Electrocatalytic Oxidation of Glycerol to Value-Added Compounds on Pd Nanocrystals

Abstract

Pd octahedral, rhombic dodecahedral, and cubic nanoparticles (PdOCTA, PdRD, and PdCUBE NPs) were synthesized, characterized, and studied as catalysts for the glycerol electrooxidation reaction (GEOR) in a strongly alkaline medium at 20 and 60 °C. The highest mass activity of 0.050 and 0.183 mA/μgPd was observed on PdOCTA at 20 and 60 °C, respectively, whereas PdCUBE exhibited the highest specific activity of 1.49 and 12.84 mA/cmPd2, respectively. The GEOR products were analyzed by high-performance liquid chromatography (HPLC), and their selectivity and overall glycerol conversion were evaluated at 0.86 V vs RHE. The selectivity toward the three-carbon chain (C3) GEOR products was similar for the different types of catalysts, with PdOCTA and PdCUBE NPs achieving more than 50% selectivity at 20 °C and more than 60% at 60 °C. Glycerate was the overall dominant product for all catalysts, with a selectivity of up to 42%. The glycerol conversion was found to be highest for PdOCTA─21% at 20 °C and 82% at 60 °C, while PdRD was the least active and showed less than 3% conversion at 20 °C and 35% at 60 °C. Based on the GEOR product distribution, a reaction mechanism was proposed.