Synergistic One-Dimensional Conductive Pathways and Local Polarization Fields for Intrinsic Bulk Charge Separation in Nonpolar Oxide Photocatalysts

Understanding and controlling bulk charge carrier migration and separation remain central challenges in developing highly efficient photocatalysts. Herein, we establish a research framework that integrates crystallographic analysis with electronic structure characterization to identify intrinsic structural features enabling efficient bulk-phase charge transport and separation. We demonstrate that the Frontier orbitals of K3Nb3Ge2O13 (KNGO) are dominated by Nb-O bonding within interconnected NbO6 octahedra, forming confined one-dimensional conductive channels composed of parallel octahedral chains. Crucially, local structural distortions of individual NbO6 units spontaneously generate directional local polarization fields, despite the crystal belongs to a nonpolar space group. These local polarization fields are oriented perpendicular to the conductive pathways, providing an intrinsic driving force for bulk charge separation that is not captured by macroscopic polarization. Eventually, KNGO loaded with 1 wt % Pd exhibits a hydrogen evolution rate of 96.0(6) μmol/h in methanol aqueous solution, with an apparent quantum yield of 6.82% at 295 nm, validating the predicted bulk charge separation capability. A structurally related K3Ta3B2O12 further supports the generality of this mechanism. Overall, this work demonstrates that nonpolar oxides containing low-dimensional conductive pathways and local structural asymmetry can intrinsically achieve efficient bulk charge separation, offering a transferable structural criterion for designing high-performance photocatalysts.