La2O3-modified graphite carbon nitride achieving the enhanced photocatalytic degradation of different organic pollutants under visible light irradiation

Abstract

Lanthanum (La) has some advantages of smaller radius, cheaper price and higher affinity for oxygen in rare-earth-metallic element group, and La2O3 modification may be helpful to further extend the life of photon-induced electrons and holes due to its rich energy levels, special optical properties and 4f electronic transition properties. Inspired by these items, graphite carbon nitride (GCN)/La2O3 (denoted as CN/La) was prepared by a facile hydrothermal method. The characterizations of photocatalysts were conducted using X-ray diffraction, field emission scanning electron microscope, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption-desorption isotherms. The Methyl orange (MO), Methylene blue (MB) and Rhodamine B (RhB) were applied to characterize the photocatalytic performances of CN/La-x% photocatalysts under visible light irradiation (λ > 420 nm). CN/La-6% exhibited the optimal photodegradation efficiency, and 66.6% of MO, 99.5% of RhB and 100% of MB could be removed in 120 min. The BET surface area was improved from 8.357 m2g-1 to 67.818 m2g-1 and the light absorption edge shifted from 468 nm to 484 nm. In addition, the photocurrent density increased from 0.96 μA/cm2 to 4.82 μA/cm2. The improved photodegradation efficiency was attributed to larger BET surface area, extended optical absorption and enhanced charge carrier separation. More interestingly, this work lays the foundation for practical application of the La2O3-modified GCN material as the photocatalytic catalysts.