Semiconducting Conjugated Microporous Polymer: An Electrode Material for Photoelectrochemical Water Splitting and Oxygen Reduction

Intriguing structural design and inherent nanoporosity of conjugated microporous polymers (CMP) with extended pi-conjugation have stimulated research interest in exploring their applications to solve challenging environmental and energy problems. However, only few attempts are made so far to identify the semiconducting properties of these CMP networks having direct relevance to energy conversion, electronic devices and photocatalysis. The present study identifies the semiconducting properties of a conjugated microporous polymer, namely, poly(1,3,5-triethynylbenzene) (PTEB) in detail using photoluminescence, UV-Visible absorption, Kelvin probe force microscopy, cyclic voltammetry, Mott-Schottky analysis and photoelectrochemical studies. Integration of heteroatoms such as nitrogen into the polymer network by post-thermal treatment is shown to enhance significantly the activities towards oxygen reduction reaction. A drastic improvement in the activity of PTEB observed on nitrogen incorporation into the carbon skeleton is attributed to an increase in the number of electrochemical active sites and increase in its pore size. The systematic evaluation of conducting properties of CMP materials promises future development of electronic, electrochemical and photoelectrochemical devices.