An electrochemical deposition technique was developed to realize high yield and selective synthesis of target carbon nanomaterials. The electrochemical reduction of halogenated carbons, such as carbon tetrachloride, in an ionic liquid was found to result in the formation of a thick graphitic carbon film over a Ni substrate, whereas polyacetylene formation was confirmed in the presence of a small amount of H2O. Such a novel high yield, selective carbon synthesis is expected to be a promising technique for the design of various carbon nanomaterials. (C) 2015 Elsevier Ltd. All rights reserved.