Polarization-Induced Internal Electric Field-Dominated S-Scheme KNbO₃–CuO Heterojunction for Photoreduction of CO₂ with High CH₄ Selectivity

The polarization-induced internal electric field (IEF) in ferroelectric materials could promote photogenerated charge transfer across the heterojunction interface, but the effect of polarization-induced IEF on the mechanism of photogenerated charge transfer is ambiguous. In this study, a KNbO₃-CuO heterojunction was synthesized by depositing copper oxide (CuO) onto KNbO₃. Incorporating CuO broadens the light absorption of KNbO₃, thereby enhancing the dissociation of the photogenerated charges. The results show that the polarization-induced IEF in KNbO₃ determines that the charge transport mechanism in the KNbO₃-CuO heterojunction follows the S-scheme. Owing to the S-scheme heterojunctions and efficient CO₂ capture and activation by CuO, the CH₄ production rate of KNbO₃-CuO increased by nearly 26 times compared to KNbO₃. Additionally, the CH₄ selectivity of KNbO₃-CuO could reach up to 97.80%. This research offers valuable insights into enhancing the photogenerated charge separation and constructing heterojunctions.