Interface optimization of ZnO nanorod/CdS quantum dots heterostructure by a facile two-step low-temperature thermal treatment for improved photoelectrochemical water splitting

- A facile low-temperature thermal treatment is proposed for interface modification.
- PEC performance can be dramatically improved by the two-step annealing process.
- Interface optimization by the thermal treatment plays a key role in PEC enhancement.
- First-principles calculation supports the importance of interface modification on improving photoelectric properties.

A simple and efficient low-temperature thermal treatment process has been demonstrated to dramatically improve the photoelectrochemical (PEC) performance of ZnO nanorod/CdS quantum dots heterostructure. The ZnO/CdS heterojunction was sequentially fabricated by atomic layer deposition, hydrothermal method and successive ionic layer adsorption-reaction method. In contrast to the traditional annealing usually conducted in muffle furnace at high temperature, a two-step low-temperature thermal treatment has been first carried out just on a hot plate at 150 °C for 10 min and then 250 °C for another 10 min, which significantly enhanced the PEC performance of the ZnO/CdS photoanodes. The optimal photocurrent density and the corresponding photoconversion efficiency can reach 9.16 mA cm−2 (0.4 VSCE) and 4.03% under a standard simulated illumination condition (AM 1.5 G, 100 mW cm−2), which improved 75% and 44% as much as those of the unheated sample. The incident photon-to-current efficiency (IPCE) is raised up to 95% at 350 nm. These are one of the best results ever reported on the similar ZnO/CdS photoanodes. Systematic PEC experiments attribute the enhancement to the optimized interface between ZnO and CdS by the thermal treatment which can promote charge carrier separation and transportation. Further theoretical calculation confirms the importance of the interface modification on improving the photoelectric properties. The two-step low-temperature thermal treatment thus presents a facile method for the design and optimization of high-performance PEC photoelectrodes.

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