Construction of rare-metal neodymium-doped ZnO and g-C3N4 Z-type heterostructures enhance the photocatalytic efficiency of methylene blue removal

Abstract

Herein, Nd-ZnO/g-C3N4 (NZCN) composites were obtained by doping rare-earth element Nd with ZnO using a hydrothermal method, coupled with g-C3N4 (CN) electrostatic ultrasonic self-assembly. The NZCN composite exhibited an impressive methylene blue (MB) removal rate of 94.88 %, with a degradation rate of 0.02637 min−1 after 105 min exposure to 500 W xenon lamp irradiations. Comparatively, the degradation rate of MB by the NZCN composite was five and twice times higher than ZnO and CN samples, respectively. This significant improvement can be attributed to the synergistic effect of Nd, ZnO, and CN, which not only widened the light absorption range but also enhanced the density, separation, and transport of photogenerated electrons (e−) and holes (h+), thus improving the photocatalytic performance of the NZCN composites. An in-depth investigation into the photocatalytic reaction process was carried out using free-radical active-species capture experiments, confirming the critical role of h+. Furthermore, the reproducibility and stability of the NZCN composites were assessed over five experimental cycles, demonstrating consistent and stable MB degradation rates of 90.1 % while retaining the crystal structure unchanged. Overall, the construction of rare-earth-metal-doped ZnO and Z-type heterojunctions synergistically improves photocatalytic activity and provides a green and environmentally friendly approach for the removal of organics from wastewater.