Inorganic–Organic Bi₄Nb_1–<i>x</i>Ta_<i>x</i>O₈Cl/rGO/SA-PTA Z-Scheme Heterojunction with a Third-Order Polarized Electric Field and a Fast Electron Transfer Channel for Photocatalytic Overall Water Splitting

The effective separation and rapid transfer of photogenerated charges in the hydrogen evolution photocatalyst (HEP) and oxygen evolution photocatalyst (OEP) are crucial for achieving overall water splitting. Here, a third-order polarization electric field composed of an internal electric field (InEF1), an internal electric field (InEF2), and a Z-scheme interface electric field (IfEF3) was formed by the flowable π electrons of rGO to couple the enhanced interlayer polarization in Bi4Nb1–xTaxO8Cl and the increased molecular dipole moment in perylene tetracarboxylic acid (SA-PTA). This third-order polarized electric field with full space coverage provided a continuous driving force for the effective separation of photogenerated charges from the interior to the surface of the OEP (Bi4Nb1–xTaxO8Cl) and then to the HEP (SA-PTA), resulting in a 3.6-fold increase in charge separation efficiency. Furthermore, in the inorganic–organic Bi4Nb1–xTaxO8Cl/rGO/SA-PTA Z-scheme heterojunction, SA-PTA was selectively anchored to rGO through hydrogen bonding and π–π stacking, thereby establishing a fast electron transfer channel between Bi4Nb1–xTaxO8Cl and SA-PTA, achieving flow of interface charges from the OEP to HEP, and shortening of the interface charge transfer time from 54.8 to 38.2 ps. Benefiting from the accelerated charge transfer kinetics and strong oxidation–reduction ability, Bi4Nb1–xTaxO8Cl/rGO/SA-PTA exhibited a high activity of water oxidation and overall water splitting. In water oxidation, the evolution rate of O2 was 31.6 μmol h–1, which was 18.6 times that of Bi4NbO8Cl. In the overall water splitting, the evolution rates of H2 and O2 were 3.7 and 1.9 μmol h–1, respectively, which were 5.2 times that of Bi4Nb1–xTaxO8Cl/SA-PTA. In conclusion, this work provides a guideline for regulating interface interactions and accelerating charge transfer kinetics.