Synergetic photocatalytic-activity enhancement of lanthanum doped TiO2 on halloysite nanocomposites for degradation of organic dye

Abstract A reusable and efficient photo-catalyst based on halloysites (HNTs) and La3+ ion-doped TiO2 nanoparticles was prepared using a sol-gel process and a sonochemical method for decomposing organic dyes. As a support, the HNTs increased the adsorption efficiency of substrates, improving the photocatalytic activity of TiO2 nanoparticles by ∼3 times. The La3+ ion doping of TiO2 decreased the bandgap from 3.25 eV to 3.01 eV, expanding the spectral response to the visible region and enhancing the photocatalytic activity under the sunlight by 1.5 times. Through the integration of the halloysite support and the La3+ ion doping of TiO2, the synergistic enhancement of photocatalytic activity was observed and systematically investigated using XRD, Raman spectroscopy, FT-IR, FE-SEM, EDX-TEM, and zeta potential. In this research, we used Rhodamine B molecules as a model pollutant. During the decomposing process, the HNTs enhanced the local dye concentration nearby the photo-catalyst through the electrostatic interaction, thereby boosting the photocatalytic activity by ∼3 times. Additionally, the catalyst can be separated by simple centrifugation and reused at least five recycles without any activity decrease. The halloysite support, the La3+ ion doping of TiO2 and their simple synthesis approach could provide a practical tool for environmental purification in wastewater using sunlight.