Highly Catalytic Pd−Ag Bimetallic Dendrites

Abstract

Pd−Ag bimetallic dendrites have been synthesized via a galvanic replacement reaction of Ag dendrites in a Na2PdCl4 solution. Scanning and transmission electron microscopy (SEM and TEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis reveal that the resulting product is composed of partially depleted Ag dendrites covered with a rough surface with many Pd granules protruding by up to about 20 nm. High-solution TEM combined with EDX and selected area electron diffraction (SAED) confirms the formation of bimetallic interfaces between Pd and Ag. These Pd−Ag dendrites show up to four times higher catalytic activity toward the reduction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH4) than the best recently reported catalysts. This further enhancement over the already strong performance of similarly synthesized Au−Ag dendrites is explained by the presence of Pd, adding a hydrogen relay mechanism on top of the very effective electron relay capability of bimetallic dendrites.