Electrocatalytic Oxidation of Glycerol on Platinum

Glycerol, a surplus byproduct of biodiesel production, is a promising energy source for fuel cells. However, the low selectivity toward the complete-oxidation product, carbon dioxide (CO ₂ ), hinders the electro-oxidation of glycerol. In this work, we combine spectro-electrochemical studies of extended surfaces using sum frequency generation and product-resolved electrocatalytic measurements on high-surface-area catalysts under potentiostatic conditions to investigate the glycerol oxidation reaction on platinum (Pt). We observed adsorbing carbon monoxide (CO) as the reaction intermediate at potentials as low as 0.05 V (vs the reversible hydrogen electrode; the same potential scale is used throughout this discussion unless otherwise specified) on polycrystalline Pt electrode, indicating that cleavage of the C-C bond in glycerol is feasible on Pt. This observation is in contradiction to the low selectivity toward CO ₂ (with a faradaic efficiency of <4%) measured by the electrocatalytic studies on Pt/C. The discrepancy is ascribed to the rather feasible cleavage of one terminal carbon to form∗CO, but kinetically hindered oxidation of∗CO and further dissociation of the remaining C ₂ fragments at low potentials, whereas at high potentials partial oxidation pathways become more favorable due to suppressed C-C bond cleavage.