Sol-gel processed Er³⁺ doped β-Bi₂O₃ thin films for enhanced visible-light photocatalysis

Er 3+ doped β-Bi 2 O 3 thin-film photocatalysts were obtained through a sol-gel chemical route. The phase structure and light absorption properties were characterized by XRD and UV-Vis spectroscopy. Visible-light photocatalytic activity was assessed via Rhodamine B (RhB) and methyl orange (MO) degradation experiments. For practical applications, the reusability of the Er 3+ doped β-Bi 2 O 3 catalyst was also investigated. Results showed that the presence of Er 3+ induced a progressive cell contraction and binding energy shift because of its incorporation into the β-Bi 2 O 3 lattice in substitutional sites. The doped β-Bi 2 O 3 with 1at% of Er 3+ exhibited the highest photodegradation efficiency (95% for RhB and 85% for MO). The reaction kinetics analysis showed that the photocatalytic degradation of the target pollutant followed pseudo-first-order kinetics and Er 3+ doped β-Bi 2 O 3 (1 at%) exhibited the highest reaction rate constant. The recycling test results demonstrated that the Er 3+ doped β-Bi 2 O 3 exhibited excellent stability. The improved performance of Er 3+ doped β-Bi 2 O 3 can be attributed to two main reasons: (1) efficient charge carrier separation caused by Er 3+ doping, and (2) the modification of band structure and optical absorption range.