Pd-doped TiO2@polypyrrole core-shell composites as hydrogen-sensing materials

A core-shell composite consisting of polypyrrole (PPy) nanofibers and TiO2 was synthesized by using PPy nanofibers as the core and TiO2 as the shell. The TiO2@PPy composite substrate was doped with Pd nanoparticles via chemical reduction. The resulting Pd-TiO2@PPy nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Brunauer-Emmett-Teller (BET) adsorption analysis before it was utilized to fabricate a hydrogen sensor. Compared with sensors based on TiO2@PPy or PPy, the Pd-TiO2@PPy sensor was highly sensitive and selective to hydrogen gas, exhibiting a fast response time in air at room temperature. The Pd-TiO2@PPy-based sensor exhibited a sensitivity of 8.1% toward 1 vol% of H2 gas, which is much larger than the sensitivities of sensors based on only TiO2@PPy and PPy nanofibers. The excellent reproducibility, stability and selectivity of the Pd-TiO2@PPy nanocomposite make it a high potential candidate for hydrogen sensors.