Electrocatalytic evaluation of sorbitol oxidation as a promising fuel in energy conversion using Au/C, Pd/C and Au–Pd/C synthesized through ionic liquids

Abstract

Abstract Sorbitol is a potentially cheap fuel that can be easily produced from biomass. However, despite its renewable character, the sorbitol electro-oxidation reaction (SOR) has been barely studied, being mostly analyzed using massive or nanoparticulate Pt-based materials, exhibiting poor activity. This work proposes the green synthesis of Au/C, Pd/C and Au–Pd/C nanomaterials as alternative electrocatalysts to Pt, and evaluation of their activity for sorbitol electro-oxidation. These nanomaterials were synthesized using 2-hydroxy ethylammonium formate protic ionic liquid, and according to TEM micrographs, these materials presented particle sizes from 13 to 22\u202fnm. The electrocatalytic evaluation of SOR at room temperature indicated that Pd/C had almost 3.5-fold higher current density than a commercial Pt/C. Au/C had similar activity than Pt/C, while Au–Pd/C presented 2-fold higher current density than Pt/C at a lower overpotential (60\u202fmV). The activity for SOR of these materials was extended evaluating the electro-oxidation of the main sorbitol byproducts (glucose and gluconic acid). The resulting evaluation indicated that the excellent current density displayed by Pd/C for sorbitol oxidation can be related to a higher electron transfer per sorbitol molecule. In addition, the lowest overpotential presented by Au–Pd/C was associated with its ability to carry the dissociative adsorption of polyalcohols, which was confirmed using ethylene glycol as a simpler polyalcohol than sorbitol. The current density of Pd/C for sorbitol oxidation was 2-fold higher to that obtained for glucose and ethylene glycol, demonstrating the viability of using sorbitol as fuel for energy conversion applications.