Pd/CNT Catalysts for Glycerol Electro-oxidation: Effect of Pd Loading on Production of Valuable Chemical Products

Glycerol (C₃H₈O₃), a waste product of biodiesel, is considered as a suitable substrate for electro-oxidation process to generate high value-added products. A suitable active catalyst could improve the yield of desirable organic compounds from electro-oxidation of glycerol. In this work, palladium nanoparticles supported over activated multi-walled carbon nanotubes (MWCNTs) with varying loadings of 5 %–40 % were prepared using chemical reduction method and used to study their potential for electro-oxidation of glycerol to produce various high value-added products. The catalysts were characterized by different physicochemical methods, such as X-ray diffraction (XRD), N₂ adsorption-desorption, and Transmission electron microscopy (TEM), whereas the electro-oxidation activity of the catalysts was analysed using cyclic voltammetry (CV) and chronoamperometry (CA), and the products were identified by high performance liquid chromatography (HPLC). The electrochemical surface area (S_ESA) and mass activity (MA) were increased from 176.98 m² g⁻¹ to 282.29 m² g⁻¹ and 12.22 mA mg⁻¹ to 49.53 mA mg⁻¹ by increasing the Pd-loading from 5 % to 20 %, respectively. While the further increase to 40 % Pd loading, the S_ESA and MA values decreased to 231.45 m² g⁻¹ and 47.63 mA mg⁻¹respectively. The results found that the optimum 20 % Pd-loading showed the excellent electrochemical properties due to uniform distribution of Pd-metal particles over MWCNTs. High performance liquid chromatography (HPLC) showed the tartronic acid, glyceric acid and glyceraldehyde as dominant products. Mechanism of the reaction has also been proposed based on product distribution.