Deep eutectic solvents as active media for the preparation of highly conducting 3D free-standing PANI xerogels and their derived N-doped and N-, P-codoped porous carbons

Abstract

This work reports on the preparation of PANI in the form of highly conducting free-standing xerogels by controlling the synthetic process from the selection of precursors and cross-linkers to the dopant acid. This novel synthesis was carried out using polymerizable deep eutectic solvents (DESs) composed of anilinium chloride (AHCl) as hydrogen bond acceptor and ethylene glycol, glycerol or glycolic acid as hydrogen bond donors in the absence of any further solvent. The addition of p–phenylenediamine and a post-synthetic cross-linking process allowed the achievement of structurally stable xerogels by avoiding the occurrence of microscopic cracks during drying while preserving a suitable oxidation state and doping level. These features were critical to obtain PANI xerogels with a remarkably high electrical conductivity of ca. 1.17 S cm−1. Finally, given the intrinsic nitrogen content of PANI xerogels and phosphorus content resulting from cross-linking with phytic acid, some of these samples were carbonized to produce monolithic N-doped and N,P-codoped porous carbons, which were found to be suitable catalysts for the oxygen reduction reaction via a nearly-four-electron mechanism.