Self-assembly birnessite/P25 heterostructures improve charge transmission for photocatalytic degradation of organic pollutants

Developing photocatalysts with a high photocatalytic reaction rate (PRR) still faces serious challenges, such as increasing light absorption capability (LAC) without decreasing internal quantum efficiency (IQE). It is an effective method to construct heterostructures to enhance the electron transfer process for improving their photocatalytic activity under visible light irradiation. Herein, the self-assembly birnessite/P25 (TiO2) hetero-structures (BPHs) have been synthesized by a simple hydrothermal method with the addition of different concentrations (molar ratio of KMnO4: P25 = 30:1, 30:5, and 30:10, respectively) of P25 nanoparticles, which is marked as Bir/P25-1, Bir/P25-2, and Bir/P25-3, respectively. Compared with birnessite, the photocurrent value of Bir/P25-2 is 4.59 times that of birnessite, and the band gap of Bir/P25-2 is 1.7 times that of birnessite, representing greater charge separation efficiency. Furthermore, the photocatalytic performances of HCHO oxidation and methylene blue (MB) degradation were evaluated. The Bir/P25-2 showed 98% of HCHO conversion with 80 ppm of HCHO and corresponding gas hourly space velocity (GHSV) of 60 L/(g.h) at ambient temperature under visible light irradiation. The conversion is much higher than those of birnessite and P25-TiO2, (57 % and 28 %, respectively). Moreover, it could degrade MB (20 mg/L, aqueous pH = 6) completely in 40 min