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Thispaper reports a convenient and facile preparation of single-crystallinepalladium with controllable shape based on the reduction of kineticcontrol via hydrochloric acid oxidative etching. The concentrationof HCl added to the reaction solution was found to be crucial forthe shape evolution of palladium nanocrystals from nanocubes boundedby {100} facets to octahedrons by {111} facets. Palladium nanocubescan be readily obtained at a fast reduction rate without the involvementof additional HCl. With the introduction of a certain amount of HClto the precursor solution, truncated nanocubes with {111} facets wereformed, and the increase of HCl led to the slower reduction rate andthe formation of palladium cuboctahedrons enclosed by six {100} facetsand eight {111} facets at the expense of gradual shrinkage of {100}facets. The probable mechanism of morphological transformation wasproposed upon a batch of experiments. The shape-dependent catalyticperformances of as-obtained palladium nanocrystals were investigatedby the structure-sensitive reaction of formic acid oxidation. It wasfound that catalytic activities of palladium nanocrystals displayeda strong dependence on the facets exposed on the surface, and cubicpalladium exhibited the best catalytic performance compared with cubooctahedraland octahedral palladium nanocrystals. [ABSTRACT FROM AUTHOR]