Engineering of Gd/Er/Lu-triple-doped Bi2MoO6 to synergistically boost the photocatalytic performance in three different aspects: Oxidizability, light absorption and charge separation

Lanthanide doping is an effective and controllable approach for optimizing the oxidation ability, light absorption and charge separation of photocatalysts. However, the multiple drawbacks of mono-component photocatalysts have not been adequately resolved by the doping of only one or two lanthanide ions. Herein, a novel Gd/Er/Lu-triple-doped Bi2MoO6 photocatalyst was synthesized using a hydrothermal method. The results of trapping and 4-Chlorophenol degradation experiments suggested that the oxidizing efficiency of Bi2MoO6 was clearly enhanced by the generation of hydroxyl radicals after doping with the Gd3+ redox centers. The obtained diffuse reflectance spectra demonstrated that introducing Er3+ ions provides energy upconversion centers to improve light absorption. The obtained X-ray photoelectron and photoluminescence spectra demonstrated that abundant oxygen vacancies were produced in the Bi2MoO6 crystal after the doping of Lu3+ ions, contributing to promoting the separation of charge carriers. In summary, Gd/Er/Lu-triple-doped Bi2MoO6 displays much better photocatalytic performance than single- and double-doped Bi2MoO6 materials, which is attributed to the synergistic effects of the Gd3+, Er3+ and Lu3+ ions. These discoveries demonstrate a novel synergistic effect of the redox centers (Gd3+ doping), energy upconversion (Er3+ doping) and oxygen vacancies (Lu3+ doping) for the design and fabrication of high-efficiency photocatalysts.