Design of compressively strained PtRu alloy as anode for high-performance DMFCs

Abstract

Direct methanol fuel cells (DMFCs) are considered favorable for portable devices due to their high energy density and the widespread availability of methanol fuel. However, the commercialization of DMFCs has been severely limited by the sluggish reaction kinetics and poor stability of the anode. In this study, compressively strained PtRu alloy nanoparticles were deposited on a nanoporous thin film (NPTF) using a differential normal pulse voltammetry technique. The resulting compressive structure is confirmed through geometrical phase analysis, revealing high-level compressive strains of about −5%. Owing to the improved specific activity and high specific surface area, the compressively strained PtRu alloy nanoparticles exhibit outstanding Pt mass activities for methanol oxidation reaction. NPTF-Pt₂Ru₁ with a Pt/Ru molar ratio of 2/1 exhibits the highest Pt mass activity (1.64 A mg_Pt⁻¹), approximately 4 times higher than that of commercial PtRu/C. When applied in membrane electrode assembly, this film anode in DMFCs further exhibits mass activity enhancement owing to the structural advantages such as weakened methanol cross-over. With a loading of 0.21 mg_Pt cm⁻², the maximum power density at 80 °C reaches 117 mW cm⁻², and the power efficiency of Pt is about 12 times higher than that of commercial PtRu/C (2 mg_Pt cm⁻², 92 mW cm⁻²). Therefore, the methodology outlined in this study demonstrates a novel and effective means of synthesizing high-performance anode catalysts for DMFCs.