Polarization-Induced\nInternal Electric Field-Dominated\nS‑Scheme KNbO<sub>3</sub>–CuO Heterojunction for Photoreduction\nof CO<sub>2</sub> with High CH<sub>4</sub> Selectivity

The polarization-induced internal electric field (IEF)\nin ferroelectric\nmaterials could promote photogenerated charge transfer across the\nheterojunction interface, but the effect of polarization-induced IEF\non the mechanism of photogenerated charge transfer is ambiguous. In\nthis study, a KNbO<sub>3</sub>–CuO heterojunction was synthesized\nby depositing copper oxide (CuO) onto KNbO<sub>3</sub>. Incorporating\nCuO broadens the light absorption of KNbO<sub>3</sub>, thereby enhancing\nthe dissociation of the photogenerated charges. The results show that\nthe polarization-induced IEF in KNbO<sub>3</sub> determines that the\ncharge transport mechanism in the KNbO<sub>3</sub>–CuO heterojunction\nfollows the S-scheme. Owing to the S-scheme heterojunctions and efficient\nCO<sub>2</sub> capture and activation by CuO, the CH<sub>4</sub> production\nrate of KNbO<sub>3</sub>–CuO increased by nearly 26 times compared\nto KNbO<sub>3</sub>. Additionally, the CH<sub>4</sub> selectivity\nof KNbO<sub>3</sub>–CuO could reach up to 97.80%. This research\noffers valuable insights into enhancing the photogenerated charge\nseparation and constructing heterojunctions.