CO₂ Electrochemical Reduction to Hydrocarbon Fuels on Carbon-Supported Copper Nanoparticles: Support Effect

Previously, we reported activity and selectivity of Cu nanoparticles towards CO 2 electroreduction to hydrocarbon fuels (CH 4 and C 2 H 4 ) on three different supports (Vulcan Carbon (VC), Ketjenblack (KB) and singled walled carbon nanotubes (SWCNT)) 1 . We found that carbon materials not only serve as inert supports, but are actively involved in electrochemical CO 2 reduction likely due to hydrogen spillover from the support to the surface of Cu nanoparticles. Here we explore the effect of carbon support on the product distribution in CO 2 electroreduction reaction in more detail expanding the number of nanostructered supports to reduced graphene oxide (rGO), and onion-like carbon (OLC) 3 . These five carbon materials (VC, KB, SWCNT, rGO and OLC) have different surface area, electronic conductivity, morphology, and inherent size. Cu nanoparticles of 15-25 nm diameters on different carbon supports were synthesized by the reduction of CuCl 2 using NaBH 4 in aqueous ethylene glycol solution (20% v/v). X-Ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used for nanoparticles ex-situ analysis. The catalytic activities and selectivity of supported Cu nanoparticles towards CO 2 electrochemical reduction to hydrocarbon fuels were evaluated using a sealed rotating disk electrode (RDE) setup connected to a gas chromatograph 1 . Cu nanoparticles supported on VC and OLC exhibited higher catalytic activity vs other catalysts towards CH 4 and C 2 H 4 generation, respectively, between -1.4 and -1.6 V (vs Ag/AgCl reference electrode). At a more negative potential of -1.6 V, all five Cu catalysts promoted generation of both CH 4 and C 2 H 4 , with the higher selectivity in terms of Faradaic efficiencies towards C 2 H 4 formation. The C 2 H 4 /CH 4 ratio increased by almost an order of magnitude in the following order: Cu/VC (2.6:1) <Cu/KB (4.5:1) < Cu/SWNT (5.8:1) < Cu/GPO (10.8:1)< Cu/OLC (33:1). Cu/OLC showed both the lowest onset potential and the greatest selectivity towards C 2 H 4 formation. This presentation will discuss the reasoning behind the different catalytic activity and selectivity of supported Cu nanoparticles in catalyzing the CO 2 electrochemical reduction reaction. [1] O. A. Baturina, Q. Lu, M. A. Padilla, L. Xin, W. Li, A. Serov, K. Artyushkova, P. Atanassov, F. Xu, A. Epshteyn, T. Brintlinger, M. Schuette, and G. E. Collins, ACS Catal . 2014, 4, 3682. [2] P. V. Kamat, J. Phys. Chem. Lett . 1 (2010), 520. [3] J. K. McDonoug, Y Gogotsi, Interface , 22 (2013), 61.