Nitrile chain reactions for cyano-based ionic liquid derived mesoporous carbon as efficient bifunctional electrocatalyst

Abstract

Different from the intermediate nitrile cyclotrimerization reactions, a new nitrile chain reaction is proposed to interpret the condensation and carbonization process of cyano-based ionic liquids [MCNIm][TFSI] which is used as a model precursor. The nitrile chain reaction forms several oligomers including dimers, trimers and tetramers during the condensation process at low temperature. The results show the oligomers are pyrolyzed to small fragments at high temperature undergoing a variety of cross-linking and recombination to produce more stable benzene and pyridine based polycyclic aromatic groups prior to the final mesoporous carbon material formation. The cyano-based ionic liquids and nitrile chain reaction mechanism readily yields mesoporous carbon with a specific surface area of 1050 m2 g−1 and a high co-doping with N and S and a content of graphitized material. In terms of potential applications, the N, S-codoped mesoporous carbon material facilitates excellent bifunctional electrocatalytic activity toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) comparable to the benchmark of those commercial 20 wt% Pt/C and RuO2 catalysts, respectively. Remarkably, our analyses show bis(trifluoromethanesulphonyl)-imide (TFSI) anions display much better thermal stability than imidazolium cations, which suggests future potential for other functional cations with more thermally stable intermediate polymeric structures.