Surface oxygen vacancy engineering in weak Bi-O bonded ferroelectric bismuth sodium titanate for boosting the photocatalytic CO₂ reduction reaction

Photocatalytic conversion of CO2 into renewable fuels is an exciting and challenging approach to mitigate carbon emissions and the energy crisis. The efficiency is hindered by the insufficient carrier transport capacity and high electron-hole pair complexation of the catalysts. The inherent spontaneous polarization in ferroelectric materials can affect the generation, transportation, and isolation of intermediates within catalytic reactions in modulating the pace and effectiveness of photocatalytic processes. Herein, ferroelectric bismuth sodium titanate (BNT) decorated with oxygen vacancies (OVs) via in situ reduction is first explored to promote the photocatalytic CO2 reduction reaction (CO2RR). The chemical states and coordination environment of the cations and OVs are elaborated by using the X-ray absorption fine structure to probe weakened Bi-O bonds and enhanced lattice distortion. Besides built-in electric fields originating from intrinsic spontaneous polarization, carrier dynamics and reactive sites are optimized with extended visible light absorption thanks to the special morphology and OVs. Remarkably, oxygen defected catalysts show 18 times higher CO reduction yield than pristine BNT, outperforming state-of-the-art bulk ferroelectrics for photocatalytic CO2RR. Interestingly, the product selectivity can be tailored after a poling treatment. This work provides a systematic approach for designing efficient ferroelectric photocatalysts, and meanwhile, expands the ferroelectric photocatalyst family for advancing CO2 conversion.