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

Monday, October 12, 2015: 14:00
Remington C (Hyatt Regency)
Q. Lu (Naval Research Laboratory), A. Purdy (Naval Research Laboratory), B. Dyatkin (Drexel University), Y. Gogotsi (Drexel University), and O. A. Baturina (Naval Research Laboratory)
Previously, we reported activity and selectivity of Cu nanoparticles towards CO2 electroreduction to hydrocarbon fuels (CH4 and C2H4) 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 CO2 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 CO2 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 CuCl2 using NaBH4 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 CO2 electrochemical reduction to hydrocarbon fuels were evaluated using a sealed rotating disk electrode (RDE) setup connected to a gas chromatograph1.

Cu nanoparticles supported on VC and OLC exhibited higher catalytic activity vs other catalysts towards CH4 and C2H4 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 CH4 and C2H4, with the higher selectivity in terms of Faradaic efficiencies towards C2H4 formation. The C2H4/CH4  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 C2H4 formation. 

This presentation will discuss the reasoning behind the different catalytic activity and selectivity of supported Cu nanoparticles in catalyzing the CO2 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.