Synthesis of porous and nanostructured particles of CuO via a copper oxalate route

CuO have potential applications in various fields, such as gas sensors, solar energy and catalysis. With the aim of trying to obtain CuO with a high specific surface area, an oxalate precipitation route followed by thermal decomposition was studied. Four different copper salts (nitrate, sulfate, chloride, and acetate) were precipitated with sodium oxalate to form copper oxalate, before being decomposed at 275 °C into copper oxide. The different reagent salts all gave very high specific surface areas (> 70 m2/g) with slight differences in the copper oxide morphology. The effect of the initial reagent concentration had a more significant effect on morphology and surface area; cushions were obtained at low concentrations (0.02 M), and spheres at high concentrations (0.10 M with surface areas < 20 m2/g). Also the use of hydroxypropylmethylcellulose (HPMC) gave the expected cubic morphology previously shown due to specific adsorption of the polymer onto the growing crystal. The low specific surface area measured for samples synthesized at high concentration of reagent was related to a significant amount of a secondary phase Cu2O obtained after thermal decomposition, attributed to local inhomogeneities in the precipitated oxalate due to increased precipitation kinetics at the higher concentrations. Finally a very small amount of copper carbonate could be identified by FTIR which did not affect the main powder characteristic (SBET), but helped validate the precipitation mechanism predicted by a previous thermodynamic study.

Graphical AbstractNanostructured CuO with high specific surface areas (SSA > 70 m2/g) were successfully synthesized from four different copper salts (copper nitrate, sulfate, chloride, and acetate) using the oxalate route, after a thermal decomposition at 275 °C.Figure optionsDownload as PowerPoint slide