Atomic resolution structural insights into PdPt nanoparticle-carbon interactions for the design of highly active and stable electrocatalysts

摘要

Interfacial interactions between sub-4 nm metal alloy nanoparticles and carbon supports, although not well understood at the atomic level, may be expected to have a profound influence on catalytic properties. Pd_3Pt_2 alloy particles comprised of a disordered surface layer over a corrugated crystalline core are shown to exhibit strong interfacial interactions with a ～20-50 nm spherical carbon support, as characterized by probe aberration corrected scanning transmission electron microscopy (pcSTEM). The disordered shells were formed from defects introduced by Pd during arrested growth synthesis of the alloy nanoparticles. The chemical and morphological changes in the catalyst, before and after cyclic stability testing (1000 cycles, 0.5-1.2 V), were probed with cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and pcSTEM. The strong metal-support interaction, along with the uniform alloy structure raised the mass activity by a factor of 1.8 versus pure Pt. The metal-support interactions also mitigated nanoparticle coalescence, dissolution, and ripening, resulting in only a 20% loss in mass activity (versus 60% for pure Pt on carbon) after the cyclic stability test. The design of alloy structure, guided by insight from atomic scale pcSTEM, for enhanced catalytic activity and stability, resulting from strong wetting with a deformable disordered shell, has the potential to be a general paradigm for improving catalytic performance.