Overall photoelectrochemical water splitting at low applied potential over ZnO quantum dots/nanorods homojunction

The quantum-confinement-tailored band engineering is herein exemplified by the ZnO-based homojunction in a hierarchical form of zero-dimensional quantum dots (QDs) anchored to one-dimensional nanorods (NRs). This structure is characterized via X-ray diffraction and photoluminescence techniques, wherein the transformations in the full width at half-maximum, the peak intensity and spectral profile substantiate its formation. Particularly, the quantum effect manifests evidently in the photoelectrochemial (PEC) measurement, wherein the ZnO QD/NR homojunction is employed as the photoanode for sunlight-driven water splitting. Concretely, the onset potential is negatively shifted with respect to that in the absence of ZnO QDs, facilitating the photocurrent generation at small external bias, as reflected in the applied bias photon-to-current efficiency (ABPE) that exhibits a two-fold enhancement. In addition, an energy gradient is established at the QD/NR interface, favoring the charge separation that is further responsible for the ameliorated PEC performance. In all, the present study put forward a promising alternative to engineer the energy band at the homojunction via readily traversing the boundary between nano- and quantum-scale.