Fabrication of bismuth molybdate photocatalyst co-substituted by gadolinium and tungsten for bismuth and molybdenum: Design and radical regulating by the synergistic effect of redox centers and oxygen vacancies for boosting photocatalytic activity

Abstract

Abstract Substitutive doping is a fundamental approach to introduce dopants into a crystalline structure, which resulted in generating the abundant redox centers or oxygen vacancies to promote the separation of photogenerated charge carriers. However, the recombination rate of electron–hole pairs in the single-substituted photocatalysts remained high, thus co-substituting of two sites could be further synergistically restraining the recombination of electron–hole pairs. Herein, the bismuth molybdate (Bi2MoO6) photocatalyst, co-substituted by Gd3+ and W6+ ions for Bi3+ and Mo6+ ions, was synthesized using a hydrothermal method. X-ray photoelectron spectra indicated that the abundant oxygen vacancies were generated in the crystalline Bi2MoO6 after introducing W6+ ions, and these vacancies adsorbed the extensive O2 molecules. Additionally, the results of photoluminescence spectra, photocurrent response and trapping experiments demonstrated that the new hydroxyl radicals can be generated by introducing Gd3+ ions, while the introducing of W6+ ions contributed to enhancing the productivity of • O 2 − radicals; these two species together promoted the separation and transfer of electron–hole pairs. The results of photocatalytic experiments displayed that Gd/W co-substituted Bi2MoO6 shows much better visible-light photocatalytic activity. These findings developed a novel synergistic effect between redox centers (Gd substitution) and oxygen vacancies (W substitution) to design the high-efficiency photocatalysts.