Improved photodegradation efficiency in Fe3+-doped Bi3TiNbO9 nanosheets through oxygen vacancies introduction and ferroelectric polarization enhancement simultaneously

Suffering from wide bandgaps and poor charge carrier mobility, most of the ferroelectric photocatalysts are still faced with low efficiency in spite of the advanced intrinsic ferroelectric polarization. Herein we proposed a simple Fe3+-doping strategy to induce oxygen vacancies and enhance ferroelectric polarization in Bi3TiNbO9 nanosheets simultaneously, realizing band structure modulation and charge carrier kinetics steering. Combining DFT calculations and systematic experimental characterizations, it was demonstrated that the introduction of Fe not only reduce the bandgaps but also improve electron-hole separation. The promoted carrier transport and increased carrier density was related to the Fe3+/Fe2+ redox cycle and oxygen vacancies (OVs) arising from the substitution of Ti4+ with Fe3+. More importantly, the enlarged ferroelectric polarization strength after doping verified by hysteresis loop can provide further driving force for charge carrier migration. Benefitting from these optimized properties, under the optimum doping concentration, the photocatalytic degradation rate of antibiotic tetracycline hydrochloride and organic dye rhodamin B under visible light were about 1.6 times and 2.1 times of that in pure Bi3TiNbO9 respectively, outperforming the benchmark P25 and the majority of bismuth layer structured ferroelectrics. This work shed light on the feasibility of defect engineering and ferroelectric polarization modulation for efficient ferroelectric photocatalysts development.