Highly Dispersed Pd-CeO₂ Nanoparticles Supported on N-Doped Core–Shell Structured Mesoporous Carbon for Methanol Oxidation in Alkaline Media

Abstract

Sluggish kinetics of the methanol oxidation reaction (MOR) at the anode of direct methanol fuel cells (DMFCs) is primarily due to adsorbed CO poisoning of precious metal catalysts. CeO2 is known to provide oxygen containing species to adjacent precious metal sites for facilitating CO removal during the MOR. In this work, highly dispersed Pd nanoparticles surrounded by CeO2 dots were deposited on a core–shell structured and nitrogen-doped mesoporous carbon sphere (NMCS) support, which exhibited encouraging electrocatalytic activity, CO tolerance, and stability for the MOR in alkaline media. The ratios of Pd to CeO2 were found crucial for overall catalytic performance enhancement. When compared to a commercial PtRu/C catalyst, an optimized Pd(20%)-CeO2(20%)/NMCS catalyst presented a comparable CO stripping onset potential, ∼6 times higher peak current density, and enhanced cyclic stability. The unique mesoporous carbon with nitrogen doping also benefits for uniform dispersion of Pd nanoparticles and CeO2 dots. In good agreement with experimental spectroscopy analysis, density functional theory calculations suggest that the strong electronic interactions between Pd and surrounding CeO2, as well as nitrogen dopants in supports, dramatically reduce the adsorption energy of CO at the Pd surface, therefore enhancing CO tolerance of the Pd-CeO2/NMCS catalyst and further improving MOR activity. Using a polymer fiber membrane-based alkaline DMFC, the Pd(20%)-CeO2 (20%)/NMCS anode catalyst further demonstrated encouraging performance when a NiCo2O4 catalyst was used for the oxygen cathode.

Porous Pd‐PdO Nanotubes for Methanol Electrooxidation

“…Membrane electrode assembly was prepared according to previous works. [ 10,16 ] The electrocatalyst slurry was prepared using the following weight ratio: electrocatalyst/isopropanol/water/Nafion (5 wt%) solution of 1/12/12/11. The electrocatalyst slurry was treated by ultrasonic for 2 h and then sprayed onto one side of a carbon paper (TGP‐H‐060, Troay) with an area of ≈5 cm 2 .…”

Advanced Electrocatalysis for Energy and Environmental Sustainability via Water and Nitrogen Reactions

“…[ 254 ] Based on mechanistic understanding, the addition of oxophilic oxide of CeO 2 in Pt catalysts can supply *OH to the active metal surface to facilitate the AOR and other oxidation. [ 230,255 ] Experimentally, the current density on the CeO 2 ‐modified Pt electrode is increased compared to Pt catalysts (Figure 15d). [ 230 ] Other metal oxides, such as Y 2 O 3 , LaO 3 , Sm 2 O 3 , and NiO, play a similar role in promoting the AOR activity of Pt.…”

A comprehensive and critical review on recent progress in anode catalyst for methanol oxidation reaction

“…In order to provide better facility for the oxidation of CO species and reduce poisoning, oxygen containing support was also impregnated with Pt and other precious metals particles, and recently, Qiang's group reported the MOR of highly dispersed Pd-CeO 2 catalyst supported over N-doped core-shell mesoporous carbon sphere (NMCS) support with excellent activity, CO resistance, and stability in alkaline medium. [216] They studied the significance of the atomic ratio of Pd/CeO 2 in catalytic activity and optimized it to 20:20 (Pt( 20%) :CeO 2(20%) /NMCS) that exhibits ~6 times higher peak current density than commercial PtRu/C. Density functional theory calculations were also performed showing a strong electronic interactions between palladium and the surrounding CeO 2 and the N 2 dopants existing in supports significantly decreases the adsorption energy of the carbon monoxide at the surface of palladium.…”