Ferroelectric Oxide Nanocomposites with Trimodal Pore Structure for High Photocatalytic Performance

An effective method to improve the photocatalytic performances of powder catalysts is to use the internal electric field from ferroelectrics to separate photogenerated charge carriers. The design and engineering of a complex hetero-junction with a hierarchical pore structure is highly desirable for the efficient application of ferroelectric materials in photocatalysis. Here, we present a novel strategy using two templates to fabricate PbTiO₃/TiO₂/carbon (PTC) nanocomposites with a tunable microstructure. A hard SiO₂ template combined with an ice template followed by an appropriate pyrolysis procedure introduced trimodal (micro-, meso-, macro-) porosity. The as-prepared PTC nanocomposites with optimal mass ratio exhibited excellent photocatalytic and photoelectrochemical performances. PbTiO₃/TiO₂ annealed at 900 °C (PTC-900) showed a MB degradation rate of 0.21 and 0.021 min^-1 under UV and visible light irradiation, which are, respectively, 7.2 and 3 times those of pure PbTiO₃. The photocurrent density of the composite catalyst is 1.48 mA cm^-2 at the potential of 1.0 V versus saturated calomel electrode, and the rates of hydrogen generation of PTC-900 are as high as 2360 and 9.6 μmol h^-1 g^-1 under UV and visible light irradiation, respectively. More importantly, the simultaneous application of ultrasound-induced mechanical waves further improved the photocatalytic reactivity. This work serves to improve understanding on the design of ferroelectric/piezoelectric photocatalysts with a hierarchical pore structure and also proposes a widely applicable strategy for the fabrication of high-performance micro-nano/nano-nano structures.