Strengthening PPy/TiO₂ arrayed SiOC honeycombs for self-protective gas sensing

As the operation reliability for gas sensors under complex environments is in increasing demand, the stability and safety performance are significant besides qualified gas sensing properties. In this work, structural-strengthened and self-protective ammonia sensing micro-tunnels were constructed by 3D printing. Modified methyl-silsesquioxane (MK) resin was employed as the feedstock to build the SiOC honeycomb structures. Polypyrrole (PPy) nanoparticle decorated TiO₂ arrays sensitized the structures to form inner gas-sensitive tunnels. The sensing structure exhibited high selectivity toward ammonia at room temperature. Response to 50 ppm NH₃ was 18.67%, while the response and recovery times were 119 and 86 s, respectively. The excellent long-term stability also ensured reliable operation in complex environments. More importantly, the enhanced honeycomb had an outstanding mechanical performance with the compressive strength, Young's modulus, and energy absorption of 33.72 MPa, 2.40 GPa, and 28.22 kJ/m³, respectively. It can serve as a load-bearing part of the fundamental component to avoid catastrophic collapse while maintaining a regular sensing capability under pressure loading as the excellent deformation resistance ensured the integrity and connection of the sensing layer. Moreover, the inner through-holes facilitated the exposure of the sensing tunnels to the atmosphere, which can detect target gas simultaneously without the embedding of extra sensors. Thus, the construction of self-protective gas sensing structures was promising to be an efficient strategy for reliable gas detection in extreme environments.