Anion-induced morphological regulation of cupric oxide nanostructures and their application as co-catalysts for solar water splitting.

Morphological control of nanomaterials is essential for their properties and potential applications, and many strategies have been developed. In this work, a new strategy for simultaneously preparing and modulating the morphological structure evolution of copper layered hydroxyl salts and oxides is introduced. By changing the nature of the anions in the electroplating solution, significant variations in the size and porosity of nanosheets are achieved. Porous CuO nanosheets with a higher surface area were obtained by the use of copper nitrate as a copper source, while CuO nanoflakes were produced from copper sulfate. Photoanodes combining these porous CuO nanomaterials and a typical light absorber (BiVO4) exhibited good morphology-dependent activities for photoelectrochemical water splitting. The composite electrode displays a negative shift of 180 mV for the onset potential and an approximately 2-fold enhancement in the photocurrent compared to the bare BiVO4. The charge recombination rate in the photoelectrode with the porous CuO nanosheets was significantly lower than the bare photoanode due to the favorable electron diffusion path and effective charge collection. This research offers an effective method for constructing a highly active photoelectrocatalytic system for overall water splitting.