MOF-derived NiO/γ-Fe2O3 p–n heterojunctions for ethylene glycol sensing

Abstract

The development of high-performance gas sensors for ethylene glycol (EG) detection is critical for industrial safety and environmental monitoring. Herein, we present a NiO/γ-Fe₂O₃ p–n heterojunction sensor engineered via calcining bimetallic ferrocene-based metal–organic framework (MOF) precursors, forming interfaces with tailored oxygen vacancies and hierarchical mesopores. This unique architecture synergizes strain-enhanced adsorption, porosity-mediated diffusion, and interfacial charge separation, driven by complementary electronic structures and dual Ni²⁺/Fe³⁺ catalytic activation. The optimized Ni/Fe-450 sensor exhibits exceptional performance: a record response of 102 to 100 ppm EG at 200 °C, 25-fold selectivity over ethanol, and <4% signal decay over 28 days. Mechanistic studies reveal that oxygen vacancies and adsorbed O⁻ species dominate the surface reactions, while the built-in electric field at the heterojunction amplifies resistance modulation. This work establishes a defect–porosity–functionality co-design strategy, bridging molecular-level catalysis with macroscopic charge transport, and advances high-performance chemical sensors for toxicant monitoring.