Morphological Evolution of Cu₂O Nanocrystals in an Acid Solution: Stability of Different Crystal Planes

The morphological evolution of uniform Cu₂O nanocrystals with different morphologies in a weak acetic acid solution (pH = 3.5) has been studied for cubic, octahedral, rhombic dodecahedral, {100} truncated octahedral, and {110} truncated octahedral nanocrystals. Cu₂O nanocrystals undergo oxidative dissolution in weak acid solution, but their morphological changes depend on the exposed crystal planes. We found that the stability of Cu₂O crystal planes in weak acid solution follows the order of {100} ≫ {111} > {110} and determines how the morphology of Cu₂O nanocrystals evolves. The stable {100} crystal planes remain, and new {100} facets form at the expense of the less stable {111} and {110} crystal planes on the surface of Cu₂O nanocrystals. Density functional theory calculations reveal that the Cu−O bond on Cu₂O(100) surface has the shortest bond length. These results clearly exemplify that the morphology of inorganic crystals will evolve with the change of local chemical environment, shedding light on fundamentally understanding the morphological evolution of natural minerals and providing novel insights into the geomimetic synthesis of inorganic materials in the laboratory.