Impact of heterostructures on hydrogen sulfide sensing: Example of core-shell CuO/CuFe2O4 nanostructures

Toxic and corrosive H2S gas is detected using chemoresistive sensors based on CuO/CuFe2O4 core-shell heterostructures, which are characterized by DC resistance measurements, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Exposure to various test gases (CO, H-2, NO2, VOCs) reveals low responses. However, unique reactivity towards H2S at low operating temperatures leads to accumulation of CuS clusters on the surface, which can connect to create a percolation path of high electric conductance. The core-shell heterostructures differ in their response to H2S, as the materials' shell (CuFe2O4) partly converts incoming H2S to its combustion products, effectively reducing the amount of H2S reaching the core structures. This behavior was observed for both pulsed and continuous exposure to H2S, making it an inherent property of the examined core-shell heterostructures. SEM images and EDX spectra reveal that the phase transition with subsequent regeneration have a strong impact on the morphology of the functional layer.