Decoration of ZnO\nNanorod Arrays with Heterojunction\nof Graphene Quantum Dots and MoS<sub>2</sub> Nanoparticles for Photoelectrochemical\nWater Splitting

Conversion of sunlight to a chemical fuel through photoelectrochemical\n(PEC) water splitting is deemed to be a promising solution to satisfy\nfuture energy needs. In this study, a photoanode based on the triple\nheterojunction of MoS<sub>2</sub>/graphene quantum dots/ZnO nanorods\n(MoS<sub>2</sub>/GQD/ZnO) was prepared to compare its PEC performance\nwith its well-studied two component counterparts and pristine ZnO.\nIn this hybrid configuration, ZnO nanorods mainly act as the scaffold\nfor further deposition steps, GQDs act as the charge transport layer,\nand MoS<sub>2</sub> nanoparticles act as the visible light absorber.\nAfter the addition of GQDs and MoS<sub>2</sub> nanoparticles to ZnO\nnanorods through electrophoretic deposition, the suitable band alignment\nbetween these materials along with the formation of a type-II junction\nbetween each of the two parts highly facilitates charge separation\nand increases the carrier density. Although GQD/ZnO and MoS<sub>2</sub>/ZnO exhibit superior performance compared to bare ZnO, the formation\nof a triple structure outperforms the former photoanodes in terms\nof overpotential and kinetics. Consequently, MoS<sub>2</sub>/GQD/ZnO\nrepresented the highest efficiency and generated 4.36 mA/cm<sup>2</sup> photocurrent density, which is 4.1 and 1.3 times higher than that\nof GQD/ZnO (1.07 mA/cm<sup>2</sup>) and MoS<sub>2</sub>/ZnO (3.66\nmA/cm<sup>2</sup>) photoanodes, respectively.