Low temperature–controlled synthesis of hierarchical Cu2O/Cu(OH)2/CuO nanostructures for energy applications

Nano-forms of copper oxides (CuO and Cu 2 O) are potential candidates in the field of energy conversion and storage. Low temperature and controlled growth of three-dimensional nanostructured hierarchical assembly of CuO over Cu 2 O is reported here with demonstrated advantage in energy conversion and storage applications. Electrodeposited Cu 2 O is partially oxidized in an alkali bath to two different forms of hierarchical nanostructures (HNS): CuO/Cu 2 O and CuO:Cu(OH) 2 /Cu 2 O. Randomly oriented nanorods and nanoflakes with high surface area tussock-like nanostructure are formed during oxidation at room and at elevated temperatures, respectively. The nanoflake morphology exhibits a high surface area of 85.82 m 2 /g and sufficient ion percolation pathways, leading to an efficient electrode–electrolyte interface for electrochemical energy devices. A favorable conduction and valence band alignment in the HNS with respect to water redox level along with fast electron diffusion time of 0.8 μs make it an ideal photocathode.