Electrochemical gas sensors based on polypyrrole-porous silicon

► Polymerization of pyrrole into regularly nanostructured Si/PS and Si/oxide PS from CH3CN solution was investigated. ► The polymerization process showed different characteristic stages in both potential and current transients. ► The oxidation of PS has a preferential nucleation of PPy at the pore bottom, and deposition of PPy inside the pores followed by polymerization at the outer surface. ► The results presented in this work show that Si/oxide PSi/PPy and Si/PS/PPy structures can be used as a sensor for CO2 gas. ► These sensors are extremely sensitive, have a good response and recovery time.