Nanostructured 3-D Nano-Bricks Shaped CuO – 0-D Particle Shaped Co3O4 Composite for Superior Photo-Electrochemical Water Splitting

The construction of novel nanostructures, especially using metal oxides, presents an attractive and affordable strategy to enhance the photoelectrochemical (PEC) water splitting performance. In this study, a 3-D bricks type CuO and 0-D nanoparticle type Co3O4 heterojunction composite was designed via a one -pot hydrothermal synthesis for PEC water splitting applications. The PEC water splitting characteristics, including Linear Sweep Voltammetry (LSV), I -t curves, and Electrochemical Impedance Spectroscopy (EIS), were investigated to evaluate the performance of the nanostructured CuO-Co3O4 composite compared to the pristine nanostructures. The LSV measurements demonstrated that the CuO-Co3O4 composite exhibited a significantly higher current density of 1.29 mA/cm2 (potential V vs Ag/AgCl) compared to pristine Co3O4 and CuO, with improvements of approximately 1.63 and 3.4 times, respectively. Moreover, the I -t curves confirmed the stable photocurrent response of all photoelectrodes, and the CuO-Co3O4 composite showed a photocurrent density of 0.21 mA/cm2 with a 50-s interval. The superior performance of the CuO-Co3O4 composite can be attributed to its visible light absorption characteristics, as confirmed by UV-visible absorption spectroscopy, as well as its lower recombination rate compared to the pristine materials, as analyzed using fluorescence spectroscopy. Additionally, the composite photo-electrode demonstrated excellent stability during on and off light cycles for up to 5 h with a 1-h interval. The successful synthesis of this heterojunction composite with novel nanostructures provides valuable insights for the development of metal oxide nanostructures in the field of PEC water splitting. These findings open new avenues for further research and advancements in the design and fabrication of efficient photoelectrodes for sustainable water splitting applications.