A fast and sensitive catalytic gas sensors for hydrogen detection based on stabilized nanoparticles as catalytic layer

Miniaturized micro-machined catalytic gas sensors offer great advantages regarding power consumption and response time. In combination with a porous catalyst layer high sensitivity can be achieved. However, often this approach does not provide sufficient long-term stability. In this article a miniaturized catalytic gas sensor for hydrogen detection is presented based on colloidally prepared and stabilized platinum nanoparticles as a catalytic layer. Due to its miniaturized design and the highly porous catalyst, a very short response time of <150 ms is achieved. Furthermore, the high free reactive surface of the stabilized nanoparticles, the direct contact to the sensor and a high seebeck coefficient enable to accomplish a high resolution and high sensitivity of about 0.22 mV/10 ppm, whereas the power consumption is significantly lowered. As thermally induced sintering of the nanoparticles leads to deactivation of the catalyst, an approach is used where the nanoparticles are linked via organic molecules (ligands) binding to the particle surface to form a highly porous “ligand-linked” nanoparticle network. As a consequence, particle sintering is significantly reduced and the adhesion to the substrate is improved so that a highly improved stability compared to sensors fabricated with unstabilzed catalysts is achieved. We furthermore show that the use of these novel materials enables to reduce the influence of humidity on the sensor performance. Additionally, the sensor design allows for a precise control of the catalyst temperature. Hence, thermal loading by autocatalytic effects that may lead to catalyst deactivation via unwanted side reactions can be reduced, enabling for an additional improvement of the catalyst lifetime.