Abstract
In this work, Fe2O3/Co3O4 heterostructures were prepared via the ion-exchange between Co-MOFs template and Fe3+. At room temperature (25 °C), gas-sensing measurements revealed the Fe2O3/Co3O4 composites showed high response (Ra/Rg =2.54, 97.0 ppm), excellent selectivity and low detection limit (0.97 ppm) to NOx. The special oxygen temperature-programmed desorption (O2-TPD) and hydrogen temperature-programmed reduction (H2-TPR) curves indicated addition of Fe not only damaged the structure, but also increased the active sites of composites. Mott-Schottky (MS) plots testing and Electrochemical Impedance Spectroscopy (EIS) analysis were used to further quantitatively analyze the effect of Fe content on carrier density (Nd) and charge transfer resistance (Rct). The enhanced sensing mechanism of Fe2O3/Co3O4 composites were attributed to the as-formed heterojunctions that offered numerous diffusion channels and the additional modulation of resistance. By employing a facile MOFs hybrid-assisted method to design heterojunction composites, this work comprehensively analyzed the influence of heterogeneous structure on gas sensitivity, providing insights into the understanding of heterojunction gas sensor materials.
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