Insights into Transformation of Icosahedral PdRu Nanocrystals into Lattice-Expanded Nanoframes with Strain Enhancement in Electrochemical Redox Reactions

Bimetallic icosahedral nanoframes have three-dimensional open structures, a high surface-area-to-volume ratio, and high surface site availability. Twin boundaries in these structures cause surface lattice expansion that leads to tensile strain over the nanoframes, which can improve their catalytic activity; however, robust methods for their synthesis in most metal systems are still lacking. In this work, we demonstrate a one-step synthetic strategy for the synthesis of both closed solid and hollow frame icosahedral PdRu nanoparticles (INPs) via a two-stage process of growth and dissolution. By extraction at different reaction times, INPs, concave-faceted icosahedral PdRu nanoparticles (CINPs), and icosahedral PdRu nanoframes (INFs) are obtained. High-angle annular dark-field scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy and inductively coupled plasma–optical emission spectrometry analyses show that the icosahedral nanostructures are PdRu alloys with ∼5 at. % Ru relative to Pd. We also carried out the electrochemical ethanol oxidation reaction (EOR) and CO2 reduction reaction over three types of catalysts, PdRu INPs, PdRu CINPs, and PdRu INFs, as well as commercial Pd NPs, to examine their catalytic properties. PdRu INFs showed a much higher mass activity than PdRu INPs, PdRu CINPs, and Pd NPs in the EOR. PdRu INFs exhibited the highest Faradaic efficiency of CO gas (34%), which suggests that the expansive strain in the framework catalyst structure improves selectivity and activity for CO2 conversion.