Rhodium nanostructures with highly selective morphologies such as cubes, horned particles, dendrites, and network-shaped wires have been achieved through the synergetic effect of sodium lauryl sulfate (SLS) and halogen anions (F-, Cr-, Br-, I-) in a green solvent, water. The effects of SLS and halogen anions were systematically investigated. The electrocatalytic performances of Rh nanostructures toward ethanol oxidation were tested. The results have shown that the rhodium nanostructures displayed shape-dependent properties, and the nanodendrites possessed the maximum catalytic activity.