Strategic Synthesis of SiO2-ModifiedPorous Co3O4 Nano-Octahedra Through the NanocoordinationPolymer Route for Enhanced and Selective Sensing of H2 Gasover NOx

摘要

In this work, a strategic synthesis of Co3O4 nano-octahedra was developed through the facile nanoscale coordination polymer (NCP) route, which was further modified by SiO2 to be used as a sensor for enhanced sensing of hydrogen. The Co(II)-NCP-derived Co3O4 octahedra and SiO2-modified Co3O4 octahedra were characterized using Fourier transform infrared, powder X-ray diffraction, Brunauer–Emmett–Teller, thermogravimetric analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed reduction (H2TPR) techniques. The SiO2-modified Co3O4 sensor exhibited a stronger and selective electrical response to H2 gas over NOx at 225 °C than Co(II)-NCP-derived Co3O4 octahedra and the conventional Co₃O₄ powder. The composite sensor shows faster recovery and significant repeatability than the other two. The enhancement in the sensing performance of the SiO₂-modified Co₃O₄ octahedron was explained by the effectiveness of surface modification, controlled morphology, and combination of synergistic effect of Co₃O₄ and SiO₂. Surface engineering of the as-prepared Co₃O₄ nano-octahedra with an exposed (111) surfaceplane and later SiO₂ modification facilitates effectivegas adsorption, resulting in enhancement in sensing and selectivityover NO_x. The details of the synergisticeffect and the plausible reasons for the improvement in gas-sensingparameters are discussed here. This study would offer new directionsfor development on the controlled synthesis of porous materials, ingeneral, and in gas sorption or sensing, in particular.