Synergistic regulation of BFe2O4/Fe2O3 (B = Mn, Co, Ni, Cu) nanoarray materials by crystal plane and interface engineering for highly selective detection of 2-CEES gas

Mustard gas is a highly toxic chemical warfare agent. Hence, the development of a real-time and fast sensor for detecting 2-chloroethyl ethyl sulfide (2-CEES), a simulant of mustard gas, is a critical challenge. In this study, a novel BFe₂O₄/Fe₂O₃ (B = Mn, Co, Ni, Cu) nanoarray structure with an optimal heterointerface and an active crystal plane was constructed using an in-situ controllable solvothermal method, through regulating the B sites in the Fe-based inverse spinel. Among them, the NiFe₂O₄/Fe₂O₃ sensor exhibits ultra-high response (S 124.3) and ultra-short response time (3.2 s) to 100 ppm 2-CEES at 170 °C, with an extremely low detection limit (0.01 ppm). Through the analysis of the sensing mechanism, it is confirmed that in NiFe₂O₄/Fe₂O₃, the NiFe₂O₄ exposes a highly active (111) crystal plane, forms Ni active sites, and constructs an optimized heterointerface with Fe₂O₃. These features synergistically accelerate electron transfer, increase the surface-adsorbed oxygen species, and promote the adsorption and diffusion of 2-CEES on the sensitive layer. This work provides a universal and facile strategy for designing bimetallic/multimetallic oxide sensing materials with heterostructures and an active crystal plane.