Hierarchical porous hollow SnO2 nanofiber sensing electrode for high performance potentiometric H2 sensor

A planar mixed-potential sensor was prepared based on SnO2 sensing electrode of hierarchical porous hollow nanofibers. The electrode was featured by three-dimensional scaffold architecture with high porosity, large pore size, and excellent pore interconnectivity. A response value of −289.1 mV and response time of 5 s were achieved at 450 °C for 1000 ppm H2, which were 5 and 2.6 times better than those of a similar sensor with sensing electrode of SnO2 nanoparticles, respectively. The response values exhibited a linear or logarithmic dependence on the H2 concentration for below or above 140 ppm, respectively, corresponding to a change from diffusion- to reaction-controlled kinetics. Power-law concentration dependence was observed for the response time, which also exhibited a similar transition at 140 ppm. Moreover, excellent selectivity, long-term stability, and repeatability were achieved. The morphology-dependent sensing behavior was discussed in terms of the diffusion-reaction process and Thiele modulus. These results highlight the importance of morphology to mixed-potential gas sensors, and show that hierarchical nanofiber electrode is desirable for achieving high gas sensing performance.