Electro-catalytic activity enhancement of Pd–Ni electrocatalysts for the ethanol electro-oxidation in alkaline medium: The promotional effect of CeO2 addition

Pd–Ni alloy catalysts with CeO2 modification are prepared for the ethanol oxidation reaction (EOR) in alkaline electrolyte through the extensively utilized deposition–precipitation route. The structures, morphologies, surface compositions and catalytic activities of the un-modified and Ce-modified Pd–Ni alloy catalysts have been characterized by XRD, TEM, temperature programmed reduction (TPR) and electrochemical measurements, respectively. Physical characterizations show that the 5 wt.% of CeO2 addition (Ce5) can not only decrease the particle size of Pd–Ni but also promote the formation of surface Pd–Ni alloy species and amorphous NiO. CO stripping measurements and EOR results confirm that the surface Pd–Ni alloy and NiO species on Ce5 can modify the adsorption capacity toward ethanol, provide an oxygen source for CO oxidation at low potential, and thus accelerate the decomposition rate toward ethanol. In addition, the long-term durability of Ce5 is also improved due to its specific surface compositions. On the other hand, the excessive CeO2 may result in blocking the active sites and alternation in surface conditions in which the Pd–Ni rich surface species gradually converts to only Pd ones, thereby leading to the significant deterioration of EOR activity.