Ultrasonic cavitation enhanced photocatalytic CO2 reduction by superior flexible black BaTiO3 nanofibers

Photocatalytic CO2 reduction is an attractive strategy to realize carbon–neutral economy but is challenging by its low efficiency and uncontrollable selectivity. Here, we report a new flexible black BaTiO3 nanofiber (B-BTO NF) and prove its unique function of ultrasonic cavitation enhanced photocatalytic CO2 reduction into controllable syngas. The B-BTO NFs with a large deformation ability and a high mechanical strength contain unsaturated Ti3+ coordination and vacancy defects. Under ultrasound, the NF film gathers abundant cavitation bubbles, and the continual explosions of these bubbles bring periodic piezoelectric polarization changes and release net charges on B-BTO NFs, thus triggering photocatalytic CO2 reduction into syngas. Moreover, the product selectivity can be controlled by facilely adjusting the ultrasonic frequency and power. As a result, the evolution rate of target syngas (CO/H2 ≈ 1:1.3) reaches as high as 12525 μmol/g/h. The proposed flexible B-BTO NF induced ultrasonic cavitation-enhancement strategy provides new insights for designing photocatalysts.