The synthesis of polyacrylonitrile (PAN) with precisely defined morphology is essential to obtain a polymer precursor for the preparation of high-value carbon-based materials. PAN homopolymers with very narrow molecular weight distribution were prepared by electrochemically mediated atom transfer radical polymerization (eATRP) of acrylonitrile. The redox properties of the Cu complexes used as eATRP catalysts were first investigated. Convenient polymerization conditions were identified by varying the applied potential, initiator nature, monomer and catalyst loading, and targeted molecular weight (MW). PAN with high MW, 9.1 x10(4) g mol(-1), was obtained in only 3 h. A shorter PAN was extended with butyl acrylate to prepare a well-defined PAN-b-PBA copolymer, which was subjected to annealing and pyrolysis. The obtained copolymer-templated nitrogen-enriched nanocarbon was characterized by BET, TEM and Raman spectroscopy. The material showed an exceptionally high nitrogen content, together with a remarkable activity toward O-2 reduction and 40% selectivity for H2O2 production. (C) 2018 Elsevier Ltd. All rights reserved.