Photocatalytic nitrogen fixation on transition metal modified TiO2 nanosheets under simulated sunlight

Abstract

Transition metal (M = Cu, Fe and Ni) modified TiO₂ nanosheets were synthesized via a microwave assisted hydrothermal method. The as-fabricated catalysts were characterized using X-ray diffraction (XRD), electron microscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption, UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence emission (PL), transient photocurrent–time curves and electrochemical impedance spectroscopy (EIS). The results indicated that the loading of transition metals did not influence the crystal structure and morphology of anatase TiO₂, while the specific surface area, the absorption in the visible region and the charge transfer were enhanced. In addition, photocatalytic nitrogen fixation over the transition metal modified TiO₂ nanosheets was also evaluated. Under the irradiation of simulated sunlight, transition metal modified TiO₂ exhibited better photocatalytic performance and stability than pristine TiO₂. Among these samples, Cu/TiO₂ with the optimal mass content of 1.0% achieved the best NH₄⁺ generation performance and the evolution rate reached 6.78 mmol g⁻¹ h⁻¹ with the relative standard deviation of 2.33%. Furthermore, a plausible mechanism coupled with interfacial charge transfer (IFCT) over Cu modified TiO₂ nanosheets was proposed in our present study.