Synthesis, characterization and application of platinum based bi-metallic catalysts for direct glucose alkaline fuel cell

Abstract

In the context of development of direct glucose fuel cell (DGFC), low metal loading (ca. 15 wt.%) bi-metallic platinum–bismuth (PtBi/C) and platinum–gold (PtAu/C) catalysts are synthesized by immobilizing metal sols on carbon substrate (Vulcan XC 72R). Physical characterization of electro-catalysts, studied using TEM, SEM, EDX and XRD, reveals the formation of nano-sized metal particles on carbon substrate. The cyclic voltammetry and chronoamperometry of the prepared catalysts point out that PtAu/C is more active and stable than PtBi/C and commercial PtRu/C towards glucose electro-oxidation in alkaline medium. The catalysts are tested as anode in batch DGFC using activated charcoal as cathode in different glucose and electrolyte (KOH solution) concentrations at ambient temperature (30 °C). Open-circuit voltage of ∼0.9 V is obtained for PtAu/C and commercial PtRu/C and 0.8 V for PtBi/C anode in 0.2 M glucose and in 1 M KOH. However, the peak power density per unit metal loading or specific peak power density obtained is 1.6 mW cm −2 mg −1 for PtAu/C followed by PtBi/C (1.25 mW cm −2 mg −1) and commercial PtRu/C (1.13 mW cm −2 mg −1). For PtBi/C and PtRu/C, the cell performance increases up to 0.2 M glucose concentration and then decreases. However, for PtAu/C catalyst the cell performance increases up to 0.3 M glucose concentration and then decreases. A prominent transition zone is observed in which current density sharply decreases with the decrease in voltage (increase in overpotential) for PtBi/C and PtRu/C at 0.3 M glucose concentration, which is not observed in the case of PtAu/C. The transition zone for PtAu/C is insignificant and at higher glucose concentration (0.4 M) pointing out that PtAu/C is much stable catalyst than PtBi/C and commercial PtRu/C.