Solvothermal synthesis of visible-light-active N-modified ZrO2 nanoparticles

• N-modified ZrO2 nanoparticles were prepared by a HNO3-involved solvothermal method.
• Remarkable visible-light-absorbing ability.
• High photocatalytic activity in the reduction of aqueous Cr(VI) under visible-light.

This work reports the synthesis and evaluation of visible-light-active N-modified ZrO2 nanoparticles for photocatalytic reduction of aqueous Cr(VI). Using ZrCl4, absolute ethanol and concentrated (65–68 mass%) nitric acid as the starting materials, a simple low temperature (180 °C) solvothermal method was proposed for the synthesis of N-modified ZrO2 nanoparticles (which were abbreviated as ZrO2–HNO3). The composition, structure, BET specific surface area and optical property of ZrO2–HNO3 were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of ZrO2–HNO3 was tested in the reduction of aqueous Cr(VI) under visible-light (λ>420 nm) irradiation, and compared with that of ZrO2–NH3 (which denoted the product synthesized when 65–68 mass% HNO3was replaced by 25–28 mass% NH3·H2O). It was observed that ZrO2–HNO3 exhibited remarkable visible-light-absorbing ability and high photocatalytic activity, whereas ZrO2–NH3 exhibited little absorption of visible-light and no photocatalytic activity in the reduction of aqueous Cr(VI) under visible-light (λ>420 nm) irradiation. This work suggests that ZrO2–HNO3 is a new promising visible-light-activated photocatalyst.