Electrocatalytic CO oxidation on porous ternary PdNiO-CeO2/carbon black nanocatalysts: Effect of supports and electrolytes

Abstract

The catalytic activity and durability of porous ternary Pd-based electrocatalysts are augmented by alloying with other metals and using supports, however, the effect of supports and electrolytes at varied pH on the electrochemical CO oxidation (COOxid) performance is not yet studied. Herein, a PdNiO-CeO2/CB nanosphere, composed of PdNiO nanocrystals sprouted on CeO2 flake-like and carbon black (CB) nanosheets, was synthesized by a sol-gel and impregnation methods. Remarkably, during the impregnation step, CeO2/CB serves as a reactor for the reduction of Pd/Ni precursors and supported the growth of PdNiO nanocrystals without surfactant and/or reducing agent. This endowed the formation of PdNiO-CeO2/CB with multifunctional porous structures, including pore volume (0.29 cm3/g) and specific surface area (151.86 m2/g) and a clean Pd surface. The as-prepared PdNiO-CeO2/CB delivers a superior COOxid activity than those of PdNiO-CeO2, PdNiO/CB, and commercial Pd/C in acidic (HClO4), neutral (NaHCO3), and alkaline (KOH) electrolytes, ascribable to the oxygen-enriched support (CeO2) and its interaction with CB support along with electronic effect of PdNiO, which enhances the CO adsorption/activation and simultaneously activates/splits H2O to produce active oxygenated species required for hastening COOxid kinetics. Interestingly, the COOxid performance of the PdNiO-CeO2/CB in HClO4 electrolyte was higher than those in NaHCO3 and KOH electrolytes. This study reveals that coupling oxygen-enriched support (CeO2) with CB support is preferred for the enhancement of the COOxid activity of PdNiO nanocrystals.