Atomic Molar Ratio Optimization of Carbon Nanotube Supported Pdauco Catalysts for Ethylene Glycol and Methanol Electrooxidation in Alkaline Media

Abstract

In this study, carbon nanotube supported Pd, PdAu, and PdAuCo electrocatalysts (Pd/CNT, PdAu/CNT, and PdAuCo/CNT) were synthesized via NaBH4 reduction method at varying molar atomic ratios to investigate their performance for methanol and ethylene glycol electrooxidation in alkaline media. The characterization of the as-prepared catalysts was performed using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, N-2 adsorption-desorption, and small-angle X-ray-scattering analysis. From the physical characterization results, it was seen that PdAuCo/CNT catalysts were successfully prepared. X-ray photoelectron spectroscopy results showed that Pd and Au atoms employed in the preparation of the catalysts exist mainly in their elemental state. X-ray diffraction results indicated the formation of a new phase. Furthermore, the mean particle size of Pd50Au30Co20/CNT was determined as 7.9 and 8.7nm using small-angle X-ray scattering and transmission electron microscopy analyses. Pd50Au30Co20/CNT demonstrated the type V adsorption isotherms with H1-type hysteresis, which indicates the mesoporous structure of the catalyst. Electrocatalytic activity of the catalysts for ethylene glycol and methanol electrooxidation was investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic activity of Pd50Au30Co20/CNT was determined as 262 and 694mA/mg Pd for methanol and ethylene glycol electrooxidation. In accordance with cyclic voltammetry and electrochemical impedance spectroscopy results, Pd50Au30Co20/CNT possesses the highest electrocatalytic activity for both electrooxidation.