Highly efficient photocatalytic activity and mechanism of novel Er3+ and Tb3+ co-doped BiOBr/ g-C3N5 towards sulfamethoxazole degradation

Bismuth oxyhalides (BiOX (X = Cl, Br, I) are considered to be an important p-type semiconductors in the photocatalysis applications. In particular, tetragonal BiOBr is considered as a stable photocatalyst due to its resilient absorption in the visible region with an band gap energy of 2.8 eV. In the meantime, lanthanide ions (with 3+ oxidation state) implies as conversion catalyst gained huge impact and remain a serious topic in materials chemistry. Here we synthesized upconversion photocatalyst mainly consists of BiOBr with the Er 3+ and Tb 3+ ions along with low band gap g-C 3 N 5 for the improved photocatalytic performances. The synthesized Er 3+ /Tb 3+ @BiOBr-g-C 3 N 5 heterojunction was systematically characterized by XRD, and FT-IR for the confirmation of the composite and their morphology were analysed with FESEM and HR-TEM analysis which revealed that the sheets of g-C 3 N 5 were decorated by Er 3+ /Tb 3+ loaded BiOBr microspheres. The XPS analysis confirmed the suitable oxidation state of all the individual elements existing in the composite. As the UV-DRS analysis showed that the band gap of the Er 3+ /Tb 3+ BiOBr-gC 3 N 5 heterojunction was narrowed to 2.64 eV. To evaluate the photocatalytic efficiency of the synthesized g-C 3 N 5 , Er 3+ /Tb 3+ @BiOBr and Er 3+ /Tb 3+ @BiOBr-gC 3 N 5 heterojunction under the simulated visible light irradiation source towards the aqueous sulfamethoxazole degradation. The Er 3+ /Tb 3+ @BiOBr-gC 3 N 5 heterojunction shows maximum degradation efficiency of 94.2% after 60 min of visible light irradiation whereas the pure g-C 3 N 5 provided about 43.8% and Er 3+ /Tb 3+ @BiOBr implies 55.2% degradation efficiency. The plausible degradation mechanism of pollutant removal was proposed. • Er 3+ /Tb 3+ BiOBr/g-C 3 N 5 photocatalysts exhibit highly efficient visible light photoactivity. • The Er 3+ and Tb 3+ doping can convert NIR light to UV/vis light for enhanced photoactivity. • The catalysts showed efficient photocatalytic performances for sulfamethoxazole degradation. • The decreased band gap E g and improved charge separation played a major role in the enhanced photoactivity.