Photocatalytic Activity of N-Doped ZrO2 Thin Films Determined by Direct and Indirect Irradiation

In this paper, we investigate the decomposition of a toxic organic compound, Rhodamine B, by the photocatalytic activities of undoped and nitrogen-doped ZrO2 thin films, deposited using the HiPIMS technique. The investigation was performed in the presence and in the absence of H2O2, for two types of experimental arrangements: the irradiation of the films, followed by dipping them in the Rhodamine B solutions, and the irradiation of the films dipped in the solution. The two situations were named direct irradiation and indirect irradiation, respectively. Methods like XRD, AFM, XPS, DRS, water/film surface contact angle, and spectrophotometry were used to obtain information on the films' structure, surface morphology, elemental composition of the films surface, optical band gap, hydrophilicity, and photocatalytic activity, respectively. All these properties were described and correlated. By N-doping ZrO2, the films become absorbent in the visible domain, so that the solar light could be efficiently used; the films' hydrophilic properties improve, which is an important fact in self-cleaning applications; and the films' photocatalytic activity for the decomposition of Rhodamine B becomes better. The addition of hydrogen peroxide acted as an inhibitor for all systems and not as an accelerator of the photocatalytic reactions as expected.

Automated summary

This study investigates the photocatalytic activities of undoped and nitrogen-doped ZrO2 thin films in the decomposition of the toxic organic compound Rhodamine B. The effects of direct and indirect irradiation on the films' structure, surface morphology, elemental composition, optical band gap, hydrophilicity, and photocatalytic activity were analyzed using various methods. N-doped ZrO2 films showed improved solar light absorption, enhanced hydrophilicity, and higher photocatalytic activity for Rhodamine B decomposition. Surprisingly, the addition of hydrogen peroxide acted as an inhibitor rather than an accelerator for the photocatalytic reactions.