The　effect　of　support　on　electrocatalytic　activity　of　Cu　nanoparticles　(NPs)　towards　CO2　electroreduction　to　hydrocarbon　fuels　(CH4　and　C2H4)　is　investigated　for　three　types　of　nanostructured　carbons:　single　wall　carbon　nanotubes　(SWNT),　reduced　graphene　oxide　(RGO)　and　onion-like　carbon　(OLC).　Cu/SWNT,　Cu/RGO　and　Cu/OLC　composite　catalysts　are　synthesized　and　characterized　by　X-ray　diffraction　analysis,　transmission　electron　microscopy　and　electrochemical　surface　area　measurements.　Electrocatalytic　activities　of　the　synthesized　materials,　as　measured　in　an　electrochemical　cell　connected　to　a　gas　chromatograph,　are　compared　to　that　of　Cu　NPs　supported　on　Vulcan　carbon.　All　four　catalysts　demonstrate　higher　activity　towards　C2H4　generation　vs　CH4,　with　production　of　the　latter　mostly　suppressed　on　Cu　NPs　supported　on　nanostructured　substrates.　Onset　potentials　for　C2H4　vs　CH4　generation　demonstrate　200 mV　positive　shifts　for　Cu/SWNT,　Cu/RGO,　and　Cu/OLC　catalysts.　The　Cu/OLC　catalyst　is　found　to　be　superior　to　the　other　two　nanostructured　catalysts　in　terms　of　stability,　activity　and　selectivity　towards　C2H4　generation.　Its　faradaic　efficiency　reached　60%　at　−1.8 V　vs　Ag/AgCl.　The　enhanced　stability　and　activity　of　the　Cu/OLC　catalyst　can　be　attributed　to　the　unique　catalyst　design,　wherein　a　shell　of　OLC　surrounds　the　Cu　NPs.　Such　a　configuration　enables　the　outer　layer　to　act　as　a　filter　that　protects　the　Cu　surface　from　adsorption　of　undesirable　species,　enhances　its　electrocatalytic　performance,　and　improves　its　viability　in　CO2　electroreduction　reaction.　The　enhanced　selectivity　of　the　Cu/OLC　catalyst　towards　the　C2H4　production　is　most　likely　related　to　the　enhanced　electrocatalytic　activity　of　the　OLC　support　towards　the　CO2　electroreduction　to　CO.　Higher　CO　surface　concentration　from　CO2　electroreduction　on　the　OLC　support,　rather　than　a　greater　number　of　available　sites　for　CO　dimerization,　likely　originated　this　behavior.　CO　molecules　generate　on　surfaces　of　OLCs,　dimerize　on　Cu　NP　(100)　planes,　and,　subsequently,　yield　additional　C2H4　molecules.　Both　the　reduction　of　the　CO2　to　CO　on　the　surface　of　OLCs　and　reduction　of　“extra”　CO　molecules　to　C2H4　on　the　surface　of　Cu　NPs　are　expected　to　lead　to　an　increase　in　the　local　pH,　which　is　also　beneficial　for　the　C2H4　production.　©　2016