Abstract
Recently [1,2], we reported activity and selectivity of Cu nanoparticles for electroreduction of CO2 to hydrocarbon fuels (CH4 and C2H4) on three nanostructured supports: reduced graphene oxide (rGO), single walled carbon nanotubes (SWNT) and onion-like carbon (OLC) [3]. Cu/OLC catalyst was found to be superior to the other two catalysts in terms of stability, activity and selectivity towards C2H4generation. We propose that the unusual Cu/OLC catalyst design offers superior activity and stability. The nanostructured catalyst envelops a shell of OLC around Cu nanoparticles; this layering acts as a filter that protects the catalyst surface from undesirable adsorbed species. Herein, we examine the effect of nanostructured support on catalysts’ activity and selectivity in more detail. In addition, we determine whether supported Cu nanoparticles are durable enough to withstand potential excursions to open circuit potential, which are commonly encountered during CO2electrolysis. Cu nanoparticles of 15-25 nm diameters on different carbon supports were synthesized by the reduction of CuCl2 by NaBH4. This procedure was carried out in suspensions of carbon supports in aqueous ethylene glycol solutions (20% v/v). X-Ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS) and pair-distribution function (PDF) were used for ex-situanalysis of nanoparticles. The catalytic activities of supported Cu nanoparticles and their selectivities towards hydrocarbon generation were evaluated using (1) a sealed rotating disk electrode (RDE) setup connected to a gas chromatograph (GC) and (2) a scanning flow cell (SFC) coupled to differential electrochemical mass-spectrometer (DEMS) [4]. Durability of supported Cu nanoparticles was evaluated using SFC connected to inductively coupled plasma mass spectrometer (ICP-MS) setup [5]. Fig. 1 shows partial currents of H2 (A), CH4 (B), C2H4 (C),CH3OH (D) and CO2electroreduction reaction total currents (E) measured on Cu/OLC, Cu/SWNT and Vulcan Carbon-supported Cu (Cu/VC) catalysts in DEMS-SFC configuration. Cu/VC catalyst is shown as a reference. Structural HRTEM and PDF (Fig. 2) analysis shows long-range ordering of the Cu-OLC catalyst and confirms high crystallinity of synthesized Cu nanoparticles. This presentation will provide analysis of the effect of support on catalytic activity, selectivity and durability of Cu nanoparticles as applied to electrochemical CO2reduction.
Published Version
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