Characterization and Electrooxidation Activity of Ternary Metal Catalysts Containing Au, Ga, and Ir for Enhanced Direct Borohydride Fuel Cells

Abstract

Carbon nanotube (CNT)-supported catalysts were synthesized by the sodium borohydride (NaBH4) reduction method and characterized by X-ray diffraction, transmission electron microscopy, inductively coupled plasma-mass spectrometry, and X-ray photoelectron spectroscopy analyses. The catalytic activities of the catalysts were examined by cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and linear sweep voltammetry electrochemical analyses for direct borohydride fuel cells (DBFCs) in NaBH4 solution. The characterization analyses revealed the structure, particle size, and metal ratios of CNT-supported metals. The NaBH4 electrooxidation results indicate that the 3% AuGaIr/CNT catalyst had a specific activity of 5.65 (1529.98 mA mg(-1) Au) mA cm(-2) and higher catalytic activity than the other catalysts. Furthermore, the electrochemical surface area (ECSA) values were obtained by calculating the reduction peak of the metal oxide in the NaOH solution by CV analysis. The ECSA value (128.57 m(2) g(-1)) of 3% AuGaIr/CNT catalyst was much higher than the other catalysts. The 3% AuGaIr/CNT catalyst had faster electron transfer rate with low (961.8 omega) charge transfer resistance (R-ct) and also high stability compared to the other catalysts. The study presents an up-and-coming new type of anode catalyst for DBFC applications. [GRAPHICS] .