A Sulfite/Air Fuel Cell with Alkali and Sulfuric Acid Byproducts: Bifunctional Electrocatalyst for Sulfite Oxidation and ORR Activity

This work attempted to synthesize bifunctional Pd-Pt bimetallic catalysts for a sulfite/air fuel cell via a simple ethylene glycol reduction method. As-prepared Pd-Pt bimetallic catalysts were characterized by transmission electron microscope, X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The diameter of the Pt-Pd bimetals was ∼3–6 nm. The mechanisms of sulfite oxidation and oxygen reduction were investigated. The cell performance was determined to be largely dependent on the sulfite oxidation activity of the catalyst. S(Ⅳ) → S(Ⅵ) is the principal sulfite oxidation reaction for Pd/C, PtPd7.33/C, and PtPd2.75/C, whereas S(Ⅳ) → S(Ⅴ) is the principal reaction for Pt/C, Pt2.18Pd/C, and PtPd1.22/C. PtPd2.75/C is considered a promising bifunctional catalyst for the sulfite/air fuel cell, which exhibits excellent electrochemical activity and long-term stability.