Morphology-controllable Cu2O supercrystals: Facile synthesis, facet etching mechanism and comparative photocatalytic H2 production

Monodisperse Cu2O-cubes, Cu2O-concave cubes and Cu2O-octapods supercrystals have been synthesized successfully using a self-assembly approach in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. Specifically, the supercrystals can be prepared by adding aqueous Cu(Ac)2 solution into butyl alcohol solution of AOT to first assemble nanoreactors and then perform hydrothermal reactions. The structures of the supercrystals can be tailored by simply varying the amount of Cu (Ac)2 with the same ratio of the Cu(Ac)2 to ascorbic acid. AOT surfactant was crucial to precisely control the supercrystal morphology. It was demonstrated that the ratio of growth rate along different planes varied by adjusting the amount of Cu(Ac)2 and the volume ratio of alcohol to water, thus Cu2O crystals with cubes, concave cubes, and octapods with the size of 1.2-2.2 μm were obtained. The morphology evolution from cubes, concave cubes to octapods was systematically studied and a facet etching mechanism is proposed. Hence, precise control of the amount of Cu(Ac)2 enables this facet etching, novel Cu2O with concave {100} facets can be fabricated. Photocatalysis investigation on the morphology-controlled Cu2O indicates that the Cu2O-octapods supercrystals showed the highest amount of H2 and the best cyclic-stability. This work reveals that morphology-control of supercrystals is important to the development of novel photocatalysis.