Influence of ZnO Surface Modification on the Photocatalytic Performance of ZnO/NiO Thin Films
Charge carrier separation is considered as a key factor in enhancing the photocatalytic process and can be maximized by mitigating surface recombination. Following this idea, the surface of zinc oxide (ZnO) was modified by thermal treatment and nickel oxide (NiO) deposition. The influence of the ZnO thermal treatment and NiO deposition conditions on the ZnO surface chemistry and heterostructure interface properties were investigated by in situ X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) and correlated to the dye photodegradation efficiency. The XPS analysis confirmed a change of doping of ZnO after thermal treatment, which mainly influenced the developed band bending, and has led to an improved photocatalytic activity. For the same reason, the heterostructures based on the surface cleaned ZnO surface had higher photocatalytic efficiency than the ones based on non-cleaned ZnO. The temperature input during NiO deposition had negligible effect on the heterostructure interface properties. The photocatalytic efficiency did not follow the band bending evolution because of a dominant contribution of charge recombination across the NiO layer as indicated by PL analysis.
KeywordsHeterogeneous catalysis Catalysis Thin films Methodology and phenomena XPS Microscopy Spectroscopy and general characterisation Photoluminescence ZnO/NiO Surface modification Band bending Photocatalytic activity
This work was carried out in the framework of EJD-FunMat (European Joint Doctorate for Multifunctional Materials) and has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska Curie Grant Agreement No. 641640.
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Conflicts of interest
The authors declare no conflict of interest.
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