Flux synthesis of Bi2MO4Cl (M = Gd and Nd) nanosheets for high-efficiency photocatalytic oxygen evolution under visible light

The Bi 2 MO 4 Cl (M = Gd and Nd) nanosheets were prepared by a molten salt flux method for the first time. The resulted Bi 2 GdO 4 Cl (F-BG) nanosheets showed the highest photocatalytic activity for oxygen (O 2 ) evolution and trypan blue (TB) degradation than Bi 2 NdO 4 Cl (F-BN), Bi 2 GdO 4 Cl (S-BG) and Bi 2 NdO 4 Cl (S-BN) synthesized by a solid-state method. The F-BG nanosheets showed the larger specific surface areas and abundant pores, which could provide more reactive sites. The photoelectrochemical and photoluminescence (PL) results revealed that F-BG sample had the excellent separation and transfer rates of photogenerated charge carriers, leading to the highly photocatalytic performance for both O 2 evolution and TB degradation. The UV–Vis diffuse reflectance spectra (DRS) showed all samples had the visible-light-responsive characteristic. The radical trapping experiment revealed hole (h + ) played a major role, while superoxide radical ( \(\cdot {\text{O}}_{{2}}^{ - }\) ) contributed a little to photocatalytic degradation process. Thus, a possible photocatalytic mechanism was proposed based on the radical trapping experiment. This work shows us a useful insight into the preparation of highly active bismuth-based oxyhalide nanosheets photocatalysts by a molten salt synthesis through surface modification and morphology control and provides the possibility of water splitting under visible light.