Fabrication of ZIF-8 encapsulated ZnO microrods with enhanced sensing properties for H₂ detection

As one of the most typical fault characteristic gases in transformer oil, the content of H₂ is an important criterion for judging the operation state of power transformers; while online monitoring of such species through gas sensing technology could effectively detect latent faults and avoid accidents. Zinc oxide is a popular sensing material in recent years with limited sensitivity, selectivity and stability for gas detection, while zeolite imidazolate framework-8 (ZIF-8), one kind of metal–organic frameworks (MOFs) materials, possesses adjustable porosity, huge specific surface areas and good thermal stability, so it could perfectly remedy those defects. This paper studied gas-sensing properties of ZnO rods encapsulated by ZIF-8 (ZnO@ZIF-8) for H₂. The morphologies, structures, and composition were characterized in detail by means of X-ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and energy disperse spectroscopy. H₂ gas sensing properties of pure ZnO and ZnO@ZIF-8 composites were implemented based on gas sensing platform. Results suggested that the ZnO@ZIF-8 showed better sensitivity, selectivity and stability than pure ZnO rods, and meanwhile possessed lower optimum operating temperature upon H₂ detection. Meanwhile the gas-sensing mechanism was analyzed comprehensively from three aspects of sensitivity, selectivity and stability. Our aim of this work is to propose a novel core–shell material with enhanced performance for H₂ sensing and provide a new idea for developing high-performance materials to detect fault characteristic gases.