Z-scheme photocatalysis and photoelectrochemical platform with a Co3O4-CuO heterogeneous catalyst for the removal of water pollutants and generation of energy

Protection of the environment by increasing the use of renewable energy sources has become a global priority. The use of renewable resources to generate green energy and remove contaminants from water is an ongoing endeavor. Excellent dye degradation and water-splitting performances have been achieved using photocatalysis, a green technology, combined with the use of heterojunction nanocomposites fabricated with urchin-like and spherical morphologies (Co3O4:CuO). In this study, a one-pot solvothermal approach was used to fabricate a Co3O4–CuO heterojunction composite for use as a multifunctional substrate in dye degradation and photoelectrochemical (PEC) water splitting. For dye degradation, the weight percentage of CuO was adjusted against that of Co3O4; the fabricated CuO–Co3O4 (7.5 wt%) catalyst facilitated 82% degradation of azo dye within only 2 h. The improved catalyst was also used to degrade rhodamine B (76%), methylene blue (71%), and methyl orange (79%). Moreover, owing to its excellent photogenerated charge transfer kinetics and separation capability, the Co3O4–CuO photoelectrode exhibited a higher photocurrent density than the pristine materials in PEC water splitting. Linear sweep voltammetry under light illumination revealed that the photoresponse current of the multifunctional Co3O4–CuO composite was 6.05 mA/cm2 at a potential of 1.8 V (vs. Ag/AgCl), which is ∼2.01 and 3.1 times higher than those of pristine Co3O4 and CuO catalysts, respectively. The photocurrent response of the composite was 3.9 times higher than that under dark conditions. The substantial advantages offered by the fabricated composite over the pristine materials (Co3O4 and CuO), as well as its degradation and PEC water splitting capabilities, were attributed to the combined impact of numerous reactive sites, effective charge separation, increased light harvesting, and facile reactant transfer. Consequently, our research provides novel insights into the fabrication of unique binary nanocomposites with multiple applications and outstanding photocatalytic performance.