Ternary PdNiO nanocrystals-ornamented porous CeO2/onion-like carbon for electrooxidation of carbon monoxide: unveiling the effect of supports and electrolytes

Abstract

Porous ternary Pd-based catalysts are highly promising for various electrocatalytic applications, due to their low Pd mass, high surface area, accessible active sites, and tunable electronic structure; however, their activity for CO oxidation (COoxid) in different electrolytes is yet to be reported. Herein, ternary PdNiO nanocrystals supported on porous CeO2/onion-like carbon nanostructures (PdNiO-CeO2/OLC) were prepared by the sol-gel and impregnation approaches for electrochemical COoxid in different electrolytes at room temperature. Notably, porous CeO2/OLC acts as a support and nanoreactor for supporting the growth of PdNiO without the need for reducing agents or surfactants. The as-obtained PdNiO-CeO2/OLC had a porous sponge-like structure composed of ultra-small PdNiO nanocrystals (8 ± 1 nm) distributed on porous flower-like CeO2 and OLC, which possessed unique merits of multifunctional structure, clean surface, low mass of Pd (10 wt%), porosity (0.30 cm3 g−1), and high surface area (155.66 m2 g−1). The COoxid activity of PdNiO-CeO2/OLC was higher than those of PdNiO/OLC, PdNiO-CeO2, and commercial Pd/C catalyst, owing to the electronic interaction of PdNiO with CeO2/OLC support, which eases CO adsorption/activation alongside activation/dissociation of H2O to generate active oxygenated species (i.e., OH) needed for accelerating COoxid kinetics. The COoxid activity of PdNiO-CeO2/OLC in acidic electrolyte (HClO4) was better than those in alkaline (KOH) and neutral (NaHCO3) electrolytes. This study may open new doorways for understanding the effect of electrolytes and supports on the COoxid activity of porous ternary Pd-based catalysts.