Interfacial charge transfer mechanism of p-n PdO/ZnO heterojunctions for high-performance non-enzymatic glucose sensing.

In this work, p-type PdO nanoparticle-decorated n-type ZnO nanorods (PdO NPs/ZnO NRs) were synthesized via a facile hydrothermal method and used as a representative p-n heterojunction model to investigate interfacial charge transfer during electrochemical glucose oxidation. The PdO NP/ZnO NR/glassy carbon electrode exhibited high electrocatalytic activity for glucose oxidation, with a wide linear range of 0.1-10.0 mM, a sensitivity of 523.3 µA mM-1 cm-2, and a calculated detection limit of 0.0868 mM. The sensor also demonstrated good reproducibility, repeatability, storage stability, and selectivity. An energy band model was proposed to elucidate the charge transfer mechanism at the p-n PdO/ZnO heterointerface. Fermi-level equilibration is expected to induce band bending and built-in electric field formation, whereas glucose oxidation is proposed to dynamically modulate the depletion region, thereby promoting directional carrier transport and accelerating interfacial electron transfer kinetics. This work provides mechanistic insight into heterojunction-regulated charge transfer and offers a rational strategy for designing advanced semiconductor heterostructures for high-performance electrochemical biosensing.