Cobalt-Modified Palladium Bimetallic Catalyst: A Multifunctional Electrocatalyst with Enhanced Efficiency and Stability toward the Oxidation of Ethanol and Formate in Alkaline Medium

In recent years, there has been an ever-increasing demand for liquid-fueled energy carriers, including direct ethanol fuel cells and direct formate fuel cells. Current research on liquid fuel cells is focused on the exploration of new, durable, and highly efficient non-platinum based electrocatalysts with long-term stability. In this research, bimetallic palladium–cobalt (Pd–Co) nanoalloys were investigated as bifunctional anode catalysts with enhanced efficiency and stability toward the direct electrooxidation of ethanol and formate in alkaline medium. X-ray diffraction, transmission electron microscopy–energy-dispersive spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy were employed for the in-depth characterization of the nanocatalysts synthesized by a modified polyol reduction process in triethylene glycol medium. Electrochemical analysis via cyclic voltammetry and chronoamperometry revealed improved electrocatalytic activity and excellent stability in alkaline medium toward the anodic oxidation of liquid fuels: ethanol (ethanol oxidation reaction, EOR) and formate (formate oxidation reaction, FOR). Excellent mass activity values as high as 3.7 A mg–1 and 3.2 A mg–1 were observed for the as-made Pd2.3Co/C and PdCo/C electrocatalyst samples, respectively, during EOR. In addition, enhanced FOR activity and high durability were observed for the Pd2.3Co/C catalyst compared to that of Pd/C prepared in a similar manner. The superior electrochemical activities for the prepared bimetallic catalysts compared to monometallic Pd/C is related to the reduced poisoning on the catalyst surface, induced by the synergistic effect and an altered Pd electronic structure by the incorporation of Co.