–mesoporous structure (4–6 nm). Benefiting from the reversible Ce³⁺ (42.08%)/Ce⁴⁺ redox cycle, the catalyst exhibits outstanding ORR performance (E_1/2 = 0.868 V vs. RHE, Tafel slope = 299 mV dec⁻¹) in 0.1 M KOH. When applied to DBFC cathodes, it delivers a peak power density of 199.34 mW cm⁻² at 290 mA cm⁻² and maintains stable operation for 80 h at 40 mA cm⁻², outperforming most reported non-noble metal catalysts. This work provides a facile, low-cost strategy for high-performance ORR catalysts, thereby advancing the industrialization of DBFCs.