Synthesis of CuO and Cu2O nano/microparticles from a single precursor: effect of temperature on CuO/Cu2O formation and morphology dependent nitroarene reduction

摘要

CuO and Cu2O nano/microparticles with pure phases have been synthesized from the same precursor by a hydrothermal method. Hydrothermal heating of Cu(OAc)(2) produced CuO at 125 degrees C whereas pure Cu2O was obtained at 175 degrees C. Heating at 150 degrees C gave a CuO/Cu2O mixture. In contrast, Cu(acac)(2) produced only Cu2O at all three temperatures. The pure phases of Cu2O and CuO nano/microparticles were confirmed by PXRD and XPS characterization. The mechanistic studies indicate that decomposition of the organic anion/ligand of the Cu-precursor played a key role in the formation of CuO/Cu2O nano/microparticles from Cu(OAc)(2)/Cu(acac)(2). FE-SEM studies revealed the formation of CuO with a microsphere morphology (125 degrees C) and a micro-cup for Cu2O at 175 degrees C. Nanowires and micron-sized elliptical cylinders were observed for Cu2O synthesized from Cu(acac)(2). However, calcination of Cu(OAc)(2), Cu(acac)(2) and Cu(NO3)(2) at 500 degrees C produced crystalline CuO nano/microparticles with various sizes and morphologies. Further, CuO nano/microparticles investigated for industrially important aromatic nitro to amine conversion showed morphology dependent nitro group reduction. Smaller spherical CuO nano/microparticles obtained from Cu(acac)(2) exhibited the highest catalytic activity. The reusability studies indicate that CuO nano/microparticles can be used for up to six cycles. Thus we have presented a simple method to synthesize Cu2O or CuO from the same precursor and demonstrated the morphology dependent catalytic activity of CuO nano/microparticles.