Catalytic Activity Analysis of Uniform Palladium Nanoparticles Anchored on Nitrogen-Doped Mesoporous Carbon Spheres for Oxygen Reduction Reaction

Abstract

Palladium (Pd)-based catalysts, as an ideal alternative to platinum (Pt) for oxygen reduction reaction (ORR), have been the focus of recent research because of their comparable catalytic activities, low cost, and abundant resource. Unfortunately, Pd is easy to suffer from agglomeration because of the decrease of their excessive metal surface free energy at elevated temperature, dramatically reducing their catalytic activities for ORR. Herein, we report a facile in-situ self-assembly strategy coupled with the annealing method to synthesize the well-dispersed Pd nanoparticles on nitrogen-doped mesoporous carbon spheres (Pd-NMCS) catalysts, and analyze the catalytic activities for ORR. More importantly, the nitrogen atoms in the NMCS can expose more basic/catalytic sites that can coordinate with Pd nanoparticles to form the strong Pd-N interactions, which can not only tightly anchor Pd nanoparticles but also be advantageous to show outstanding stability and good resistance to methanol crossover. As expected, the obtained Pd-NMCS exhibit good ORR catalytic activities, desirable reaction kinetics, excellent stability, as well as better methanol tolerance, which may offer potential for the practical application of fuel cells. The existence of strong Pd-N interaction enables the Pd nanoparticles to uniformly disperse on the NMCS (Pd-NMCS), thus achieving good ORR catalytic activities, desirable reaction kinetics, outstanding stability as well as better tolerance to methanol crossover of the Pd-NMCS catalyst in the alkaline condition.