Ionic Layer Epitaxy of Nanometer-Thick Palladium Nanosheets with Enhanced Electrocatalytic Properties

Large surface area-to-volume ratio with plenty of accessible electrochemically active sites presents metal nanosheets a highly efficient catalyst material. However, a facile and effective synthesis of metal nanosheets with nanoscale thicknesses, macroscopic sizes, and desired crystal facets is still a grand challenge. Here, we report the synthesis of free-standing Pd nanosheets by ionic layer epitaxy (ILE), which employs a cationic oleylamine monolayer at the water–air interface as a soft template to guide the nanosheet growth. The Pd nanosheets exhibited a quasi-square morphology with a uniform thickness of ∼2 nm and sizes ranging from 1 to 6 μm. Owing to the extremely large surface-to-volume ratio and the exposure of mixed surface crystal facets, the Pd nanosheets exhibited high activity in formic acid oxidation compared to the commercial Pd black and other reported Pd nanostructures. This work presents a simple and effective way to prepare metal nanosheets with nanometer-scale thickness control.