Regulate the crystal and optoelectronic properties of Bi2WO6 nanosheet crystals by Sm3+ doping for superior visible-light-driven photocatalytic performance

A series of novel Sm3+/Bi2WO6 nanosheets were successfully fabricated by a facile hydrothermal route. A number of physical chemistry characterizations and photocatalytic performance test showed that the doping of Sm3+ ions into Bi2WO6 caused the lattice contraction of Bi2WO6 crystal, which brought about the enhancement of specific surface area and surface OH groups. Moreover, Sm3+ doping strengthened visible light absorption associated with oxygen vacancies. At the same time, oxygen vacancies generated by the substitution of Bi3+ with Sm3+ acted as the positive charge centers to trap the electrons, and consequently increased the life of photogenerated charge carriers. The obtained Sm3+/Bi2WO6 nanosheets were used to degrade different azo dyes, e.g. rhodamine B (RhB), methylene blue (MB), methyl orange (MO) and acid orange II (AOII). Sm3+(4at%)/Bi2WO6 sample showed the highest degradation activity, similar to 3 times of pristine Bi2WO6 with the degradation rate order of AOII similar to RhB > MB > MO. 100% AOII and RhB can be degraded within 40 min visible light irradiation. Electron spin resonance and active species quenching experiments confirmed that superoxide radicals (center dot O-2(-)) and h(+) were the major radicals for dyes degradation in this Sm3+/Bi2WO6 system.