Electrocatalytic oxidation of sorbitol on PdxAuy/C bimetallic nanocatalysts

• Pd x Au y /C catalysts were synthesized and tested for the sorbitol electro-oxidation. • The catalysts activity was attributed to strong bimetallic interactions. • Pd 60 Au 40 /C gave up to 209 mA mg −1 at 0.1 V, almost 10-fold higher than Au/C. • Pd 60 Au 40 /C and Pd 40 Au 60 /C maintained 100 % stability after 1000 cycles in 3 M KOH. • The SOR gives value-added by-products like glycerol and glyceraldehyde. In the present work, the sorbitol electro-oxidation reaction (SOR) was studied in alkaline medium employing bimetallic catalysts of palladium and gold (Pd x Au y /C). The activity for SOR was mainly correlated to bimetallic interactions, because the catalysts presented similar characteristics like morphology, average particle sizes (∼10 nm), and metallic mass contents (∼20 wt%). The bimetallic interactions induced changes like shifts in the lattice parameters, as well in Pd binding energies (up to −0.25 eV) and into the reduction peak of Pd oxides during the electrochemical characterization. Pd 40 Au 60 /C and Pd 60 Au 40 /C presented the best activities at 3 M KOH achieving onset potentials of −0.43 V vs. NHE and current densities of 128 and 209 mA mg −1 at a fixed potential of 0.1 V, respectively. Pd 60 Au 40 /C presented almost 3.5-fold more current density than Pd/C, and 10-fold more than Au/C at the same conditions. These materials also displayed superior stability, maintaining their maximum current densities after 1000 cycles in 0.5 M sorbitol + 3 M KOH. The SOR by-products were determined by HPLC and GC/MS, revealing that these catalysts break sorbitol C–C bonds by attacking intermediate carbons (C 3 and C 4 ) and/or by subsequent removal of chain-end carbons. Among the detected by-products, value-added molecules like glycerol, ethylene glycol, formic acid, and γ-butyrolactone were found. In summary, the stability and activity of Pd-based materials make them suitable for the oxidation of sorbitol as a promising alcohol for fuel cell technology.