Fe2O3 hexagonal nanosheets assembled with NiS formed p–n heterojunction for efficient photocatalytic hydrogen evolution.

In the field of photocatalysis, the recombination of photogenerated holes and electrons is still an urgent problem to be solved. Among many measures, constructing heterojunction is one of the commonly used methods to adjust the carrier transfer path and accelerate the electron transfer. In this paper, Fe₂O₃/NiS p–n heterojunction composite catalyst was synthesized by solvothermal method. Through XRD, SEM and XPS characterization and analysis, it was found that the composite catalyst was composed of NiS nanoparticles and hexagonal Fe₂O₃ nanosheets. The specific surface area test results showed that Fe₂O₃/NiS had a larger specific surface area, which could provide more active sites for the H₂ production reaction. By adjusting the ratio between Fe₂O₃ and NiS, the optimal composite photocatalyst was obtained. The hydrogen production rate reached 5.82 mmol g⁻¹ h⁻¹, which was 58.2× that of single Fe₂O₃ and 2.7× that of single NiS. The NiS p-type semiconductor and Fe₂O₃n-type semiconductor were successfully coupled. Under the action of the p–n heterojunction interface and the built-in electric field, the photogenerated electrons and holes of the composite catalyst could be quickly transferred and separated. This result was also confirmed by a series of characterizations such as photoluminescence spectrum and photoelectrochemical experiments. Fe₂O₃ and NiS formed p–n heterojunctions, and the mixed interface structure between them provided a new hydrogen-producing active center for each. Moreover, the construction of p–n heterojunction promoted the separation of electrons (e⁻) and holes (h⁺), so that Fe₂O₃/NiS exhibited excellent hydrogen evolution performance. [ABSTRACT FROM AUTHOR]