Anti-poisoned oxygen reduction reaction by rice-like Pd–Sb nanoparticles

Abstract

Direct methanol fuel cells (DMFCs) have been widely noticed for high efficiency, energy density, and ultralow emissions, but the poor CH₃OH and CO tolerance, as well as the slow oxygen reduction reaction (ORR) have significantly hampered their continued growth. Herein, a new class of rice-like Pd₂₀Sb₇ nanoparticles (NPs) with high CH₃OH and CO tolerance capacity are reported for the ORR. Specifically, Pd₂₀Sb₇ NPs/C show a great CH₃OH and CO tolerance capability by maintaining almost 100% mass activity of the ORR with 0.5 M CH₃OH and CO, against an obvious decrease for Pd NPs/C and the commercial Pd/C. Even after 10 000 cycles with 0.5 M CH₃OH, Pd₂₀Sb₇ NPs/C still retain ORR activity. X-ray photoelectron spectroscopy studies demonstrate that Sb can successfully adjust the electronic structure of Pd and reduce CO and CH₃OH adsorption, which would contribute to the greatly enhanced CH₃OH and CO tolerance during the ORR. Moreover, density functional theory calculations further reveal that the satisfactory ORR performance of Pd₂₀Sb₇ NPs/C is attributed to the optimized OOH* and OH* adsorption, as well as the adsorption inertness to CH₃OH. This work emphasizes the critical function of Sb in reducing the adsorption energy of CH₃OH and CO to increase the tolerance ability of Pd₂₀Sb₇ NPs/C during the ORR.