Enhancing visible-light-driven water splitting of ZnO nanorods by dual synergistic effects of plasmonic Au nanoparticles and Cu dopants

Converting solar energy into chemical fuels is important to develop renewable energy. Here, Cu-doped ZnO nanorods (NRs) decorated with Au nanoparticles (NPs) are used as an efficient semiconductor catalyst for visible-light-driven water splitting. Doping Cu into ZnO NRs narrows the bandgap and shifts the absorbance toward red light; decorating Au NPs onto the ZnO:Cu NRs enhances the absorbance in the visible region and improves the solar energy conversion. The band gap of the ZnO:Cu NRs is optimized at 3% Cu doping, which presents a minimum value of 3.09 eV. Furthermore, the surface plasmon resonance effect, which is caused by decorating 10-nm Au NPs on the Cu-doped ZnO NRs, enhances the optical absorption and improves the photoelectrochemical water splitting performance. The presence of Au NPs on the surface of the NRs also reduces charge recombination, increasing the photocurrent. Under visible illumination (λ > 420 nm), the considerable photocurrent density of this device reaches 10.2 μA cm⁻² at 0.581 V, which is about 7.3 times higher than that of a pure ZnO NRs sample. The simple and cost-effective fabrication process of this design provides an innovative approach for water splitting and future optoelectronic devices.